O Telescópio Espacial Hubble das agências NASA e ESA registrou a imagem pela primeira vez da explosão prevista de uma supernova. O reaparecimento da supernova Refsdal foi calculado a partir de diferentes modelos de aglomerados de galáxias, cuja imensa gravidade está entortando a luz da supernova.
Muitas estrelas terminam a sua vida com uma explosão, mas somente poucas dessas explosões estelares têm sido registradas no ato que acontecem. Quando isso acontece, é pura sorte, pelo menos até agora. No dia 11 de Dezembro de 2015, os astrônomos não somente fizeram a imagem de uma supernova em ação, como também observaram quando e onde ela estava prevista para acontecer.
A supernova, apelidada de Refsdal, foi registrada no aglomerado de galáxias, conhecido como MACS J1149.5+2223. Enquanto que a luz do aglomerado gasta cerca de cinco bilhões de anos para chegar até nós, a supernova explodiu muito tempo antes, a aproximadamente 10 bilhões de anos atrás.
A história da Refsdal começou em Novembro de 2014, quando os cientistas registraram quatro imagens separadas da supernova num raro arranjo conhecido como Cruz de Einstein, ao redor de uma galáxia dentro do MACS J1149.5+2223. A ilusão de óptica cósmica ocorreu devido ao fato da massa de uma única galáxia dentro do aglomerado estar entortando e ampliando a luz da distante explosão estelar, num processo conhecido como lente gravitacional.
Deja vu all_over_again_the_reapperance_of_supernova_refsdalSérgio Sacani
O Telescópio Espacial Hubble das agências NASA e ESA registrou a imagem pela primeira vez da explosão prevista de uma supernova. O reaparecimento da supernova Refsdal foi calculado a partir de diferentes modelos de aglomerados de galáxias, cuja imensa gravidade está entortando a luz da supernova.
Muitas estrelas terminam a sua vida com uma explosão, mas somente poucas dessas explosões estelares têm sido registradas no ato que acontecem. Quando isso acontece, é pura sorte, pelo menos até agora. No dia 11 de Dezembro de 2015, os astrônomos não somente fizeram a imagem de uma supernova em ação, como também observaram quando e onde ela estava prevista para acontecer.
A supernova, apelidada de Refsdal, foi registrada no aglomerado de galáxias, conhecido como MACS J1149.5+2223. Enquanto que a luz do aglomerado gasta cerca de cinco bilhões de anos para chegar até nós, a supernova explodiu muito tempo antes, a aproximadamente 10 bilhões de anos atrás.
A história da Refsdal começou em Novembro de 2014, quando os cientistas registraram quatro imagens separadas da supernova num raro arranjo conhecido como Cruz de Einstein, ao redor de uma galáxia dentro do MACS J1149.5+2223. A ilusão de óptica cósmica ocorreu devido ao fato da massa de uma única galáxia dentro do aglomerado estar entortando e ampliando a luz da distante explosão estelar, num processo conhecido como lente gravitacional.
We report the discovery of a new Kepler transiting circumbinary planet (CBP).
This latest addition to the still-small family of CBPs defies the current trend of known
short-period planets orbiting near the stability limit of binary stars. Unlike the previous
discoveries, the planet revolving around the eclipsing binary system Kepler-1647 has
a very long orbital period ( 1100 days) and was at conjunction only twice during
the Kepler mission lifetime. Due to the singular configuration of the system, Kepler-
1647b is not only the longest-period transiting CBP at the time of writing, but also one
of the longest-period transiting planets. With a radius of 1:060:01 RJup it is also the
largest CBP to date. The planet produced three transits in the light-curve of Kepler-
1647 (one of them during an eclipse, creating a syzygy) and measurably perturbed the
times of the stellar eclipses, allowing us to measure its mass to be 1:520:65 MJup.
The planet revolves around an 11-day period eclipsing binary consisting of two Solarmass
stars on a slightly inclined, mildly eccentric (ebin = 0:16), spin-synchronized
orbit. Despite having an orbital period three times longer than Earth’s, Kepler-1647b is
in the conservative habitable zone of the binary star throughout its orbit.
Beyond the Kuiper Belt Edge: New High Perihelion Trans-Neptunian Objects With...Sérgio Sacani
We are conducting a survey for distant solar system objects beyond the Kuiper
Belt edge ( 50 AU) with new wide-field cameras on the Subaru and CTIO tele-
scopes. We are interested in the orbits of objects that are decoupled from the
giant planet region in order to understand the structure of the outer solar sys-
tem, including whether a massive planet exists beyond a few hundred AU as first
reported in Trujillo and Sheppard (2014). In addition to discovering extreme
trans-Neptunian objects detailed elsewhere, we have found several objects with
high perihelia (q > 40 AU) that differ from the extreme and inner Oort cloud
objects due to their moderate semi-major axes (50 < a < 100 AU) and eccen-
tricities (e . 0.3). Newly discovered objects 2014 FZ71 and 2015 FJ345 have
the third and fourth highest perihelia known after Sedna and 2012 VP113, yet
their orbits are not nearly as eccentric or distant. We found several of these high
perihelion but moderate orbit objects and observe that they are mostly near Nep-
tune mean motion resonances and have significant inclinations (i > 20 degrees).
These moderate objects likely obtained their unusual orbits through combined
interactions with Neptune’s mean motion resonances and the Kozai resonance,
similar to the origin scenarios for 2004 XR190. We also find the distant 2008
ST291 has likely been modified by the MMR+KR mechanism through the 6:1
Neptune resonance. We discuss these moderately eccentric, distant objects along
with some other interesting low inclination outer classical belt objects like 2012
FH84 discovered in our ongoing survey.
WHERE IS THE FLUX GOING? THE LONG-TERM PHOTOMETRIC VARIABILITY OF BOYAJIAN’S ...Sérgio Sacani
We present ∼ 800 days of photometric monitoring of Boyajian’s Star (KIC 8462852) from the AllSky
Automated Survey for Supernovae (ASAS-SN) and ∼ 4000 days of monitoring from the All Sky
Automated Survey (ASAS). We show that from 2015 to the present the brightness of Boyajian’s Star
has steadily decreased at a rate of 6.3 ± 1.4 mmag yr−1
, such that the star is now 1.5% fainter than it
was in February 2015. Moreover, the longer time baseline afforded by ASAS suggests that Boyajian’s
Star has also undergone two brightening episodes in the past 11 years, rather than only exhibiting a
monotonic decline. We analyze a sample of ∼ 1000 comparison stars of similar brightness located in
the same ASAS-SN field and demonstrate that the recent fading is significant at & 99.4% confidence.
The 2015 − 2017 dimming rate is consistent with that measured with Kepler data for the time period
from 2009 to 2013. This long-term variability is difficult to explain with any of the physical models
for the star’s behavior proposed to date
TEMPORAL EVOLUTION OF THE HIGH-ENERGY IRRADIATION AND WATER CONTENT OF TRAPPI...Sérgio Sacani
The ultracool dwarf star TRAPPIST-1 hosts seven Earth-size transiting planets, some of which could
harbour liquid water on their surfaces. UV observations are essential to measure their high-energy
irradiation, and to search for photodissociated water escaping from their putative atmospheres. Our
new observations of TRAPPIST-1 Ly-α line during the transit of TRAPPIST-1c show an evolution of
the star emission over three months, preventing us from assessing the presence of an extended hydrogen
exosphere. Based on the current knowledge of the stellar irradiation, we investigated the likely history
of water loss in the system. Planets b to d might still be in a runaway phase, and planets within the
orbit of TRAPPIST-1g could have lost more than 20 Earth oceans after 8 Gyr of hydrodynamic escape.
However, TRAPPIST-1e to h might have lost less than 3 Earth oceans if hydrodynamic escape stopped
once they entered the habitable zone. We caution that these estimates remain limited by the large
uncertainty on the planet masses. They likely represent upper limits on the actual water loss because
our assumptions maximize the XUV-driven escape, while photodissociation in the upper atmospheres
should be the limiting process. Late-stage outgassing could also have contributed significant amounts
of water for the outer, more massive planets after they entered the habitable zone. While our results
suggest that the outer planets are the best candidates to search for water with the JWST, they also
highlight the need for theoretical studies and complementary observations in all wavelength domains
to determine the nature of the TRAPPIST-1 planets, and their potential habitability.
Keywords: planetary systems - Stars: individual: TRAPPIST-1
EXTINCTION AND THE DIMMING OF KIC 8462852Sérgio Sacani
To test alternative hypotheses for the behavior of KIC 8462852, we obtained measurements of the star
over a wide wavelength range from the UV to the mid-infrared from October 2015 through December
2016, using Swift, Spitzer and at AstroLAB IRIS. The star faded in a manner similar to the longterm
fading seen in Kepler data about 1400 days previously. The dimming rate for the entire period
reported is 22.1 ± 9.7 milli-mag yr−1
in the Swift wavebands, with amounts of 21.0 ± 4.5 mmag in
the groundbased B measurements, 14.0 ± 4.5 mmag in V , and 13.0 ± 4.5 in R, and a rate of 5.0 ± 1.2
mmag yr−1 averaged over the two warm Spitzer bands. Although the dimming is small, it is seen at
& 3 σ by three different observatories operating from the UV to the IR. The presence of long-term
secular dimming means that previous SED models of the star based on photometric measurements
taken years apart may not be accurate. We find that stellar models with Tef f = 7000 - 7100 K and
AV ∼ 0.73 best fit the Swift data from UV to optical. These models also show no excess in the
near-simultaneous Spitzer photometry at 3.6 and 4.5 µm, although a longer wavelength excess from
a substantial debris disk is still possible (e.g., as around Fomalhaut). The wavelength dependence of
the fading favors a relatively neutral color (i.e., RV & 5, but not flat across all the bands) compared
with the extinction law for the general ISM (RV = 3.1), suggesting that the dimming arises from
circumstellar material
Deja vu all_over_again_the_reapperance_of_supernova_refsdalSérgio Sacani
O Telescópio Espacial Hubble das agências NASA e ESA registrou a imagem pela primeira vez da explosão prevista de uma supernova. O reaparecimento da supernova Refsdal foi calculado a partir de diferentes modelos de aglomerados de galáxias, cuja imensa gravidade está entortando a luz da supernova.
Muitas estrelas terminam a sua vida com uma explosão, mas somente poucas dessas explosões estelares têm sido registradas no ato que acontecem. Quando isso acontece, é pura sorte, pelo menos até agora. No dia 11 de Dezembro de 2015, os astrônomos não somente fizeram a imagem de uma supernova em ação, como também observaram quando e onde ela estava prevista para acontecer.
A supernova, apelidada de Refsdal, foi registrada no aglomerado de galáxias, conhecido como MACS J1149.5+2223. Enquanto que a luz do aglomerado gasta cerca de cinco bilhões de anos para chegar até nós, a supernova explodiu muito tempo antes, a aproximadamente 10 bilhões de anos atrás.
A história da Refsdal começou em Novembro de 2014, quando os cientistas registraram quatro imagens separadas da supernova num raro arranjo conhecido como Cruz de Einstein, ao redor de uma galáxia dentro do MACS J1149.5+2223. A ilusão de óptica cósmica ocorreu devido ao fato da massa de uma única galáxia dentro do aglomerado estar entortando e ampliando a luz da distante explosão estelar, num processo conhecido como lente gravitacional.
We report the discovery of a new Kepler transiting circumbinary planet (CBP).
This latest addition to the still-small family of CBPs defies the current trend of known
short-period planets orbiting near the stability limit of binary stars. Unlike the previous
discoveries, the planet revolving around the eclipsing binary system Kepler-1647 has
a very long orbital period ( 1100 days) and was at conjunction only twice during
the Kepler mission lifetime. Due to the singular configuration of the system, Kepler-
1647b is not only the longest-period transiting CBP at the time of writing, but also one
of the longest-period transiting planets. With a radius of 1:060:01 RJup it is also the
largest CBP to date. The planet produced three transits in the light-curve of Kepler-
1647 (one of them during an eclipse, creating a syzygy) and measurably perturbed the
times of the stellar eclipses, allowing us to measure its mass to be 1:520:65 MJup.
The planet revolves around an 11-day period eclipsing binary consisting of two Solarmass
stars on a slightly inclined, mildly eccentric (ebin = 0:16), spin-synchronized
orbit. Despite having an orbital period three times longer than Earth’s, Kepler-1647b is
in the conservative habitable zone of the binary star throughout its orbit.
Beyond the Kuiper Belt Edge: New High Perihelion Trans-Neptunian Objects With...Sérgio Sacani
We are conducting a survey for distant solar system objects beyond the Kuiper
Belt edge ( 50 AU) with new wide-field cameras on the Subaru and CTIO tele-
scopes. We are interested in the orbits of objects that are decoupled from the
giant planet region in order to understand the structure of the outer solar sys-
tem, including whether a massive planet exists beyond a few hundred AU as first
reported in Trujillo and Sheppard (2014). In addition to discovering extreme
trans-Neptunian objects detailed elsewhere, we have found several objects with
high perihelia (q > 40 AU) that differ from the extreme and inner Oort cloud
objects due to their moderate semi-major axes (50 < a < 100 AU) and eccen-
tricities (e . 0.3). Newly discovered objects 2014 FZ71 and 2015 FJ345 have
the third and fourth highest perihelia known after Sedna and 2012 VP113, yet
their orbits are not nearly as eccentric or distant. We found several of these high
perihelion but moderate orbit objects and observe that they are mostly near Nep-
tune mean motion resonances and have significant inclinations (i > 20 degrees).
These moderate objects likely obtained their unusual orbits through combined
interactions with Neptune’s mean motion resonances and the Kozai resonance,
similar to the origin scenarios for 2004 XR190. We also find the distant 2008
ST291 has likely been modified by the MMR+KR mechanism through the 6:1
Neptune resonance. We discuss these moderately eccentric, distant objects along
with some other interesting low inclination outer classical belt objects like 2012
FH84 discovered in our ongoing survey.
WHERE IS THE FLUX GOING? THE LONG-TERM PHOTOMETRIC VARIABILITY OF BOYAJIAN’S ...Sérgio Sacani
We present ∼ 800 days of photometric monitoring of Boyajian’s Star (KIC 8462852) from the AllSky
Automated Survey for Supernovae (ASAS-SN) and ∼ 4000 days of monitoring from the All Sky
Automated Survey (ASAS). We show that from 2015 to the present the brightness of Boyajian’s Star
has steadily decreased at a rate of 6.3 ± 1.4 mmag yr−1
, such that the star is now 1.5% fainter than it
was in February 2015. Moreover, the longer time baseline afforded by ASAS suggests that Boyajian’s
Star has also undergone two brightening episodes in the past 11 years, rather than only exhibiting a
monotonic decline. We analyze a sample of ∼ 1000 comparison stars of similar brightness located in
the same ASAS-SN field and demonstrate that the recent fading is significant at & 99.4% confidence.
The 2015 − 2017 dimming rate is consistent with that measured with Kepler data for the time period
from 2009 to 2013. This long-term variability is difficult to explain with any of the physical models
for the star’s behavior proposed to date
TEMPORAL EVOLUTION OF THE HIGH-ENERGY IRRADIATION AND WATER CONTENT OF TRAPPI...Sérgio Sacani
The ultracool dwarf star TRAPPIST-1 hosts seven Earth-size transiting planets, some of which could
harbour liquid water on their surfaces. UV observations are essential to measure their high-energy
irradiation, and to search for photodissociated water escaping from their putative atmospheres. Our
new observations of TRAPPIST-1 Ly-α line during the transit of TRAPPIST-1c show an evolution of
the star emission over three months, preventing us from assessing the presence of an extended hydrogen
exosphere. Based on the current knowledge of the stellar irradiation, we investigated the likely history
of water loss in the system. Planets b to d might still be in a runaway phase, and planets within the
orbit of TRAPPIST-1g could have lost more than 20 Earth oceans after 8 Gyr of hydrodynamic escape.
However, TRAPPIST-1e to h might have lost less than 3 Earth oceans if hydrodynamic escape stopped
once they entered the habitable zone. We caution that these estimates remain limited by the large
uncertainty on the planet masses. They likely represent upper limits on the actual water loss because
our assumptions maximize the XUV-driven escape, while photodissociation in the upper atmospheres
should be the limiting process. Late-stage outgassing could also have contributed significant amounts
of water for the outer, more massive planets after they entered the habitable zone. While our results
suggest that the outer planets are the best candidates to search for water with the JWST, they also
highlight the need for theoretical studies and complementary observations in all wavelength domains
to determine the nature of the TRAPPIST-1 planets, and their potential habitability.
Keywords: planetary systems - Stars: individual: TRAPPIST-1
EXTINCTION AND THE DIMMING OF KIC 8462852Sérgio Sacani
To test alternative hypotheses for the behavior of KIC 8462852, we obtained measurements of the star
over a wide wavelength range from the UV to the mid-infrared from October 2015 through December
2016, using Swift, Spitzer and at AstroLAB IRIS. The star faded in a manner similar to the longterm
fading seen in Kepler data about 1400 days previously. The dimming rate for the entire period
reported is 22.1 ± 9.7 milli-mag yr−1
in the Swift wavebands, with amounts of 21.0 ± 4.5 mmag in
the groundbased B measurements, 14.0 ± 4.5 mmag in V , and 13.0 ± 4.5 in R, and a rate of 5.0 ± 1.2
mmag yr−1 averaged over the two warm Spitzer bands. Although the dimming is small, it is seen at
& 3 σ by three different observatories operating from the UV to the IR. The presence of long-term
secular dimming means that previous SED models of the star based on photometric measurements
taken years apart may not be accurate. We find that stellar models with Tef f = 7000 - 7100 K and
AV ∼ 0.73 best fit the Swift data from UV to optical. These models also show no excess in the
near-simultaneous Spitzer photometry at 3.6 and 4.5 µm, although a longer wavelength excess from
a substantial debris disk is still possible (e.g., as around Fomalhaut). The wavelength dependence of
the fading favors a relatively neutral color (i.e., RV & 5, but not flat across all the bands) compared
with the extinction law for the general ISM (RV = 3.1), suggesting that the dimming arises from
circumstellar material
The canarias einstein_ring_a_newly_discovered_optical_einstein_ringSérgio Sacani
We report the discovery of an optical Einstein Ring in the Sculptor constellation,
IAC J010127-334319, in the vicinity of the Sculptor Dwarf Spheroidal Galaxy. It is
an almost complete ring ( 300◦) with a diameter of 4.5 arcsec. The discovery was
made serendipitously from inspecting Dark Energy Camera (DECam) archive imaging
data. Confirmation of the object nature has been obtained by deriving spectroscopic
redshifts for both components, lens and source, from observations at the 10.4 m Gran
Telescopio CANARIAS (GTC) with the spectrograph OSIRIS. The lens, a massive
early-type galaxy, has a redshift of z = 0.581 while the source is a starburst galaxy
with redshift of z = 1.165. The total enclosed mass that produces the lensing effect
has been estimated to be Mtot = (1.86 ± 0.23) · 1012M⊙.
We present deep optical images of the Large and Small Magellanic Clouds (LMC and SMC) using
a low cost telephoto lens with a wide field of view to explore stellar substructure in the outskirts
of the stellar disk of the LMC (r < 10 degrees from the center). These data have higher resolution
than existing star count maps, and highlight the existence of stellar arcs and multiple spiral arms in
the northern periphery, with no comparable counterparts in the South. We compare these data to
detailed simulations of the LMC disk outskirts, following interactions with its low mass companion,
the SMC. We consider interaction in isolation and with the inclusion of the Milky Way tidal field.
The simulations are used to assess the origin of the northern structures, including also the low density
stellar arc recently identified in the DES data by Mackey et al. (2015) at ∼ 15 degrees. We conclude
that repeated close interactions with the SMC are primarily responsible for the asymmetric stellar
structures seen in the periphery of the LMC. The orientation and density of these arcs can be used to
constrain the LMC’s interaction history with and impact parameter of the SMC. More generally, we
find that such asymmetric structures should be ubiquitous about pairs of dwarfs and can persist for
1-2 Gyr even after the secondary merges entirely with the primary. As such, the lack of a companion
around a Magellanic Irregular does not disprove the hypothesis that their asymmetric structures are
driven by dwarf-dwarf interactions.
Proper-motion age dating of the progeny of Nova Scorpii ad 1437Sérgio Sacani
‘Cataclysmic variables’ are binary star systems in which one
star of the pair is a white dwarf, and which often generate bright
and energetic stellar outbursts. Classical novae are one type of
outburst: when the white dwarf accretes enough matter from its
companion, the resulting hydrogen-rich atmospheric envelope
can host a runaway thermonuclear reaction that generates a rapid
brightening1–4. Achieving peak luminosities of up to one million
times that of the Sun5
, all classical novae are recurrent, on timescales
of months6
to millennia7
. During the century before and after an
eruption, the ‘novalike’ binary systems that give rise to classical
novae exhibit high rates of mass transfer to their white dwarfs8
.
Another type of outburst is the dwarf nova: these occur in binaries
that have stellar masses and periods indistinguishable from those
of novalikes9
but much lower mass-transfer rates10, when accretiondisk
instabilities11 drop matter onto the white dwarfs. The coexistence
at the same orbital period of novalike binaries and dwarf
novae—which are identical but for their widely varying accretion
rates—has been a longstanding puzzle9
. Here we report the recovery
of the binary star underlying the classical nova eruption of 11 March
ad 1437 (refs 12, 13), and independently confirm its age by propermotion
dating. We show that, almost 500 years after a classical-nova
event, the system exhibited dwarf-nova eruptions. The three other
oldest recovered classical novae14–16 display nova shells, but lack
firm post-eruption ages17,18, and are also dwarf novae at present.
We conclude that many old novae become dwarf novae for part of
the millennia between successive nova eruptions19,
A 2 4_determination_of_the_local_value_of_the_hubble_constantSérgio Sacani
We use the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST) to
reduce the uncertainty in the local value of the Hubble constant from 3.3% to 2.4%.
The bulk of this improvement comes from new, near-infrared observations of Cepheid
variables in 11 host galaxies of recent type Ia supernovae (SNe Ia), more than doubling
the sample of reliable SNe Ia having a Cepheid-calibrated distance to a total of 19; these
in turn leverage the magnitude-redshift relation based on 300 SNe Ia at z <0.15. All
19 hosts as well as the megamaser system NGC4258 have been observed with WFC3
in the optical and near-infrared, thus nullifying cross-instrument zeropoint errors in the
relative distance estimates from Cepheids. Other noteworthy improvements include a
33% reduction in the systematic uncertainty in the maser distance to NGC4258, a larger
sample of Cepheids in the Large Magellanic Cloud (LMC), a more robust distance to
the LMC based on late-type detached eclipsing binaries (DEBs), HST observations of
Cepheids in M31, and new HST-based trigonometric parallaxes for Milky Way (MW)
Cepheids.
A estrela KIC 8462852 voltou a ser comentada na mídia astronômica essa semana, e vamos entender porque. Mas antes uma pequena recordação.
Provavelmente, você já ouviu falar da estrela KIC 8462852, que recebeu o nome carinhoso de Estrela de Tabby, em homenagem a Tabetha Boyajian que liderou a equipe que descobriu o seu estranho comportamento. Essa foi a estrela que chamou muito a atenção da imprensa no final do último ano. Os astrônomos utilizaram observações feitas com o Kepler e mediram as variações no brilho da estrela. Algumas dessas variações eram significativas, com uma queda de brilho de cerca de 20%.
Isso é muito. Não poderia ser um planeta passando em frente a estrela, pois as quedas dos brilhos também não eram periódicas, e a quantidade de luz bloqueada era diferente a cada vez. Além disso, até um planeta do tamanho de Júpiter, bloqueia menos de 1% da luz da estrela.
No artigo original, Boyajian e sua equipe discutiu uma série de hipóteses e possíveis cenários que poderiam causar a queda de brilho, eliminando algumas delas e levantando outras. Entre as hipóteses, aquela que ganhou uma força foi a de uma família de cometas passando na frente da estrela, com alguns deles colidindo entre si e gerando uma nuvem espessa que poderia bloquear a luz da estrela.
DISCOVERY OF A GALAXY CLUSTER WITH A VIOLENTLY STARBURSTING CORE AT z = 2:506Sérgio Sacani
We report the discovery of a remarkable concentration of massive galaxies with extended X-ray
emission at zspec = 2:506, which contains 11 massive (M & 1011M) galaxies in the central 80kpc
region (11.6 overdensity). We have spectroscopically conrmed 17 member galaxies with 11 from CO
and the remaining ones from H. The X-ray luminosity, stellar mass content and velocity dispersion
all point to a collapsed, cluster-sized dark matter halo with mass M200c = 1013:90:2M, making it
the most distant X-ray-detected cluster known to date. Unlike other clusters discovered so far, this
structure is dominated by star-forming galaxies (SFGs) in the core with only 2 out of the 11 massive
galaxies classied as quiescent. The star formation rate (SFR) in the 80kpc core reaches 3400 M
yr 1 with a gas depletion time of 200 Myr, suggesting that we caught this cluster in rapid build-up
of a dense core. The high SFR is driven by both a high abundance of SFGs and a higher starburst
fraction ( 25%, compared to 3%-5% in the eld). The presence of both a collapsed, cluster-sized
halo and a predominant population of massive SFGs suggests that this structure could represent an
important transition phase between protoclusters and mature clusters. It provides evidence that the
main phase of massive galaxy passivization will take place after galaxies accrete onto the cluster,
providing new insights into massive cluster formation at early epochs. The large integrated stellar
mass at such high redshift challenges our understanding of massive cluster formation.
The completeness-corrected rate of stellar encounters with the Sun from the f...Sérgio Sacani
I report on close encounters of stars to the Sun found in the first Gaia data release (GDR1). Combining Gaia astrometry with radial
velocities of around 320 000 stars drawn from various catalogues, I integrate orbits in a Galactic potential to identify those stars which
come within a few parsecs. Such encounters could influence the solar system, for example through gravitational perturbations of the
Oort cloud. 16 stars are found to come within 2 pc (although a few of these have dubious data). This is fewer than were found in a
similar study based on Hipparcos data, even though the present study has many more candidates. This is partly because I reject stars
with large radial velocity uncertainties (>10 km s−1
), and partly because of missing stars in GDR1 (especially at the bright end). The
closest encounter found is Gl 710, a K dwarf long-known to come close to the Sun in about 1.3 Myr. The Gaia astrometry predict
a much closer passage than pre-Gaia estimates, however: just 16 000 AU (90% confidence interval: 10 000–21 000 AU), which will
bring this star well within the Oort cloud. Using a simple model for the spatial, velocity, and luminosity distributions of stars, together
with an approximation of the observational selection function, I model the incompleteness of this Gaia-based search as a function
of the time and distance of closest approach. Applying this to a subset of the observed encounters (excluding duplicates and stars
with implausibly large velocities), I estimate the rate of stellar encounters within 5 pc averaged over the past and future 5 Myr to be
545±59 Myr−1
. Assuming a quadratic scaling of the rate within some encounter distance (which my model predicts), this corresponds
to 87 ± 9 Myr−1 within 2 pc. A more accurate analysis and assessment will be possible with future Gaia data releases.
The 19 Feb. 2016 Outburst of Comet 67P/CG: An ESA Rosetta Multi-Instrument StudySérgio Sacani
On 19 Feb. 2016 nine Rosetta instruments serendipitously observed an outburst of gas and dust
from the nucleus of comet 67P/Churyumov-Gerasimenko. Among these instruments were cameras
and spectrometers ranging from UV over visible to microwave wavelengths, in-situ gas, dust and
plasma instruments, and one dust collector. At 9:40 a dust cloud developed at the edge of an image
in the shadowed region of the nucleus. Over the next two hours the instruments recorded a signature
of the outburst that signicantly exceeded the background. The enhancement ranged from 50% of
the neutral gas density at Rosetta to factors >100 of the brightness of the coma near the nucleus.
Dust related phenomena (dust counts or brightness due to illuminated dust) showed the strongest
enhancements (factors >10). However, even the electron density at Rosetta increased by a factor 3
and consequently the spacecraft potential changed from 16V to 20V during the outburst. A
clear sequence of events was observed at the distance of Rosetta (34 km from the nucleus): within 15
minutes the Star Tracker camera detected fast particles ( 25 ms 1) while 100 m radius particles
were detected by the GIADA dust instrument 1 hour later at a speed of 6 ms 1. The slowest
were individual mm to cm sized grains observed by the OSIRIS cameras. Although the outburst
originated just outside the FOV of the instruments, the source region and the magnitude of the
outburst could be determined.
Is there an_exoplanet_in_the_solar_systemSérgio Sacani
We investigate the prospects for the capture of the proposed Planet 9 from other
stars in the Sun’s birth cluster. Any capture scenario must satisfy three conditions:
the encounter must be more distant than ∼ 150 au to avoid perturbing the Kuiper
belt; the other star must have a wide-orbit planet (a & 100 au); the planet must be
captured onto an appropriate orbit to sculpt the orbital distribution of wide-orbit
Solar System bodies. Here we use N-body simulations to show that these criteria may
be simultaneously satisfied. In a few percent of slow close encounters in a cluster,
bodies are captured onto heliocentric, Planet 9-like orbits. During the ∼ 100 Myr
cluster phase, many stars are likely to host planets on highly-eccentric orbits with
apastron distances beyond 100 au if Neptune-sized planets are common and susceptible
to planet–planet scattering. While the existence of Planet 9 remains unproven, we
consider capture from one of the Sun’s young brethren a plausible route to explain such
an object’s orbit. Capture appears to predict a large population of Trans-Neptunian
Objects (TNOs) whose orbits are aligned with the captured planet, and we propose
that different formation mechanisms will be distinguishable based on their imprint on
the distribution of TNOs
High-resolution UV/Optical/IR Imaging of Jupiter in 2016–2019Sérgio Sacani
Imaging observations of Jupiter with high spatial resolution were acquired beginning in 2016, with a cadence of 53
days to coincide with atmospheric observations of the Juno spacecraft during each perijove pass. The Wide Field
Camera 3 (WFC3) aboard the Hubble Space Telescope (HST) collected Jupiter images from 236 to 925 nm in 14
filters. The Near-Infrared Imager (NIRI) at Gemini North imaged Jovian thermal emission using a lucky-imaging
approach (co-adding the sharpest frames taken from a sequence of short exposures), using the M′ filter at 4.7 μm.
We discuss the data acquisition and processing and an archive collection that contains the processed WFC3 and
NIRI data (doi:10.17909/T94T1H). Zonal winds remain steady over time at most latitudes, but significant
evolution of the wind profile near 24°N in 2016 and near 15°S in 2017 was linked with convective superstorm
eruptions. Persistent mesoscale waves were seen throughout the 2016–2019 period. We link groups of lightning
flashes observed by the Juno team with water clouds in a large convective plume near 15°S and in cyclones near
35°N–55°N. Thermal infrared maps at the 10.8 micron wavelength obtained at the Very Large Telescope show
consistent high brightness temperature anomalies, despite a diversity of aerosol properties seen in the HST data.
Both WFC3 and NIRI imaging reveal depleted aerosols consistent with downwelling around the periphery of the
15°S storm, which was also observed by the Atacama Large Millimeter/submillimeter Array. NIRI imaging of
the Great Red Spot shows that locally reduced cloud opacity is responsible for dark features within the vortex. The
HST data maps multiple concentric polar hoods of high-latitude hazes.
T he effect_of_orbital_configuration)_on_the_possible_climates_and_habitabili...Sérgio Sacani
As lower-mass stars often host multiple rocky planets, gravitational interactions among planets can have significant
effects on climate and habitability over long timescales. Here we explore a specific case, Kepler-62f (Borucki et al.,
2013), a potentially habitable planet in a five-planet system with a K2V host star. N-body integrations reveal the
stable range of initial eccentricities for Kepler-62f is 0.00 £ e £ 0.32, absent the effect of additional, undetected
planets. We simulate the tidal evolution of Kepler-62f in this range and find that, for certain assumptions, the planet
can be locked in a synchronous rotation state. Simulations using the 3-D Laboratoire de Me´te´orologie Dynamique
(LMD) Generic global climate model (GCM) indicate that the surface habitability of this planet is sensitive to
orbital configuration.With 3 bar of CO2 in its atmosphere, we find that Kepler-62f would only be warm enough for
surface liquid water at the upper limit of this eccentricity range, providing it has a high planetary obliquity
(between 60 and 90). A climate similar to that of modern-day Earth is possible for the entire range of stable
eccentricities if atmospheric CO2 is increased to 5 bar levels. In a low-CO2 case (Earth-like levels), simulations
with version 4 of the Community Climate System Model (CCSM4) GCM and LMD Generic GCM indicate that
increases in planetary obliquity and orbital eccentricity coupled with an orbital configuration that places the
summer solstice at or near pericenter permit regions of the planet with above-freezing surface temperatures. This
may melt ice sheets formed during colder seasons. If Kepler-62f is synchronously rotating and has an ocean, CO2
levels above 3 bar would be required to distribute enough heat to the nightside of the planet to avoid atmospheric
freeze-out and permit a large enough region of open water at the planet’s substellar point to remain stable. Overall,
we find multiple plausible combinations of orbital and atmospheric properties that permit surface liquid water on
Kepler-62f. Key Words: Extrasolar planets—Habitability—Planetary environments. Astrobiology 16, xxx–xxx.
This are few simple slides those are just showing some idea and this ideas can make you think something greater.
All we have lot's of unused clothes at our home and by using those we can make something different, something useful and creative..
just need a little passion to make some extraordinary things.
And this slides are just for make you think, what else you can create actually..
The canarias einstein_ring_a_newly_discovered_optical_einstein_ringSérgio Sacani
We report the discovery of an optical Einstein Ring in the Sculptor constellation,
IAC J010127-334319, in the vicinity of the Sculptor Dwarf Spheroidal Galaxy. It is
an almost complete ring ( 300◦) with a diameter of 4.5 arcsec. The discovery was
made serendipitously from inspecting Dark Energy Camera (DECam) archive imaging
data. Confirmation of the object nature has been obtained by deriving spectroscopic
redshifts for both components, lens and source, from observations at the 10.4 m Gran
Telescopio CANARIAS (GTC) with the spectrograph OSIRIS. The lens, a massive
early-type galaxy, has a redshift of z = 0.581 while the source is a starburst galaxy
with redshift of z = 1.165. The total enclosed mass that produces the lensing effect
has been estimated to be Mtot = (1.86 ± 0.23) · 1012M⊙.
We present deep optical images of the Large and Small Magellanic Clouds (LMC and SMC) using
a low cost telephoto lens with a wide field of view to explore stellar substructure in the outskirts
of the stellar disk of the LMC (r < 10 degrees from the center). These data have higher resolution
than existing star count maps, and highlight the existence of stellar arcs and multiple spiral arms in
the northern periphery, with no comparable counterparts in the South. We compare these data to
detailed simulations of the LMC disk outskirts, following interactions with its low mass companion,
the SMC. We consider interaction in isolation and with the inclusion of the Milky Way tidal field.
The simulations are used to assess the origin of the northern structures, including also the low density
stellar arc recently identified in the DES data by Mackey et al. (2015) at ∼ 15 degrees. We conclude
that repeated close interactions with the SMC are primarily responsible for the asymmetric stellar
structures seen in the periphery of the LMC. The orientation and density of these arcs can be used to
constrain the LMC’s interaction history with and impact parameter of the SMC. More generally, we
find that such asymmetric structures should be ubiquitous about pairs of dwarfs and can persist for
1-2 Gyr even after the secondary merges entirely with the primary. As such, the lack of a companion
around a Magellanic Irregular does not disprove the hypothesis that their asymmetric structures are
driven by dwarf-dwarf interactions.
Proper-motion age dating of the progeny of Nova Scorpii ad 1437Sérgio Sacani
‘Cataclysmic variables’ are binary star systems in which one
star of the pair is a white dwarf, and which often generate bright
and energetic stellar outbursts. Classical novae are one type of
outburst: when the white dwarf accretes enough matter from its
companion, the resulting hydrogen-rich atmospheric envelope
can host a runaway thermonuclear reaction that generates a rapid
brightening1–4. Achieving peak luminosities of up to one million
times that of the Sun5
, all classical novae are recurrent, on timescales
of months6
to millennia7
. During the century before and after an
eruption, the ‘novalike’ binary systems that give rise to classical
novae exhibit high rates of mass transfer to their white dwarfs8
.
Another type of outburst is the dwarf nova: these occur in binaries
that have stellar masses and periods indistinguishable from those
of novalikes9
but much lower mass-transfer rates10, when accretiondisk
instabilities11 drop matter onto the white dwarfs. The coexistence
at the same orbital period of novalike binaries and dwarf
novae—which are identical but for their widely varying accretion
rates—has been a longstanding puzzle9
. Here we report the recovery
of the binary star underlying the classical nova eruption of 11 March
ad 1437 (refs 12, 13), and independently confirm its age by propermotion
dating. We show that, almost 500 years after a classical-nova
event, the system exhibited dwarf-nova eruptions. The three other
oldest recovered classical novae14–16 display nova shells, but lack
firm post-eruption ages17,18, and are also dwarf novae at present.
We conclude that many old novae become dwarf novae for part of
the millennia between successive nova eruptions19,
A 2 4_determination_of_the_local_value_of_the_hubble_constantSérgio Sacani
We use the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST) to
reduce the uncertainty in the local value of the Hubble constant from 3.3% to 2.4%.
The bulk of this improvement comes from new, near-infrared observations of Cepheid
variables in 11 host galaxies of recent type Ia supernovae (SNe Ia), more than doubling
the sample of reliable SNe Ia having a Cepheid-calibrated distance to a total of 19; these
in turn leverage the magnitude-redshift relation based on 300 SNe Ia at z <0.15. All
19 hosts as well as the megamaser system NGC4258 have been observed with WFC3
in the optical and near-infrared, thus nullifying cross-instrument zeropoint errors in the
relative distance estimates from Cepheids. Other noteworthy improvements include a
33% reduction in the systematic uncertainty in the maser distance to NGC4258, a larger
sample of Cepheids in the Large Magellanic Cloud (LMC), a more robust distance to
the LMC based on late-type detached eclipsing binaries (DEBs), HST observations of
Cepheids in M31, and new HST-based trigonometric parallaxes for Milky Way (MW)
Cepheids.
A estrela KIC 8462852 voltou a ser comentada na mídia astronômica essa semana, e vamos entender porque. Mas antes uma pequena recordação.
Provavelmente, você já ouviu falar da estrela KIC 8462852, que recebeu o nome carinhoso de Estrela de Tabby, em homenagem a Tabetha Boyajian que liderou a equipe que descobriu o seu estranho comportamento. Essa foi a estrela que chamou muito a atenção da imprensa no final do último ano. Os astrônomos utilizaram observações feitas com o Kepler e mediram as variações no brilho da estrela. Algumas dessas variações eram significativas, com uma queda de brilho de cerca de 20%.
Isso é muito. Não poderia ser um planeta passando em frente a estrela, pois as quedas dos brilhos também não eram periódicas, e a quantidade de luz bloqueada era diferente a cada vez. Além disso, até um planeta do tamanho de Júpiter, bloqueia menos de 1% da luz da estrela.
No artigo original, Boyajian e sua equipe discutiu uma série de hipóteses e possíveis cenários que poderiam causar a queda de brilho, eliminando algumas delas e levantando outras. Entre as hipóteses, aquela que ganhou uma força foi a de uma família de cometas passando na frente da estrela, com alguns deles colidindo entre si e gerando uma nuvem espessa que poderia bloquear a luz da estrela.
DISCOVERY OF A GALAXY CLUSTER WITH A VIOLENTLY STARBURSTING CORE AT z = 2:506Sérgio Sacani
We report the discovery of a remarkable concentration of massive galaxies with extended X-ray
emission at zspec = 2:506, which contains 11 massive (M & 1011M) galaxies in the central 80kpc
region (11.6 overdensity). We have spectroscopically conrmed 17 member galaxies with 11 from CO
and the remaining ones from H. The X-ray luminosity, stellar mass content and velocity dispersion
all point to a collapsed, cluster-sized dark matter halo with mass M200c = 1013:90:2M, making it
the most distant X-ray-detected cluster known to date. Unlike other clusters discovered so far, this
structure is dominated by star-forming galaxies (SFGs) in the core with only 2 out of the 11 massive
galaxies classied as quiescent. The star formation rate (SFR) in the 80kpc core reaches 3400 M
yr 1 with a gas depletion time of 200 Myr, suggesting that we caught this cluster in rapid build-up
of a dense core. The high SFR is driven by both a high abundance of SFGs and a higher starburst
fraction ( 25%, compared to 3%-5% in the eld). The presence of both a collapsed, cluster-sized
halo and a predominant population of massive SFGs suggests that this structure could represent an
important transition phase between protoclusters and mature clusters. It provides evidence that the
main phase of massive galaxy passivization will take place after galaxies accrete onto the cluster,
providing new insights into massive cluster formation at early epochs. The large integrated stellar
mass at such high redshift challenges our understanding of massive cluster formation.
The completeness-corrected rate of stellar encounters with the Sun from the f...Sérgio Sacani
I report on close encounters of stars to the Sun found in the first Gaia data release (GDR1). Combining Gaia astrometry with radial
velocities of around 320 000 stars drawn from various catalogues, I integrate orbits in a Galactic potential to identify those stars which
come within a few parsecs. Such encounters could influence the solar system, for example through gravitational perturbations of the
Oort cloud. 16 stars are found to come within 2 pc (although a few of these have dubious data). This is fewer than were found in a
similar study based on Hipparcos data, even though the present study has many more candidates. This is partly because I reject stars
with large radial velocity uncertainties (>10 km s−1
), and partly because of missing stars in GDR1 (especially at the bright end). The
closest encounter found is Gl 710, a K dwarf long-known to come close to the Sun in about 1.3 Myr. The Gaia astrometry predict
a much closer passage than pre-Gaia estimates, however: just 16 000 AU (90% confidence interval: 10 000–21 000 AU), which will
bring this star well within the Oort cloud. Using a simple model for the spatial, velocity, and luminosity distributions of stars, together
with an approximation of the observational selection function, I model the incompleteness of this Gaia-based search as a function
of the time and distance of closest approach. Applying this to a subset of the observed encounters (excluding duplicates and stars
with implausibly large velocities), I estimate the rate of stellar encounters within 5 pc averaged over the past and future 5 Myr to be
545±59 Myr−1
. Assuming a quadratic scaling of the rate within some encounter distance (which my model predicts), this corresponds
to 87 ± 9 Myr−1 within 2 pc. A more accurate analysis and assessment will be possible with future Gaia data releases.
The 19 Feb. 2016 Outburst of Comet 67P/CG: An ESA Rosetta Multi-Instrument StudySérgio Sacani
On 19 Feb. 2016 nine Rosetta instruments serendipitously observed an outburst of gas and dust
from the nucleus of comet 67P/Churyumov-Gerasimenko. Among these instruments were cameras
and spectrometers ranging from UV over visible to microwave wavelengths, in-situ gas, dust and
plasma instruments, and one dust collector. At 9:40 a dust cloud developed at the edge of an image
in the shadowed region of the nucleus. Over the next two hours the instruments recorded a signature
of the outburst that signicantly exceeded the background. The enhancement ranged from 50% of
the neutral gas density at Rosetta to factors >100 of the brightness of the coma near the nucleus.
Dust related phenomena (dust counts or brightness due to illuminated dust) showed the strongest
enhancements (factors >10). However, even the electron density at Rosetta increased by a factor 3
and consequently the spacecraft potential changed from 16V to 20V during the outburst. A
clear sequence of events was observed at the distance of Rosetta (34 km from the nucleus): within 15
minutes the Star Tracker camera detected fast particles ( 25 ms 1) while 100 m radius particles
were detected by the GIADA dust instrument 1 hour later at a speed of 6 ms 1. The slowest
were individual mm to cm sized grains observed by the OSIRIS cameras. Although the outburst
originated just outside the FOV of the instruments, the source region and the magnitude of the
outburst could be determined.
Is there an_exoplanet_in_the_solar_systemSérgio Sacani
We investigate the prospects for the capture of the proposed Planet 9 from other
stars in the Sun’s birth cluster. Any capture scenario must satisfy three conditions:
the encounter must be more distant than ∼ 150 au to avoid perturbing the Kuiper
belt; the other star must have a wide-orbit planet (a & 100 au); the planet must be
captured onto an appropriate orbit to sculpt the orbital distribution of wide-orbit
Solar System bodies. Here we use N-body simulations to show that these criteria may
be simultaneously satisfied. In a few percent of slow close encounters in a cluster,
bodies are captured onto heliocentric, Planet 9-like orbits. During the ∼ 100 Myr
cluster phase, many stars are likely to host planets on highly-eccentric orbits with
apastron distances beyond 100 au if Neptune-sized planets are common and susceptible
to planet–planet scattering. While the existence of Planet 9 remains unproven, we
consider capture from one of the Sun’s young brethren a plausible route to explain such
an object’s orbit. Capture appears to predict a large population of Trans-Neptunian
Objects (TNOs) whose orbits are aligned with the captured planet, and we propose
that different formation mechanisms will be distinguishable based on their imprint on
the distribution of TNOs
High-resolution UV/Optical/IR Imaging of Jupiter in 2016–2019Sérgio Sacani
Imaging observations of Jupiter with high spatial resolution were acquired beginning in 2016, with a cadence of 53
days to coincide with atmospheric observations of the Juno spacecraft during each perijove pass. The Wide Field
Camera 3 (WFC3) aboard the Hubble Space Telescope (HST) collected Jupiter images from 236 to 925 nm in 14
filters. The Near-Infrared Imager (NIRI) at Gemini North imaged Jovian thermal emission using a lucky-imaging
approach (co-adding the sharpest frames taken from a sequence of short exposures), using the M′ filter at 4.7 μm.
We discuss the data acquisition and processing and an archive collection that contains the processed WFC3 and
NIRI data (doi:10.17909/T94T1H). Zonal winds remain steady over time at most latitudes, but significant
evolution of the wind profile near 24°N in 2016 and near 15°S in 2017 was linked with convective superstorm
eruptions. Persistent mesoscale waves were seen throughout the 2016–2019 period. We link groups of lightning
flashes observed by the Juno team with water clouds in a large convective plume near 15°S and in cyclones near
35°N–55°N. Thermal infrared maps at the 10.8 micron wavelength obtained at the Very Large Telescope show
consistent high brightness temperature anomalies, despite a diversity of aerosol properties seen in the HST data.
Both WFC3 and NIRI imaging reveal depleted aerosols consistent with downwelling around the periphery of the
15°S storm, which was also observed by the Atacama Large Millimeter/submillimeter Array. NIRI imaging of
the Great Red Spot shows that locally reduced cloud opacity is responsible for dark features within the vortex. The
HST data maps multiple concentric polar hoods of high-latitude hazes.
T he effect_of_orbital_configuration)_on_the_possible_climates_and_habitabili...Sérgio Sacani
As lower-mass stars often host multiple rocky planets, gravitational interactions among planets can have significant
effects on climate and habitability over long timescales. Here we explore a specific case, Kepler-62f (Borucki et al.,
2013), a potentially habitable planet in a five-planet system with a K2V host star. N-body integrations reveal the
stable range of initial eccentricities for Kepler-62f is 0.00 £ e £ 0.32, absent the effect of additional, undetected
planets. We simulate the tidal evolution of Kepler-62f in this range and find that, for certain assumptions, the planet
can be locked in a synchronous rotation state. Simulations using the 3-D Laboratoire de Me´te´orologie Dynamique
(LMD) Generic global climate model (GCM) indicate that the surface habitability of this planet is sensitive to
orbital configuration.With 3 bar of CO2 in its atmosphere, we find that Kepler-62f would only be warm enough for
surface liquid water at the upper limit of this eccentricity range, providing it has a high planetary obliquity
(between 60 and 90). A climate similar to that of modern-day Earth is possible for the entire range of stable
eccentricities if atmospheric CO2 is increased to 5 bar levels. In a low-CO2 case (Earth-like levels), simulations
with version 4 of the Community Climate System Model (CCSM4) GCM and LMD Generic GCM indicate that
increases in planetary obliquity and orbital eccentricity coupled with an orbital configuration that places the
summer solstice at or near pericenter permit regions of the planet with above-freezing surface temperatures. This
may melt ice sheets formed during colder seasons. If Kepler-62f is synchronously rotating and has an ocean, CO2
levels above 3 bar would be required to distribute enough heat to the nightside of the planet to avoid atmospheric
freeze-out and permit a large enough region of open water at the planet’s substellar point to remain stable. Overall,
we find multiple plausible combinations of orbital and atmospheric properties that permit surface liquid water on
Kepler-62f. Key Words: Extrasolar planets—Habitability—Planetary environments. Astrobiology 16, xxx–xxx.
This are few simple slides those are just showing some idea and this ideas can make you think something greater.
All we have lot's of unused clothes at our home and by using those we can make something different, something useful and creative..
just need a little passion to make some extraordinary things.
And this slides are just for make you think, what else you can create actually..
Resolved gas cavities_in_transitional_disks_inferred_from_co_isotopologs_with...Sérgio Sacani
Com o auxílio do Atacama Large Millimeter/submillimeter Array (ALMA), astrônomos obtiveram as mais claras indicações conseguidas até hoje de que planetas com várias vezes a massa de Júpiter se formaram recentemente nos discos de gás e poeira que rodeiam quatro estrelas jovens. Medições do gás em torno das estrelas forneceram também pistas adicionais relativas às propriedades destes planetas.
Existem planetas em órbita de quase todas as estrelas, no entanto os astrônomos ainda não compreendem bem como — e sob que condições — é que estes corpos se formam. Para responder a estas perguntas, foi feito um estudo dos discos em rotação de gás e poeira que se situam em torno de estrelas jovens e a partir dos quais se formam os planetas. Como estes discos são pequenos e encontram-se muito distantes da Terra, foi necessário utilizar o ALMA para revelar os seus segredos.
Uma classe especial destes discos, os discos transitórios, possui uma falta surpreendente de poeira nos seus centros, na região em torno da estrela. Duas ideias principais foram adiantadas para explicar estas estranhas cavidades na poeira dos discos. A primeira diz que ventos estelares fortes e radiação intensa poderiam ter soprado para longe ou mesmo destruído o material à sua volta [1]. Alternativamente, planetas jovens massivos em processo de formação poderão também ter limpo o material à medida que orbitam a estrela [2].
Con la presencia de mujeres de pueblos originarios de toda la República, el secretario de Gobernación, Miguel Ángel Osorio Chong, acompañado por el gobernador Manuel Velasco Coello y la directora general de la Comisión Nacional para el Desarrollo de los Pueblos Indígenas
Blockchain en vertrouwensdiensten, Digitaal Zakendoen, Bunnik, June 16th 2016Pascal Van Hecke
Presentation in Dutch on what Blockchain (and smart contracts) can do in the context of trust services (e.g. online authentication, attestation, notarising...)
Event link: http://digitaal-zakendoen.weebly.com/7-vertrouwensdiensten.html
XUE: Molecular Inventory in the Inner Region of an Extremely Irradiated Proto...Sérgio Sacani
We present the first results of the eXtreme UV Environments (XUE) James Webb Space Telescope (JWST)
program, which focuses on the characterization of planet-forming disks in massive star-forming regions. These
regions are likely representative of the environment in which most planetary systems formed. Understanding the
impact of environment on planet formation is critical in order to gain insights into the diversity of the observed
exoplanet populations. XUE targets 15 disks in three areas of NGC 6357, which hosts numerous massive OB stars,
including some of the most massive stars in our Galaxy. Thanks to JWST, we can, for the first time, study the effect
of external irradiation on the inner (<10 au), terrestrial-planet-forming regions of protoplanetary disks. In this study,
we report on the detection of abundant water, CO, 12CO2, HCN, and C2H2 in the inner few au of XUE 1, a highly
irradiated disk in NGC 6357. In addition, small, partially crystalline silicate dust is present at the disk surface. The
derived column densities, the oxygen-dominated gas-phase chemistry, and the presence of silicate dust are
surprisingly similar to those found in inner disks located in nearby, relatively isolated low-mass star-forming
regions. Our findings imply that the inner regions of highly irradiated disks can retain similar physical and chemical
conditions to disks in low-mass star-forming regions, thus broadening the range of environments with similar
conditions for inner disk rocky planet formation to the most extreme star-forming regions in our Galaxy.
The Variable Detection of Atmospheric Escape around the Young, Hot Neptune AU...Sérgio Sacani
Photoevaporation is a potential explanation for several features within exoplanet demographics. Atmospheric escape
observed in young Neptune-sized exoplanets can provide insight into and characterize which mechanisms drive this
evolution and at what times they dominate. AU Mic b is one such exoplanet, slightly larger than Neptune (4.19 R⊕).
It closely orbits a 23 Myr pre-main-sequence M dwarf with an orbital period of 8.46 days. We obtained two visits of
AU Mic b at Lyα with Hubble Space Telescope (HST)/Space Telescope Imaging Spectrograph. One flare within the
first HST visit is characterized and removed from our search for a planetary transit. We present a nondetection in our
first visit, followed by the detection of escaping neutral hydrogen ahead of the planet in our second visit. The outflow
absorbed ∼30% of the star’s Lyα blue wing 2.5 hr before the planet’s white-light transit. We estimate that the
highest-velocity escaping material has a column density of 1013.96 cm−2 and is moving 61.26 km s−1 away from the
host star. AU Mic b’s large high-energy irradiation could photoionize its escaping neutral hydrogen in 44 minutes,
rendering it temporarily unobservable. Our time-variable Lyα transit ahead of AU Mic b could also be explained by
an intermediate stellar wind strength from AU Mic that shapes the escaping material into a leading tail. Future Lyα
observations of this system will confirm and characterize the unique variable nature of its Lyα transit, which,
combined with modeling, will tune the importance of stellar wind and photoionization.
We present the 2020 version of the Siena Galaxy Atlas (SGA-2020), a multiwavelength optical and infrared
imaging atlas of 383,620 nearby galaxies. The SGA-2020 uses optical grz imaging over ≈20,000 deg2 from the
Dark Energy Spectroscopic Instrument (DESI) Legacy Imaging Surveys Data Release 9 and infrared imaging in
four bands (spanning 3.4–22 μm) from the 6 year unWISE coadds; it is more than 95% complete for galaxies larger
than R(26) ≈ 25″ and r < 18 measured at the 26 mag arcsec−2 isophote in the r band. The atlas delivers precise
coordinates, multiwavelength mosaics, azimuthally averaged optical surface-brightness profiles, model images and
photometry, and additional ancillary metadata for the full sample. Coupled with existing and forthcoming optical
spectroscopy from the DESI, the SGA-2020 will facilitate new detailed studies of the star formation and mass
assembly histories of nearby galaxies; enable precise measurements of the local velocity field via the Tully–Fisher
and fundamental plane relations; serve as a reference sample of lasting legacy value for time-domain and
multimessenger astronomical events; and more.
Uma equipe formada por astrônomos de Israel, da Europa, da Coreia e dos EUA, anunciou a descoberta de um exoplaneta gigante gasoso circumbinário, na zona habitável de seu par de estrelas, uma ocorrência surpreendentemente comum para os exoplanetas circumbinários descobertos pela missão Kepler/K2 da NASA.
Lembrando o planeta da ficção, Tatooine, exoplanetas circumbinários orbitam duas estrelas e assim têm dois sóis em seu céu.
O exoplaneta circumbinário, recém-descoberto, denominado de Kepler-453b, leva 240.5 dias para orbitar suas estrelas, enquanto as estrelas orbitam uma com relação a outra a cada 27.3 dias.
A estrela maior, a Kepler-453A, é similar ao nosso Sol, contendo 94% da massa do Sol, enquanto que a estrela menor, a Kepler-453B, tem cerca de 20% da massa e é mais fria e mais apagada.
O sistema binário, localiza-se na constelação de Lyra, e está a aproximadamente 1400 anos-luz de distância da Terra. Estima-se que esse sistema tenha entre 1 e 2 bilhões de anos de vida, sendo bem mais novo que o nosso Sistema Solar.
Também conhecido como KIC 9632895b, o Kepler-453b tem um raio 6.2 vezes maior que o da Terra. Sua massa não foi medida nos dados atuais, mas provavelmente ele deve ter cerca de 16 vezes a massa da Terra.
De acordo com os astrônomos, o Kepler-453b, é o terceiro planeta circumbinário da missão Kepler, descoberto na zona habitável de um par de estrelas.
Devido ao seu tamanho, e a sua natureza gasosa, o planeta pouco provavelmente deve abrigar a vida como nós a conhecemos. Contudo, ele pode, como os gigantes gasosos do Sistema Solar, ter grandes luas, e essas luas poderiam ser habitáveis. Sua órbita se manterá estável por 10 milhões de anos, aumentando a possibilidade da vida se formar nas suas luas.
Com o número de exoplanetas circumbinários conhecidos agora em dez, os cientistas podem começar a comparar diferentes sistemas e procurar uma tendência. Os sistemas tendem a ser bem compactos e podem aparecer num grande número de configurações.
Uma vez pensados como sendo raros e até mesmo impossíveis de existir, essa e outras descobertas do Kepler, confirmam que esses planetas são comuns na nossa Via Láctea.
“A diversidade e complexidade desses sistemas circumbinários é algo maravilhoso. Cada novo planeta circumbinário, é uma joia, revelando algo inesperado e desafiador”, disse o Prof. William Welsh da Universidade Estadual de San Diego, e o primeiro autor do artigo que descreve a descoberta, publicado no Astrophysical Journal.
Fonte:
http://www.sci-news.com/astronomy/science-kepler453b-circumbinary-exoplanet-03117.html
The Possible Tidal Demise of Kepler’s First Planetary SystemSérgio Sacani
We present evidence of tidally-driven inspiral in the Kepler-1658 (KOI-4) system, which consists of a giant planet
(1.1RJ, 5.9MJ) orbiting an evolved host star (2.9Re, 1.5Me). Using transit timing measurements from Kepler,
Palomar/WIRC, and TESS, we show that the orbital period of Kepler-1658b appears to be decreasing at a rate = -
+ P 131 22
20 ms yr−1
, corresponding to an infall timescale P P » 2.5 Myr. We consider other explanations for the
data including line-of-sight acceleration and orbital precession, but find them to be implausible. The observed
period derivative implies a tidal quality factor
¢ = ´ -
+ Q 2.50 10 0.62
0.85 4, in good agreement with theoretical
predictions for inertial wave dissipation in subgiant stars. Additionally, while it probably cannot explain the entire
inspiral rate, a small amount of planetary dissipation could naturally explain the deep optical eclipse observed for
the planet via enhanced thermal emission. As the first evolved system with detected inspiral, Kepler-1658 is a new
benchmark for understanding tidal physics at the end of the planetary life cycle
The pristine nature of SMSS 1605−1443 revealed by ESPRESSOSérgio Sacani
SMSS J160540.18−144323.1 is the carbon-enhanced metal-poor (CEMP) star with the lowest iron abundance ever measured, [Fe/H] =
−6.2, which was first reported with the SkyMapper telescope. The carbon abundance is A(C) ≈ 6.1 in the low-C band, as the majority of the stars
in this metallicity range. Yet, constraining the isotopic ratio of key species, such as carbon, sheds light on the properties and origin of these elusive
stars.
Aims. We performed high-resolution observations of SMSS 1605−1443 with the ESPRESSO spectrograph to look for variations in the radial
velocity (vrad) with time. These data have been combined with older MIKE and UVES archival observations to enlarge the temporal baseline. The
12C/
13C isotopic ratio is also studied to explore the possibility of mass transfer from a binary companion.
Methods. A cross-correlation function against a natural template was applied to detect vrad variability and a spectral synthesis technique was used
to derive 12C/
13C in the stellar atmosphere.
Results. We confirm previous indications of binarity in SMSS 1605−1443 and measured a lower limit 12C/
13C > 60 at more than a 3σ confidence
level, proving that this system is chemically unmixed and that no mass transfer from the unseen companion has happened so far. Thus, we confirm
the CEMP-no nature of SMSS 1605−1443 and show that the pristine chemical composition of the cloud from which it formed is currently imprinted
in its stellar atmosphere free of contamination.
The JWST Discovery of the Triply-imaged Type Ia “Supernova H0pe” and Observat...Sérgio Sacani
A Type Ia supernova (SN) at z = 1.78 was discovered in James Webb Space Telescope Near Infrared
Camera imaging of the galaxy cluster PLCK G165.7+67.0 (G165; z = 0.35). The SN is situated 1.5–
2 kpc from its host galaxy Arc 2 and appears in three different locations as a result of gravitational
lensing by G165. These data can yield a value for Hubble’s constant using time delays from this
multiply-imaged SN Ia that we call “SN H0pe.” Over the entire field we identified 21 image multiplicities,
confirmed five of them using Near-Infrared Spectrograph (NIRspec), and constructed a new
lens model that gives a total mass within 600 kpc of (2.6 ± 0.3) × 1014M⊙. The photometry uncovered
a galaxy overdensity at Arc 2’s redshift. NIRSpec confirmed six member galaxies, four of which
surround Arc 2 with relative velocity ≲900 km s−1 and projected physical extent ≲33 kpc. Arc 2
dominates the stellar mass ((5.0±0.1)×1011M⊙), which is a factor of ten higher than other members
of this compact galaxy group. These other group members have specific star formation rates (sSFR)
arXiv:2309.07326v1 [astro-ph.GA] 13 Sep 2023
2 Frye, Pascale, Pierel et al.
of 2–260 Gyr−1 derived from the Hα-line flux corrected for stellar absorption, dust extinction, and slit
losses. Another group centered on the dusty star forming galaxy Arc 1 is at z = 2.24. The total SFR
for the Arc 1 group (≳400M⊙ yr−1) translates to a supernova rate of ∼1 SNe yr−1, suggesting that
regular monitoring of this cluster may yield additional SNe.
TOI-4600 b and c: Two Long-period Giant Planets Orbiting an Early K DwarfSérgio Sacani
We report the discovery and validation of two long-period giant exoplanets orbiting the early K dwarf TOI-4600
(V = 12.6, T = 11.9), first detected using observations from the Transiting Exoplanet Survey Satellite (TESS) by
the TESS Single Transit Planet Candidate Working Group. The inner planet, TOI-4600 b, has a radius of
6.80 ± 0.31 R⊕ and an orbital period of 82.69 days. The outer planet, TOI-4600 c, has a radius of 9.42 ± 0.42 R⊕
and an orbital period of 482.82 days, making it the longest-period confirmed or validated planet discovered by
TESS to date. We combine TESS photometry and ground-based spectroscopy, photometry, and high-resolution
imaging to validate the two planets. With equilibrium temperatures of 347 K and 191 K, respectively, TOI-4600 b
and c add to the small but growing population of temperate giant exoplanets that bridge the gap between hot/warm
Jupiters and the solar system’s gas giants. TOI-4600 is a promising target for further transit and precise RV
observations to measure the masses and orbits of the planets as well as search for additional nontransiting planets.
Additionally, with Transit Spectroscopy Metric values of ∼30, both planets are amenable for atmospheric
characterization with JWST. Together, these will lend insight into the formation and evolution of planet systems
with multiple giant exoplanets.
Artigo que descreve a descoberta do exoplaneta Kepler-432b, um exoplaneta mais massivo que Júpiter que orbita uma estrela gigante vermelha bem próximo e numa órbita extremamente alongada.
A Spatially Resolved Analysis of Star Formation Burstiness by Comparing UV an...Sérgio Sacani
The UltraViolet imaging of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey Fields
(UVCANDELS) program provides Hubble Space Telescope (HST)/UVIS F275W imaging for four CANDELS
fields. We combine this UV imaging with existing HST/near-IR grism spectroscopy from 3D-HST+AGHAST to
directly compare the resolved rest-frame UV and Hα emission for a sample of 979 galaxies at 0.7 < z < 1.5,
spanning a range in stellar mass of 108−11.5 Me. Using a stacking analysis, we perform a resolved comparison
between homogenized maps of rest-UV and Hα to compute the average UV-to-Hα luminosity ratio (an indicator of
burstiness in star formation) as a function of galactocentric radius. We find that galaxies below stellar mass of
∼109.5 Me, at all radii, have a UV-to-Hα ratio higher than the equilibrium value expected from constant star
formation, indicating a significant contribution from bursty star formation. Even for galaxies with stellar mass
109.5 Me, the UV-to-Hα ratio is elevated toward their outskirts (R/Reff > 1.5), suggesting that bursty star
formation is likely prevalent in the outskirts of even the most massive galaxies, but is likely overshadowed by their
brighter cores. Furthermore, we present the UV-to-Hα ratio as a function of galaxy surface brightness, a proxy for
stellar mass surface density, and find that regions below ∼107.5 Me kpc−2 are consistent with bursty star formation,
regardless of their galaxy stellar mass, potentially suggesting that local star formation is independent of global
galaxy properties at the smallest scales. Last, we find galaxies at z > 1.1 to have bursty star formation, regardless of
radius or surface brightness.
Refined parameters of the HD 22946 planetary system and the true orbital peri...Sérgio Sacani
Multi-planet systems are important sources of information regarding the evolution of planets. However, the long-period
planets in these systems often escape detection. These objects in particular may retain more of their primordial characteristics compared
to close-in counterparts because of their increased distance from the host star. HD 22946 is a bright (G = 8.13 mag) late F-type star
around which three transiting planets were identified via Transiting Exoplanet Survey Satellite (TESS) photometry, but the true orbital
period of the outermost planet d was unknown until now.
Aims. We aim to use the Characterising Exoplanet Satellite (CHEOPS) space telescope to uncover the true orbital period of HD 22946d
and to refine the orbital and planetary properties of the system, especially the radii of the planets.
Methods. We used the available TESS photometry of HD 22946 and observed several transits of the planets b, c, and d using CHEOPS.
We identified two transits of planet d in the TESS photometry, calculated the most probable period aliases based on these data, and
then scheduled CHEOPS observations. The photometric data were supplemented with ESPRESSO (Echelle SPectrograph for Rocky
Exoplanets and Stable Spectroscopic Observations) radial velocity data. Finally, a combined model was fitted to the entire dataset in
order to obtain final planetary and system parameters.
Results. Based on the combined TESS and CHEOPS observations, we successfully determined the true orbital period of the planet d
to be 47.42489 ± 0.00011 days, and derived precise radii of the planets in the system, namely 1.362 ± 0.040 R⊕, 2.328 ± 0.039 R⊕, and
2.607 ± 0.060 R⊕ for planets b, c, and d, respectively. Due to the low number of radial velocities, we were only able to determine 3σ
upper limits for these respective planet masses, which are 13.71 M⊕, 9.72 M⊕, and 26.57 M⊕. We estimated that another 48 ESPRESSO
radial velocities are needed to measure the predicted masses of all planets in HD 22946. We also derived stellar parameters for the host
star.
Conclusions. Planet c around HD 22946 appears to be a promising target for future atmospheric characterisation via transmission
spectroscopy. We can also conclude that planet d, as a warm sub-Neptune, is very interesting because there are only a few similar
confirmed exoplanets to date. Such objects are worth investigating in the near future, for example in terms of their composition and
internal structure.
Spirals and clumps in V960 Mon: signs of planet formation via gravitational i...Sérgio Sacani
The formation of giant planets has traditionally been divided into two pathways: core accretion and gravitational instability. However, in recent years, gravitational instability has become less favored, primarily due
to the scarcity of observations of fragmented protoplanetary disks around young stars and low occurrence rate
of massive planets on very wide orbits. In this study, we present a SPHERE/IRDIS polarized light observation
of the young outbursting object V960 Mon. The image reveals a vast structure of intricately shaped scattered
light with several spiral arms. This finding motivated a re-analysis of archival ALMA 1.3 mm data acquired
just two years after the onset of the outburst of V960 Mon. In these data, we discover several clumps of continuum emission aligned along a spiral arm that coincides with the scattered light structure. We interpret the
localized emission as fragments formed from a spiral arm under gravitational collapse. Estimating the mass of
solids within these clumps to be of several Earth masses, we suggest this observation to be the first evidence of
gravitational instability occurring on planetary scales. This study discusses the significance of this finding for
planet formation and its potential connection with the outbursting state of V960 Mon.
Two super-Earths at the edge of the habitable zone of the nearby M dwarf TOI-...Sérgio Sacani
The main scientific goal of TESS is to find planets smaller than Neptune around stars bright enough to allow further characterization studies. Given
our current instrumentation and detection biases, M dwarfs are prime targets to search for small planets that are in (or nearby) the habitable zone
of their host star. Here we use photometric observations and CARMENES radial velocity measurements to validate a pair of transiting planet
candidates found by TESS. The data was fitted simultaneously using a Bayesian MCMC procedure taking into account the stellar variability
present in the photometric and spectroscopic time series. We confirm the planetary origin of the two transiting candidates orbiting around TOI-
2095 (TIC 235678745). The star is a nearby M dwarf (d = 41:90 0:03 pc, Te = 3759 87 K, V = 12:6 mag) with a stellar mass and radius
of M? = 0:44 0:02 M and R? = 0:44 0:02 R, respectively. The planetary system is composed of two transiting planets: TOI-2095b with an
orbital period of Pb = 17:66484 (7 105) days and TOI-2095c with Pc = 28:17232 (14 105) days. Both planets have similar sizes with
Rb = 1:250:07 R and Rc = 1:330:08 R for planet b and c, respectively.We put upper limits on the masses of these objects with Mb < 4:1 M
for the inner and Mc < 7:4 M for the outer planet (95% confidence level). These two planets present equilibrium temperatures in the range of 300
- 350 K and are close to the inner edge of the habitable zone of their star.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Gliese 12 b: A Temperate Earth-sized Planet at 12 pc Ideal for Atmospheric Tr...Sérgio Sacani
Recent discoveries of Earth-sized planets transiting nearby M dwarfs have made it possible to characterize the
atmospheres of terrestrial planets via follow-up spectroscopic observations. However, the number of such planets
receiving low insolation is still small, limiting our ability to understand the diversity of the atmospheric
composition and climates of temperate terrestrial planets. We report the discovery of an Earth-sized planet
transiting the nearby (12 pc) inactive M3.0 dwarf Gliese 12 (TOI-6251) with an orbital period (Porb) of 12.76 days.
The planet, Gliese 12 b, was initially identified as a candidate with an ambiguous Porb from TESS data. We
confirmed the transit signal and Porb using ground-based photometry with MuSCAT2 and MuSCAT3, and
validated the planetary nature of the signal using high-resolution images from Gemini/NIRI and Keck/NIRC2 as
well as radial velocity (RV) measurements from the InfraRed Doppler instrument on the Subaru 8.2 m telescope
and from CARMENES on the CAHA 3.5 m telescope. X-ray observations with XMM-Newton showed the host
star is inactive, with an X-ray-to-bolometric luminosity ratio of log 5.7 L L X bol » - . Joint analysis of the light
curves and RV measurements revealed that Gliese 12 b has a radius of 0.96 ± 0.05 R⊕,a3σ mass upper limit of
3.9 M⊕, and an equilibrium temperature of 315 ± 6 K assuming zero albedo. The transmission spectroscopy metric
(TSM) value of Gliese 12 b is close to the TSM values of the TRAPPIST-1 planets, adding Gliese 12 b to the small
list of potentially terrestrial, temperate planets amenable to atmospheric characterization with JWST.
Gliese 12 b, a temperate Earth-sized planet at 12 parsecs discovered with TES...Sérgio Sacani
We report on the discovery of Gliese 12 b, the nearest transiting temperate, Earth-sized planet found to date. Gliese 12 is a
bright (V = 12.6 mag, K = 7.8 mag) metal-poor M4V star only 12.162 ± 0.005 pc away from the Solar system with one of the
lowest stellar activity levels known for M-dwarfs. A planet candidate was detected by TESS based on only 3 transits in sectors
42, 43, and 57, with an ambiguity in the orbital period due to observational gaps. We performed follow-up transit observations
with CHEOPS and ground-based photometry with MINERVA-Australis, SPECULOOS, and Purple Mountain Observatory,
as well as further TESS observations in sector 70. We statistically validate Gliese 12 b as a planet with an orbital period of
12.76144 ± 0.00006 d and a radius of 1.0 ± 0.1 R⊕, resulting in an equilibrium temperature of ∼315 K. Gliese 12 b has excellent
future prospects for precise mass measurement, which may inform how planetary internal structure is affected by the stellar
compositional environment. Gliese 12 b also represents one of the best targets to study whether Earth-like planets orbiting cool
stars can retain their atmospheres, a crucial step to advance our understanding of habitability on Earth and across the galaxy.
The importance of continents, oceans and plate tectonics for the evolution of...Sérgio Sacani
Within the uncertainties of involved astronomical and biological parameters, the Drake Equation
typically predicts that there should be many exoplanets in our galaxy hosting active, communicative
civilizations (ACCs). These optimistic calculations are however not supported by evidence, which is
often referred to as the Fermi Paradox. Here, we elaborate on this long-standing enigma by showing
the importance of planetary tectonic style for biological evolution. We summarize growing evidence
that a prolonged transition from Mesoproterozoic active single lid tectonics (1.6 to 1.0 Ga) to modern
plate tectonics occurred in the Neoproterozoic Era (1.0 to 0.541 Ga), which dramatically accelerated
emergence and evolution of complex species. We further suggest that both continents and oceans
are required for ACCs because early evolution of simple life must happen in water but late evolution
of advanced life capable of creating technology must happen on land. We resolve the Fermi Paradox
(1) by adding two additional terms to the Drake Equation: foc
(the fraction of habitable exoplanets
with significant continents and oceans) and fpt
(the fraction of habitable exoplanets with significant
continents and oceans that have had plate tectonics operating for at least 0.5 Ga); and (2) by
demonstrating that the product of foc
and fpt
is very small (< 0.00003–0.002). We propose that the lack
of evidence for ACCs reflects the scarcity of long-lived plate tectonics and/or continents and oceans on
exoplanets with primitive life.
A Giant Impact Origin for the First Subduction on EarthSérgio Sacani
Hadean zircons provide a potential record of Earth's earliest subduction 4.3 billion years ago. Itremains enigmatic how subduction could be initiated so soon after the presumably Moon‐forming giant impact(MGI). Earlier studies found an increase in Earth's core‐mantle boundary (CMB) temperature due to theaccumulation of the impactor's core, and our recent work shows Earth's lower mantle remains largely solid, withsome of the impactor's mantle potentially surviving as the large low‐shear velocity provinces (LLSVPs). Here,we show that a hot post‐impact CMB drives the initiation of strong mantle plumes that can induce subductioninitiation ∼200 Myr after the MGI. 2D and 3D thermomechanical computations show that a high CMBtemperature is the primary factor triggering early subduction, with enrichment of heat‐producing elements inLLSVPs as another potential factor. The models link the earliest subduction to the MGI with implications forunderstanding the diverse tectonic regimes of rocky planets.
Climate extremes likely to drive land mammal extinction during next supercont...Sérgio Sacani
Mammals have dominated Earth for approximately 55 Myr thanks to their
adaptations and resilience to warming and cooling during the Cenozoic. All
life will eventually perish in a runaway greenhouse once absorbed solar
radiation exceeds the emission of thermal radiation in several billions of
years. However, conditions rendering the Earth naturally inhospitable to
mammals may develop sooner because of long-term processes linked to
plate tectonics (short-term perturbations are not considered here). In
~250 Myr, all continents will converge to form Earth’s next supercontinent,
Pangea Ultima. A natural consequence of the creation and decay of Pangea
Ultima will be extremes in pCO2 due to changes in volcanic rifting and
outgassing. Here we show that increased pCO2, solar energy (F⨀;
approximately +2.5% W m−2 greater than today) and continentality (larger
range in temperatures away from the ocean) lead to increasing warming
hostile to mammalian life. We assess their impact on mammalian
physiological limits (dry bulb, wet bulb and Humidex heat stress indicators)
as well as a planetary habitability index. Given mammals’ continued survival,
predicted background pCO2 levels of 410–816 ppm combined with increased
F⨀ will probably lead to a climate tipping point and their mass extinction.
The results also highlight how global landmass configuration, pCO2 and F⨀
play a critical role in planetary habitability.
Constraints on Neutrino Natal Kicks from Black-Hole Binary VFTS 243Sérgio Sacani
The recently reported observation of VFTS 243 is the first example of a massive black-hole binary
system with negligible binary interaction following black-hole formation. The black-hole mass (≈10M⊙)
and near-circular orbit (e ≈ 0.02) of VFTS 243 suggest that the progenitor star experienced complete
collapse, with energy-momentum being lost predominantly through neutrinos. VFTS 243 enables us to
constrain the natal kick and neutrino-emission asymmetry during black-hole formation. At 68% confidence
level, the natal kick velocity (mass decrement) is ≲10 km=s (≲1.0M⊙), with a full probability distribution
that peaks when ≈0.3M⊙ were ejected, presumably in neutrinos, and the black hole experienced a natal
kick of 4 km=s. The neutrino-emission asymmetry is ≲4%, with best fit values of ∼0–0.2%. Such a small
neutrino natal kick accompanying black-hole formation is in agreement with theoretical predictions.
Detectability of Solar Panels as a TechnosignatureSérgio Sacani
In this work, we assess the potential detectability of solar panels made of silicon on an Earth-like
exoplanet as a potential technosignature. Silicon-based photovoltaic cells have high reflectance in the
UV-VIS and in the near-IR, within the wavelength range of a space-based flagship mission concept
like the Habitable Worlds Observatory (HWO). Assuming that only solar energy is used to provide
the 2022 human energy needs with a land cover of ∼ 2.4%, and projecting the future energy demand
assuming various growth-rate scenarios, we assess the detectability with an 8 m HWO-like telescope.
Assuming the most favorable viewing orientation, and focusing on the strong absorption edge in the
ultraviolet-to-visible (0.34 − 0.52 µm), we find that several 100s of hours of observation time is needed
to reach a SNR of 5 for an Earth-like planet around a Sun-like star at 10pc, even with a solar panel
coverage of ∼ 23% land coverage of a future Earth. We discuss the necessity of concepts like Kardeshev
Type I/II civilizations and Dyson spheres, which would aim to harness vast amounts of energy. Even
with much larger populations than today, the total energy use of human civilization would be orders of
magnitude below the threshold for causing direct thermal heating or reaching the scale of a Kardashev
Type I civilization. Any extraterrrestrial civilization that likewise achieves sustainable population
levels may also find a limit on its need to expand, which suggests that a galaxy-spanning civilization
as imagined in the Fermi paradox may not exist.
Jet reorientation in central galaxies of clusters and groups: insights from V...Sérgio Sacani
Recent observations of galaxy clusters and groups with misalignments between their central AGN jets
and X-ray cavities, or with multiple misaligned cavities, have raised concerns about the jet – bubble
connection in cooling cores, and the processes responsible for jet realignment. To investigate the
frequency and causes of such misalignments, we construct a sample of 16 cool core galaxy clusters and
groups. Using VLBA radio data we measure the parsec-scale position angle of the jets, and compare
it with the position angle of the X-ray cavities detected in Chandra data. Using the overall sample
and selected subsets, we consistently find that there is a 30% – 38% chance to find a misalignment
larger than ∆Ψ = 45◦ when observing a cluster/group with a detected jet and at least one cavity. We
determine that projection may account for an apparently large ∆Ψ only in a fraction of objects (∼35%),
and given that gas dynamical disturbances (as sloshing) are found in both aligned and misaligned
systems, we exclude environmental perturbation as the main driver of cavity – jet misalignment.
Moreover, we find that large misalignments (up to ∼ 90◦
) are favored over smaller ones (45◦ ≤ ∆Ψ ≤
70◦
), and that the change in jet direction can occur on timescales between one and a few tens of Myr.
We conclude that misalignments are more likely related to actual reorientation of the jet axis, and we
discuss several engine-based mechanisms that may cause these dramatic changes.
The solar dynamo begins near the surfaceSérgio Sacani
The magnetic dynamo cycle of the Sun features a distinct pattern: a propagating
region of sunspot emergence appears around 30° latitude and vanishes near the
equator every 11 years (ref. 1). Moreover, longitudinal flows called torsional oscillations
closely shadow sunspot migration, undoubtedly sharing a common cause2. Contrary
to theories suggesting deep origins of these phenomena, helioseismology pinpoints
low-latitude torsional oscillations to the outer 5–10% of the Sun, the near-surface
shear layer3,4. Within this zone, inwardly increasing differential rotation coupled with
a poloidal magnetic field strongly implicates the magneto-rotational instability5,6,
prominent in accretion-disk theory and observed in laboratory experiments7.
Together, these two facts prompt the general question: whether the solar dynamo is
possibly a near-surface instability. Here we report strong affirmative evidence in stark
contrast to traditional models8 focusing on the deeper tachocline. Simple analytic
estimates show that the near-surface magneto-rotational instability better explains
the spatiotemporal scales of the torsional oscillations and inferred subsurface
magnetic field amplitudes9. State-of-the-art numerical simulations corroborate these
estimates and reproduce hemispherical magnetic current helicity laws10. The dynamo
resulting from a well-understood near-surface phenomenon improves prospects
for accurate predictions of full magnetic cycles and space weather, affecting the
electromagnetic infrastructure of Earth.
Extensive Pollution of Uranus and Neptune’s Atmospheres by Upsweep of Icy Mat...Sérgio Sacani
In the Nice model of solar system formation, Uranus and Neptune undergo an orbital upheaval,
sweeping through a planetesimal disk. The region of the disk from which material is accreted by
the ice giants during this phase of their evolution has not previously been identified. We perform
direct N-body orbital simulations of the four giant planets to determine the amount and origin of solid
accretion during this orbital upheaval. We find that the ice giants undergo an extreme bombardment
event, with collision rates as much as ∼3 per hour assuming km-sized planetesimals, increasing the
total planet mass by up to ∼0.35%. In all cases, the initially outermost ice giant experiences the
largest total enhancement. We determine that for some plausible planetesimal properties, the resulting
atmospheric enrichment could potentially produce sufficient latent heat to alter the planetary cooling
timescale according to existing models. Our findings suggest that substantial accretion during this
phase of planetary evolution may have been sufficient to impact the atmospheric composition and
thermal evolution of the ice giants, motivating future work on the fate of deposited solid material.
Exomoons & Exorings with the Habitable Worlds Observatory I: On the Detection...Sérgio Sacani
The highest priority recommendation of the Astro2020 Decadal Survey for space-based astronomy
was the construction of an observatory capable of characterizing habitable worlds. In this paper series
we explore the detectability of and interference from exomoons and exorings serendipitously observed
with the proposed Habitable Worlds Observatory (HWO) as it seeks to characterize exoplanets, starting
in this manuscript with Earth-Moon analog mutual events. Unlike transits, which only occur in systems
viewed near edge-on, shadow (i.e., solar eclipse) and lunar eclipse mutual events occur in almost every
star-planet-moon system. The cadence of these events can vary widely from ∼yearly to multiple events
per day, as was the case in our younger Earth-Moon system. Leveraging previous space-based (EPOXI)
lightcurves of a Moon transit and performance predictions from the LUVOIR-B concept, we derive
the detectability of Moon analogs with HWO. We determine that Earth-Moon analogs are detectable
with observation of ∼2-20 mutual events for systems within 10 pc, and larger moons should remain
detectable out to 20 pc. We explore the extent to which exomoon mutual events can mimic planet
features and weather. We find that HWO wavelength coverage in the near-IR, specifically in the 1.4 µm
water band where large moons can outshine their host planet, will aid in differentiating exomoon signals
from exoplanet variability. Finally, we predict that exomoons formed through collision processes akin
to our Moon are more likely to be detected in younger systems, where shorter orbital periods and
favorable geometry enhance the probability and frequency of mutual events.
Emergent ribozyme behaviors in oxychlorine brines indicate a unique niche for...Sérgio Sacani
Mars is a particularly attractive candidate among known astronomical objects
to potentially host life. Results from space exploration missions have provided
insights into Martian geochemistry that indicate oxychlorine species, particularly perchlorate, are ubiquitous features of the Martian geochemical landscape. Perchlorate presents potential obstacles for known forms of life due to
its toxicity. However, it can also provide potential benefits, such as producing
brines by deliquescence, like those thought to exist on present-day Mars. Here
we show perchlorate brines support folding and catalysis of functional RNAs,
while inactivating representative protein enzymes. Additionally, we show
perchlorate and other oxychlorine species enable ribozyme functions,
including homeostasis-like regulatory behavior and ribozyme-catalyzed
chlorination of organic molecules. We suggest nucleic acids are uniquely wellsuited to hypersaline Martian environments. Furthermore, Martian near- or
subsurface oxychlorine brines, and brines found in potential lifeforms, could
provide a unique niche for biomolecular evolution.
Continuum emission from within the plunging region of black hole discsSérgio Sacani
The thermal continuum emission observed from accreting black holes across X-ray bands has the potential to be leveraged as a
powerful probe of the mass and spin of the central black hole. The vast majority of existing ‘continuum fitting’ models neglect
emission sourced at and within the innermost stable circular orbit (ISCO) of the black hole. Numerical simulations, however,
find non-zero emission sourced from these regions. In this work, we extend existing techniques by including the emission
sourced from within the plunging region, utilizing new analytical models that reproduce the properties of numerical accretion
simulations. We show that in general the neglected intra-ISCO emission produces a hot-and-small quasi-blackbody component,
but can also produce a weak power-law tail for more extreme parameter regions. A similar hot-and-small blackbody component
has been added in by hand in an ad hoc manner to previous analyses of X-ray binary spectra. We show that the X-ray spectrum
of MAXI J1820+070 in a soft-state outburst is extremely well described by a full Kerr black hole disc, while conventional
models that neglect intra-ISCO emission are unable to reproduce the data. We believe this represents the first robust detection of
intra-ISCO emission in the literature, and allows additional constraints to be placed on the MAXI J1820 + 070 black hole spin
which must be low a• < 0.5 to allow a detectable intra-ISCO region. Emission from within the ISCO is the dominant emission
component in the MAXI J1820 + 070 spectrum between 6 and 10 keV, highlighting the necessity of including this region. Our
continuum fitting model is made publicly available.
WASP-69b’s Escaping Envelope Is Confined to a Tail Extending at Least 7 RpSérgio Sacani
Studying the escaping atmospheres of highly irradiated exoplanets is critical for understanding the physical
mechanisms that shape the demographics of close-in planets. A number of planetary outflows have been observed
as excess H/He absorption during/after transit. Such an outflow has been observed for WASP-69b by multiple
groups that disagree on the geometry and velocity structure of the outflow. Here, we report the detection of this
planet’s outflow using Keck/NIRSPEC for the first time. We observed the outflow 1.28 hr after egress until the
target set, demonstrating the outflow extends at least 5.8 × 105 km or 7.5 Rp This detection is significantly longer
than previous observations, which report an outflow extending ∼2.2 planet radii just 1 yr prior. The outflow is
blueshifted by −23 km s−1 in the planetary rest frame. We estimate a current mass-loss rate of 1 M⊕ Gyr−1
. Our
observations are most consistent with an outflow that is strongly sculpted by ram pressure from the stellar wind.
However, potential variability in the outflow could be due to time-varying interactions with the stellar wind or
differences in instrumental precision.
X-rays from a Central “Exhaust Vent” of the Galactic Center ChimneySérgio Sacani
Using deep archival observations from the Chandra X-ray Observatory, we present an analysis of
linear X-ray-emitting features located within the southern portion of the Galactic center chimney,
and oriented orthogonal to the Galactic plane, centered at coordinates l = 0.08◦
, b = −1.42◦
. The
surface brightness and hardness ratio patterns are suggestive of a cylindrical morphology which may
have been produced by a plasma outflow channel extending from the Galactic center. Our fits of the
feature’s spectra favor a complex two-component model consisting of thermal and recombining plasma
components, possibly a sign of shock compression or heating of the interstellar medium by outflowing
material. Assuming a recombining plasma scenario, we further estimate the cooling timescale of this
plasma to be on the order of a few hundred to thousands of years, leading us to speculate that a
sequence of accretion events onto the Galactic Black Hole may be a plausible quasi-continuous energy
source to sustain the observed morphology
A brief information about the SCOP protein database used in bioinformatics.
The Structural Classification of Proteins (SCOP) database is a comprehensive and authoritative resource for the structural and evolutionary relationships of proteins. It provides a detailed and curated classification of protein structures, grouping them into families, superfamilies, and folds based on their structural and sequence similarities.
Deep Behavioral Phenotyping in Systems Neuroscience for Functional Atlasing a...Ana Luísa Pinho
Functional Magnetic Resonance Imaging (fMRI) provides means to characterize brain activations in response to behavior. However, cognitive neuroscience has been limited to group-level effects referring to the performance of specific tasks. To obtain the functional profile of elementary cognitive mechanisms, the combination of brain responses to many tasks is required. Yet, to date, both structural atlases and parcellation-based activations do not fully account for cognitive function and still present several limitations. Further, they do not adapt overall to individual characteristics. In this talk, I will give an account of deep-behavioral phenotyping strategies, namely data-driven methods in large task-fMRI datasets, to optimize functional brain-data collection and improve inference of effects-of-interest related to mental processes. Key to this approach is the employment of fast multi-functional paradigms rich on features that can be well parametrized and, consequently, facilitate the creation of psycho-physiological constructs to be modelled with imaging data. Particular emphasis will be given to music stimuli when studying high-order cognitive mechanisms, due to their ecological nature and quality to enable complex behavior compounded by discrete entities. I will also discuss how deep-behavioral phenotyping and individualized models applied to neuroimaging data can better account for the subject-specific organization of domain-general cognitive systems in the human brain. Finally, the accumulation of functional brain signatures brings the possibility to clarify relationships among tasks and create a univocal link between brain systems and mental functions through: (1) the development of ontologies proposing an organization of cognitive processes; and (2) brain-network taxonomies describing functional specialization. To this end, tools to improve commensurability in cognitive science are necessary, such as public repositories, ontology-based platforms and automated meta-analysis tools. I will thus discuss some brain-atlasing resources currently under development, and their applicability in cognitive as well as clinical neuroscience.
Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
Ultraviolet-visible spectroscopy refers to absorption spectroscopy or reflect spectroscopy in the UV-VIS spectral region.
Ultraviolet-visible spectroscopy is an analytical method that can measure the amount of light received by the analyte.
Comparing Evolved Extractive Text Summary Scores of Bidirectional Encoder Rep...University of Maribor
Slides from:
11th International Conference on Electrical, Electronics and Computer Engineering (IcETRAN), Niš, 3-6 June 2024
Track: Artificial Intelligence
https://www.etran.rs/2024/en/home-english/
Richard's entangled aventures in wonderlandRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Slide 1: Title Slide
Extrachromosomal Inheritance
Slide 2: Introduction to Extrachromosomal Inheritance
Definition: Extrachromosomal inheritance refers to the transmission of genetic material that is not found within the nucleus.
Key Components: Involves genes located in mitochondria, chloroplasts, and plasmids.
Slide 3: Mitochondrial Inheritance
Mitochondria: Organelles responsible for energy production.
Mitochondrial DNA (mtDNA): Circular DNA molecule found in mitochondria.
Inheritance Pattern: Maternally inherited, meaning it is passed from mothers to all their offspring.
Diseases: Examples include Leber’s hereditary optic neuropathy (LHON) and mitochondrial myopathy.
Slide 4: Chloroplast Inheritance
Chloroplasts: Organelles responsible for photosynthesis in plants.
Chloroplast DNA (cpDNA): Circular DNA molecule found in chloroplasts.
Inheritance Pattern: Often maternally inherited in most plants, but can vary in some species.
Examples: Variegation in plants, where leaf color patterns are determined by chloroplast DNA.
Slide 5: Plasmid Inheritance
Plasmids: Small, circular DNA molecules found in bacteria and some eukaryotes.
Features: Can carry antibiotic resistance genes and can be transferred between cells through processes like conjugation.
Significance: Important in biotechnology for gene cloning and genetic engineering.
Slide 6: Mechanisms of Extrachromosomal Inheritance
Non-Mendelian Patterns: Do not follow Mendel’s laws of inheritance.
Cytoplasmic Segregation: During cell division, organelles like mitochondria and chloroplasts are randomly distributed to daughter cells.
Heteroplasmy: Presence of more than one type of organellar genome within a cell, leading to variation in expression.
Slide 7: Examples of Extrachromosomal Inheritance
Four O’clock Plant (Mirabilis jalapa): Shows variegated leaves due to different cpDNA in leaf cells.
Petite Mutants in Yeast: Result from mutations in mitochondrial DNA affecting respiration.
Slide 8: Importance of Extrachromosomal Inheritance
Evolution: Provides insight into the evolution of eukaryotic cells.
Medicine: Understanding mitochondrial inheritance helps in diagnosing and treating mitochondrial diseases.
Agriculture: Chloroplast inheritance can be used in plant breeding and genetic modification.
Slide 9: Recent Research and Advances
Gene Editing: Techniques like CRISPR-Cas9 are being used to edit mitochondrial and chloroplast DNA.
Therapies: Development of mitochondrial replacement therapy (MRT) for preventing mitochondrial diseases.
Slide 10: Conclusion
Summary: Extrachromosomal inheritance involves the transmission of genetic material outside the nucleus and plays a crucial role in genetics, medicine, and biotechnology.
Future Directions: Continued research and technological advancements hold promise for new treatments and applications.
Slide 11: Questions and Discussion
Invite Audience: Open the floor for any questions or further discussion on the topic.
1. Draft version October 21, 2015
Preprint typeset using LATEX style emulateapj v. 5/2/11
‘REFSDAL’ MEETS POPPER: COMPARING PREDICTIONS OF THE RE-APPEARANCE OF THE
MULTIPLY IMAGED SUPERNOVA BEHIND MACSJ1149.5+2223
T. Treu1,2
, G. Brammer3
, J. M. Diego4
, C. Grillo5
, P. L. Kelly6
, M. Oguri7,8,9
, S. A. Rodney10,11,12
, P. Rosati13
,
K. Sharon14
, A. Zitrin15,12
, I. Balestra16
, M. Bradaˇc17
, T. Broadhurst18,19
, G. B. Caminha13
, M. Ishigaki20,8
,
R. Kawamata21
, T. L. Johnson14
, A. Halkola, A. Hoag17
, W. Karman22
, A. Mercurio23
, K. B. Schmidt24
,
L.-G. Strolger3,25
, and S. H. Suyu26
Draft version October 21, 2015
ABSTRACT
Supernova ‘Refsdal’, multiply imaged by cluster MACS1149.5+2223, represents a rare opportunity
to make a true blind test of model predictions in extragalactic astronomy, on a time scale that is
short compared to a human lifetime. In order to take advantage of this event, we produced seven
gravitational lens models with five independent methods, based on Hubble Space Telescope (HST)
Hubble Frontier Field images, along with extensive spectroscopic follow-up from HST and from the
Very Large Telescope. We compare the model predictions and show that they agree reasonably well
with the measured time delays and magnification ratios between the known images, even though
these quantities were not used as input. This agreement is encouraging, considering that the models
only provide statistical uncertainties, and do not include additional sources of uncertainties such as
structure along the line of sight, cosmology, and the mass sheet degeneracy. We then present the
model predictions for the other appearances of SN ‘Refsdal’. A future image will reach its peak in the
first half of 2016, while another image appeared between 1994 and 2004. The past image would have
been too faint to be detected in archival images. The future image should be approximately one third
as bright as the brightest known images and thus detectable in HST images, as soon as the cluster
can be targeted again (beginning 2015 October 30). We will find out soon whether our predictions
are correct.
Subject headings: gravitational lensing: strong
tt@astro.ucla.edu
1 Department of Physics and Astronomy, University of Cali-
fornia, Los Angeles, CA 90095
2 Packard Fellow
3 Space Telescope Science Institute, 3700 San Martin Dr., Bal-
timore, MD 21218, USA
4 IFCA, Instituto de F´ısica de Cantabria (UC-CSIC), Av. de
Los Castros s/n, 39005 Santander, Spain
5 Dark Cosmology Centre, Niels Bohr Institute, University of
Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen, Den-
mark
6 Department of Astronomy, University of California, Berke-
ley, CA 94720-3411, USA
7 Kavli Institute for the Physics and Mathematics of the Uni-
verse (Kavli IPMU, WPI), University of Tokyo, 5-1-5 Kashi-
wanoha, Kashiwa, Chiba 277-8583, Japan
8 Department of Physics, University of Tokyo, 7-3-1 Hongo,
Bunkyo-ku, Tokyo 113-0033, Japan
9 Research Center for the Early Universe, University of Tokyo,
7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
10 Department of Physics and Astronomy, University of South
Carolina, 712 Main St., Columbia, SC 29208, USA
11 Department of Physics and Astronomy, The Johns Hopkins
University, 3400 N. Charles St., Baltimore, MD 21218, USA
12 Hubble Fellow
13 Dipartimento di Fisica e Scienze della Terra, Universit`a
degli Studi di Ferrara, via Saragat 1, I-44122, Ferrara, Italy
14 Department of Astronomy, University of Michigan, 1085 S.
University Avenue, Ann Arbor, MI 48109, USA
15 California Institute of Technology, 1200 East California
Boulevard, Pasadena, CA 91125
16 University Observatory Munich, Scheinerstrasse 1, D-81679
Munich, Germany
17 University of California Davis, 1 Shields Avenue, Davis, CA
95616
18 Fisika Teorikoa, Zientzia eta Teknologia Fakultatea, Euskal
Herriko Unibertsitatea UPV/EHU
19 IKERBASQUE, Basque Foundation for Science, Alameda
Urquijo, 36-5 48008 Bilbao, Spain
20 Institute for Cosmic Ray Research, The University of
Tokyo, Kashiwa, Chiba 277-8582, Japan
21 Department of Astronomy, Graduate School of Science, The
University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033,
Japan
22 Kapteyn Astronomical Institute, University of Groningen,
Postbus 800, 9700 AV Groningen, the Netherlands
23 INAF, Osservatorio Astronomico di Bologna, via Ranzani
1, I-40127 Bologna, Italy
24 Department of Physics, University of California, Santa Bar-
bara, CA 93106-9530, USA
25 Department of Physics, Western Kentucky University,
Bowling Green, KY 42101, USA
26 Institute of Astronomy and Astrophysics, Academia Sinica,
P.O. Box 23-141, Taipei 10617, Taiwan
arXiv:1510.05750v1[astro-ph.CO]20Oct2015
2. 2 Treu et al. (2015)
1. INTRODUCTION
In 1964 Sjur Resfdal speculated that a supernova mul-
tiply imaged by a foreground massive galaxy could be
used to measure distances and, therefore, the Hubble
Constant (Refsdal 1964). The basic physics behind this
phenomenon is very simple. According to Fermat’s prin-
ciple, in gravitational optics as in standard optics, mul-
tiple images form at the extrema of the excess arrival
time (Schneider 1985; Blandford & Narayan 1986). The
excess arrival time is the result of the competition be-
tween the geometric time delay and the Shapiro (1964)
delay. The arrival time thus depends on the apparent
position of the image on the sky as well as the gravita-
tional potential. Since the arrival time is measured in
seconds, while all the other lensing observables are mea-
sured in angles on the sky, their relationship depends on
the angular diameter distance D. In the simplest case of
single plane lensing the time delay between two images
is proportional to the so-called time-delay distance, i.e.
DdDs(1+zd)/Dds, where d and s represent the deflector
and the source, respectively, and the so-called Fermat
potential (see, e.g., Meylan et al. 2006; Treu 2010; Suyu
et al. 2010).
Over the past decades many authors have highlighted
the importance and applications of identifying such
events (e.g., Kolatt & Bartelmann 1998; Holz 2001; Goo-
bar et al. 2002; Bolton & Burles 2003; Oguri & Kawano
2003), computed rates and proposed search strategies
(Linder et al. 1988; Sullivan et al. 2000; Oguri et al. 2003;
Oguri & Marshall 2010), and identified highly magnified
supernova (Quimby et al. 2014). Finally, 50 years after
the initial proposal by Refsdal, the first multiply imaged
supernova was discovered in November 2014 (Kelly et al.
2015) in Hubble Space Telescope (HST) images of the
cluster MACSJ1149.5+2223 (Ebeling et al. 2007; Smith
et al. 2009; Zitrin & Broadhurst 2009), taken as part of
the Grism Lens Amplified Survey from Space (GLASS;
GO-13459, PI Treu; Schmidt et al. 2014; Treu et al.
2015), and aptly nicknamed ’Refsdal’. SN ‘Refsdal’ was
identified in di↵erence imaging as four point-sources that
were not present in earlier images taken as part of the
CLASH survey (Postman et al. 2012). Luckily, the event
was discovered just before the beginning of an intensive
imaging campaign as part of the Hubble Frontier Field
(HFF) initiative (Lotz et al. 2015, in preparation; Coe
et al. 2015). Additional epochs were obtained as part of
the FrontierSN program (GO-13790. PI: Rodney), and a
director discretionary time program (GO/DD-14041. PI:
Kelly). The beautiful images that have emerged (Fig-
ure 1) are an apt celebration of the international year of
light and the one hundredth anniversary of the theory of
general relativity (e.g., Treu & Ellis 2015).
The gravitational lensing configuration of the ‘Refsdal’
event is very remarkable. The supernova exploded in one
arm of an almost face-on spiral galaxy that is multiply
imaged and highly magnified by the cluster gravitational
potential. Furthermore, the spiral arm hosting ‘Refs-
dal’ happens to be su ciently close to a cluster member
galaxy that four additional multiple images are formed
with average separation of order arcseconds, i.e., typi-
cal of galaxy-scale strong lensing. This set of four im-
ages close together in an “Einstein cross” configuration
is where ‘Refsdal’ has been detected so far (labeled S1-
S4 in Figure 1). As we discuss below, the cluster-scale
images are more separated in terms of their arrival time,
with time delays that can be much longer than the dura-
tion of the event, and therefore it is consistent with the
lensing interpretation that they have not been seen yet.
The original suggestion by Refsdal (1964) was to use
such events to measure distances and therefore cosmo-
logical parameters, starting from the Hubble constant.
While distances with interesting accuracy and precision
have been obtained from gravitational time delays in
galaxy scale systems lensing quasars (e.g., Suyu et al.
2014), it is premature to attempt this in the case of ‘Refs-
dal’. The time delay is not yet known with precision com-
parable to that attained for lensed quasars (e.g., Tewes
et al. 2013b), and the mass distribution of the cluster
MACSJ1149.5+2223 is inherently much more complex
than that of a single elliptical galaxy.
However, ‘Refsdal’ gives us a unique opportunity to
test the current mass models of MACSJ1149.5+2223, by
conducting a textbook-like falsifiable experiment (Pop-
per 1992). All the models that have been published after
the discovery of ‘Refsdal’ (Kelly et al. 2015; Oguri 2015;
Sharon & Johnson 2015; Diego et al. 2015; Jauzac et al.
2015) predict that an additional image will form some
time in the near future (near image 1.2 of the host galaxy,
shown in Figure 1). It could appear as early as October
2015 or in a few years. The field of MACSJ1149.5+2223
is currently unobservable with HST, but observations will
resume at the end of October 2015 as part of an ap-
proved cycle 23 program (GO-14199. PI: Kelly). We
thus have the opportunity to carry out a true blind test
of the models, if we act fast enough. This test is similar in
spirit to the test of magnification models using supernova
‘Tomas’, a Type-Ia SN magnified by Abell 2744 (Rodney
et al. 2015). The uniqueness of our test lies in the fact
that it is based on the prediction of an event that has
not happened yet and it is thus intrinsically blind and
immune from experimenter bias.
The quality and quantity of data available to lens mod-
elers have improved significantly since the discovery of
‘Refsdal’ and the publication of the first modeling papers.
As part of the HFF and follow-up programs there are
now significantly deeper multiband HST images. Spec-
troscopy for hundreds of sources in the field (Figure 1)
is now available from HST grism data obtained as part
of GLASS and ‘Refsdal’ follow-up (aimed primarily at
typing the supernova; Kelly et al. 2015, in prepara-
tion), as well as from Multi Unit Spectroscopic Explorer
(MUSE) Very Large Telescope (VLT) Director’s Discre-
tionary Time follow-up (PI: Grillo).
The timing is thus perfect to ask the question: “Given
state of the art data and models, how accurately can we
predict the arrival time and magnification of the next
appearance of a multiply-imaged supernova?” Answer-
ing this question will give us an absolute measurement of
the quality of present-day models, although one should
keep in mind that this is a very specific test. The arrival
time and especially the magnification of a point source
depend strongly on the details of the gravitational po-
tential in the vicinity of the images. Additional uncer-
tainties on the time delay and magnification arise from
the inhomogenous distribution of mass along the line of
sight (Suyu et al. 2010; Collett et al. 2013; Greene et al.
2013), the mass-sheet degeneracy and its generalizations
3. MACS1149 Forecasts 3
Figure 1. Multiple images of the SN ‘Refsdal’ host galaxy behind MACS1149. The left panel shows a wide view of the cluster,
encompassing the entire footprint of the WFC3-IR camera. Spectroscopically confirmed cluster member galaxies are highlighted in magenta
circles. Cyan circles indicate those associated with the cluster based on their photometric properties. The three panels on the right show
in more detail the multiple images of the SN ‘Refsdal’ host galaxy (labeled 1.1 1.2 and 1.3). The positions of the known images of ’Refsdal’
are labeled as S1-S4, while the model-predicted locations of the future and past appearance are labeled as SX and SY, respectively.
(Falco et al. 1985; Schneider & Sluse 2013, 2014; Suyu
et al. 2014; Xu et al. 2015), and the residual uncertain-
ties in cosmological parameters, especially the Hubble
Constant (Riess et al. 2011; Freedman et al. 2012). Av-
erage or global quantities of more general interest, such
as the total volume behind the cluster, or the average
magnification, are much less sensitive to the details of
the potential around a specific point.
In order to answer this question in the very short
amount of time available, the ‘Refsdal’ follow-up team
worked hard to reduce and analyze the follow-up data.
By May 2015 it was clear that the quality of the follow-
up data would be su cient to make substantial improve-
ments to their lens models. Therefore the follow-up team
contacted the three other groups who had by then pub-
lished predictions for ‘Refsdal’, and o↵ered them the new
datasets to update their models, as part of a concerted
comparison e↵ort. Thus, the five groups worked together
to incorporate the new information into lensing analy-
sis, first by identifying and rigorously vetting new sets of
multiple images, and then to update their models in time
to make a timely prediction. A synopsis and comparison
between the results and predictions of the various mod-
els is presented in this paper. Companion papers by the
individual groups will describe the follow-up campaigns
as well as the details of each modeling e↵ort.
This paper is organized as follows. In Section 2, we
briefly summarize the datasets and measurements that
are used in this comparison e↵ort. In Section 3, we review
the constraints used by the modeling teams. Section 4
gives a concise description of each of the five lens mod-
eling techniques adopted. Section 5 presents the main
results of this paper, i.e. a comparison of the predictions
of the di↵erent models. Section 6 discusses the results,
and Section 7 concludes with a summary. To ensure uni-
formity with the modeling e↵ort for the Hubble Frontier
Fields clusters, we adopt a concordance cosmology with
h = 0.7, ⌦m = 0.3, and ⌦⇤ = 0.7. All magnitudes are
given in the AB system.
2. SUMMARY OF DATASETS AND MEASUREMENTS
We briefly summarize the datasets and measurements
used in this paper. An overview of the field of view and
pointing of the instruments used in this paper is shown
in Figure 2.
2.1. HST imaging
4. 4 Treu et al. (2015)
Di↵erent versions of the images were used at di↵erent
stages of the process. However, the final identification
of multiple images and their positions were based on the
HFF data release v1.0, and their world coordinate sys-
tem. The reader is referred to the HFF data release
webpages27
for more information on this data.
2.1.1. The light curves of SN ‘Refsdal’
Two teams measured the light curves of ‘Refsdal’ inde-
pendently and derived initial measurements of the time
delays and magnification ratios. The di↵erence between
the two measurements provides an estimate of the sys-
tematic uncertainties associated with the measurement,
even though both measurements ignore e↵ects like mi-
crolensing fluctuations (Dobler & Keeton 2006), and
therefore this should be considered as a lower limit to
the total uncertainty. A third e↵ort (Rodney et al. 2015,
in preparation) is under way to determine the time de-
lays using methods developed for lensed quasars (Tewes
et al. 2013a) that do not use a template for the light
curve. Preliminary results from this third method indi-
cate time delays and magnifications consistent with those
presented here, albeit with larger uncertainties, as ex-
pected for the more flexibile procedure. More details
about the supernova light curve, final measurements of
time delays and magnification ratios and their uncertain-
ties will be presented separately by each team in forth-
coming publications.
The measurement of the first team (Kelly et al.), is
based on the wide-band F160W (approximately rest-
frame R band) WFC3-IR light curves from imaging taken
between 2014 November 11 and 2015 July 21. The
F160W photometry of S1–S4 was fit with the R-band
light curves of SN 1987A (Hamuy & Suntze↵ 1990) and
three additional events showing similar luminosity evo-
lution: NOOS-005 (I band)28
, SN 2006V (r band; Tad-
dia et al. 2012), and SN 2009E (R band; Pastorello
et al. 2012). The team first performed a spline interpola-
tion of the comparison light curves, and then iteratively
searched for the light-curve normalization and date of
maximum that provide the best fit to the photometry
of each SN image. The uncertainties in Table 1 are the
standard deviation among the time delays and magni-
fications for the four light-curve templates. The peak
brightness of image S1 occured approximately on 2015
April 26 (±20 days in the observer frame). We note that
the light curve is very extended in time, and the time of
the peak brightness is more uncertain than the relative
time delay.
The second team (Strolger et al.) proceeded as fol-
lows. The multiple exposures on the target field of
MACSJ1149+2223 were combined in visits, 2 to 4 ex-
posure combinations by passband, each typically about
250, 1200, and 5000 seconds in total exposure time. Each
visit-based filter combination was corrected to a rectified
astrometric grid using DrizzlePac routines. Photometric
measures were made with aperture photometry using the
weighted average of circular apertures of r = 2, 3, and
4 pixels, corrected to infinite aperture magnitudes using
encircled energy tables from Sirianni et al. (2005, ACS)
and the WFC3 instrument handbook.
27 http://www.stsci.edu/hst/campaigns/frontier-fields/
28 http://ogle.astrouw.edu.pl/ogle3/ews/NOOS/2003/noos.html
Table 1
Measured time delays and magnification ratios
Image pair t (K) µ ratio (K) t (S) µ ratio (S)
(days) (days)
S2 S1 -2.1±1.0 1.09±0.01 -9.0 1.06
S3 S1 5.6±2.2 1.04±0.02 -11 0.87
S4 S1 22±11 0.35±0.01 15.6 0.36
Note. — Observed delays and relative magnifications be-
tween the images S1–S4 of SN ‘Refsdal’. For the values in
column 2 and 3 Kelly et al. have fit the WFC3-IR F160W
photometry of the images using the light curves of four sep-
arate 87A-like SN. The uncertainties listed are the standard
deviation among the estimates made using the four light-curve
templates, and may significantly underestimate the actual un-
certainty. The values listed in column 4 and 5 are obtained
independently by Strolger et al., and have similar uncertain-
ties.
The light curve and spectral models in
SNANA (Kessler et al. 2009) were used to con-
struct multi-passband template light curves for five SN
types (Ia, IIP, IIL/n, and Ib/c), corrected to appear
as they would at the redshift of the event and through
the observed passbands. An artificial SN 1987A-like
model was then added, based on optical observations
of SN 1987A (Hamuy & Suntze↵ 1990), de-reddened
by an E(B V ) = 0.16 (Fitzpatrick & Walborn 1990)
and RV = 4.5 (De Marchi & Panagia 2014) appropriate
for the region of the Large Magellanic Cloud where
SN 1987A appeared. The goodness of fit was evaluated
through a least-squares fit (as 2
⌫) to the multi-passband
data for each image independently, with magnification
and date of maximum light as free parameters. The
slow rise of SN ‘Refsdal’ to maximum light (⇠200 days
observed, ⇠80 days in the rest-frame R-passband) was
seen early on to be generally inconsistent with the rise
times for the common SN types, but broadly consistent
with the rise of SN 1987A-like events, taking time
delation into account. The best fit to all four images was
found to be the SN 1987A-like template, with 2
⌫ < 28
for all images. The low quality of fit can be attributed
principally to the di↵erence in color between SN 1987A
and the much bluer SN ‘Refsdal’, as well as the relative
lack of flexibility in using a single template to represent
a heterogeneous SN class. These fits were improved
( 2
⌫ < 10) by adding non-positive extinction correction,
with AV = 2.1 (assuming RV = 4.05).
2.2. Spectroscopy
2.2.1. HST spectroscopy
The HST grism spectroscopy is comprised of two
datasets. The GLASS data consist of 10 orbits of ex-
posures taken through the G102 grism and 4 orbits of
exposures taken through the G141 grism, spanning the
wavelength range 0.81 1.69µm. The GLASS data were
taken at two approximately orthogonal position angles to
mitigate contamination by nearby sources (the first one
in 2014 February 23-25, the second PA in 2014 November
3-11). The ‘Refsdal’ follow-up e↵ort was focused on the
G141 grism, reaching a depth of 30 orbits. The point-
ing and position angle of the follow-up grism data were
5. MACS1149 Forecasts 5
Figure 2. Observational layout of the MUSE and HST spectroscopy in the context of existing imaging data for MACSJ1149.5+2223.
The “Full F160W” polygon is the full footprint of the F160W v1.0 FF release image. The numbers in parentheses in the spectroscopy
panel at the right are the number of orbits per grism in each of two orients. The background image has been taken with the MOSFIRE
instrument on the W.M.Keck-I Telescope (Brammer et al. 2015, in preparation).
chosen to optimize the spectroscopy of the supernova it-
self, and are therefore di↵erent from the ones adopted
by GLASS. The ‘Refsdal’ follow-up spectra were taken
between 2014 December 23 and 2015 January 4. Only
a brief description of the data is given here. For more
details the reader is referred to Schmidt et al. (2014) and
Treu et al. (2015) for GLASS, and Brammer et al. (2015,
in preparation) and Kelly et al. (2015, in preparation)
for the deeper follow-up data.
The observing strategies and data reduction schemes
were very similar for the two datasets, building on previ-
ous work by the 3D-HST survey (Brammer et al. 2012).
At least 4 sub-exposures were taken during each visit
with semi-integer pixel o↵sets. This enables rejection of
defects and cosmic rays as well as recovery of some of
the resolution lost to undersampling of the PSF through
interlacing. The data were reduced with an updated ver-
sion of the 3D-HST reduction pipeline29
described by
Brammer et al. (2012) and Momcheva et al. (2015). The
pipeline takes care of alignment, defect removal, back-
ground removal, image combination, and modeling of
contamination by nearby sources. One and two dimen-
sional spectra are extracted for each source.
The spectra were inspected independently by two of
us (T.T. and G.B.) using custom tools and the in-
terfaces GiG and GiGz (available at https://github.
com/kasperschmidt/GLASSinspectionGUIs) developed
as part of the GLASS project. Information obtained
from the multiband photometry, continuum, and emis-
sion line was combined to derive a redshift and quality
flag. The few discrepancies between redshifts and quality
flags were resolved by mutual agreement. In the end, we
determined redshifts for 389 sources, with quality 3 or 4
29 http://code.google.com/p/threedhst/
Table 2
Redshift catalog
ID? RA DEC z quality source Notes
(J2000) (J2000)
1 177.397188 22.393744 0.0000 4 2 · · ·
2 177.404017 22.403067 0.5660 4 2 · · ·
3 177.394525 22.400653 0.5410 4 2 · · ·
4 177.399663 22.399597 0.5360 4 2 · · ·
5 177.404054 22.392108 0.0000 4 2 · · ·
6 177.398554 22.389792 0.5360 4 2 · · ·
7 177.393010 22.396799 2.9490 4 2 · · ·
8 177.394400 22.400761 2.9490 4 2 · · ·
9 177.404192 22.406125 2.9490 4 2 · · ·
10 177.392904 22.404014 0.5140 4 2 · · ·
Note. — First entries of the redshift catalog. The full catalog
is given in its entirety in the electronic edition. The column “qual-
ity” contains the quality flag (3=secure, 4=probable). The column
“source” gives the original source of the redshift (1=HST, Brammer
et al. 2015, in prep; 2=MUSE, Grillo et al. 2015, in prep; 3=both).
The column “note” lists special comments about the object, e.g. if
the object is part of a known multiply image system.
(probable or secure, respectively, as defined by Treu et
al. 2015).
2.2.2. VLT spectroscopy
Integral field spectroscopy was obtained with the
MUSE instrument on the VLT between 2015 February
14 and 2015 April 12, as part of a Director Discretionary
Time program to followup ‘Refsdal’ (PI: Grillo). The
main goal of the program was to facilitate the computa-
tion of an accurate model to forecast the next appearance
of the lensed SN. MUSE covers the wavelength range 480-
8. 8 Treu et al. (2015)
2.2.3. Combined redshift catalog
Redshifts for 70 objects were measured independently
using both MUSE and GLASS data. We find that the
redshifts of all objects in common agree within the un-
certainties, attesting to the excellent quality of the data.
The final redshift catalog, comprising of 429 entries, is
given in electronic format in in Table 2, and is avail-
able through the GLASS public website at URL https:
//archive.stsci.edu/prepds/glass/. We note that
owing to the high resolution of the MUSE data we im-
proved the precision of the redshift of the Refsdal host
galaxy to z = 1.488 (c.f. 1.491 previously reported by
Smith et al. 2009). Also, we revise the redshift of the
multiply imaged source 3 with the new and reliable mea-
surement z = 3.129 based on unequivocal multiple line
identifications ([OII] in the grism data, plus Lyman↵ in
the MUSE data).
3. SUMMARY OF LENS MODELING CONSTRAINTS
3.1. Multiple images
The strong lensing models that are considered in this
paper use as constraints sets of multiply-imaged lensed
galaxies, as well as knots in the host galaxy of SN ‘Refs-
dal’. The five teams independently evaluated known sets
of multiple images (Zitrin & Broadhurst 2009; Smith
et al. 2009; Johnson et al. 2014; Sharon & Johnson 2015;
Diego et al. 2015), and suggested new identifications
of image across the entire field of view, based on the
new HFF data. In evaluating the image identifications,
the teams relied on their preliminary lens models and
the newly measured spectroscopic redshifts (Section 2.2).
Each team voted on known and new system on a scale of
1–4, where 1 denotes secure identification, 2 is a possible
identification, and higher values are considered unreli-
able. Images that had large variance in their scores were
discussed and re-evaluated, and the final score was then
recorded. The list of multiple images considered in this
work is given in Table 3. For each system we give coor-
dinates, average score, and redshift if available. We also
indicate the labels given to known images that were pre-
viously identified in the literature, previously published
redshifts, and references to these publications.
We define three samples of image sets, “gold”, “sil-
ver”, and “all”, based on the voting process. Following
the approach of Wang et al. (2015), we conservatively
include in our “gold” sample only the systems that every
team was confident about. The “silver” sample includes
images that were considered secure by most teams, or
are outside the MUSE field of view. The “all” sample
includes all the images that were not rejected as false
identification, based on imaging and/or spectroscopy. In
order to facilitate the comparison, most teams produced
baseline models based on the “gold” sample of images,
and some of the teams produced additional models based
on larger sets of images. However, owing to di↵erences in
investigator’s opinions and specifics of each code, small
di↵erences between the constraints adopted by each team
persist. They are described below for each of the teams.
The reader is referred to the publications of each indi-
vidual team for more details.
We also evaluated the identification of knots in the
grand design spiral galaxy hosting ‘Refsdal’. Table 4 and
Figure 3 list the emission knots and features in the host
galaxy of SN ‘Refsdal’ that were considered in this work.
Not all knots were used in all models, and again, there are
slight di↵erences between the teams as the implementa-
tion of these constraints vary among lensing algorithms.
Nevertheless, the overall mapping of morphological fea-
tures between the images of this galaxy was in agreement
between the modeling teams.
3.2. Time delays
The time delay and magnification ratios between the
known images were not yet measured at the time when
the models were being finalized. Therefore they were not
used as input and they can be considered as a valuable
test of the lens model.
3.3. Cluster members
Cluster member galaxies were selected based on their
redshifts in the combined redshift catalog and their pho-
tometry, as follows. In order to account for the clus-
ter velocity dispersion, as well as the uncertainty on
the grism-based redshifts, we define cluster member-
ship loosely as galaxies with spectroscopic redshift in
the range 0.520 < z < 0.570, i.e. within a few thou-
sand kilometers per second of the fiducial cluster redshift
(z = 0.542). This is su ciently precise for the purpose
of building lens models, even though not all the cluster
members are necessarily physically bound to the cluster,
from a dynamical point of view. Naturally, these clus-
ter members still contribute to the deflection field as the
dynamically bound cluster members. The spectroscopic
cluster-member catalog comprises 170 galaxies.
To obtain a more complete member catalog, the
spectroscopically-confirmed members were supplemented
by photometrically selected galaxies. This list includes
galaxies down to the magnitude limit (F814W⇠25) of
spectroscopically confirmed members. It is constituted
mostly of galaxies belonging to the last two-magnitude
bins of the luminosity distribution, for which the spec-
troscopic sample is significantly incomplete. The missing
galaxies from the spectroscopic catalog are the bright-
est ones that fall outside the MUSE field of view or the
ones that are contaminated in the HST grism data. The
photometric analysis is restricted to the WFC3-IR area,
in order to exploit the full multi-band photometric cat-
alog from CLASH. The method is briefly described by
Grillo et al. (2015), and it uses a Bayesian technique
to compute the probability for a galaxy to be a mem-
ber from the distribution in color space of all spectro-
scopic galaxies (from 13 bands, i.e. not including the
3 in the UV). For the photometric selection, we started
from spectroscopically confirmed members, with redshift
within 0.520 < z < 0.570, and provided a catalog with
only the objects with measured F160W magnitudes. The
total catalog of cluster members comprises 170 galaxies
with spectroscopically determined membership, and 136
galaxies with photometrically determined membership.
9. MACS1149 Forecasts 9
Figure 3. Knots and morphological features in the host galaxy of SN ‘Refsdal’ at z = 1.488. The color composite on which the regions are
overplotted is generated by scaling and subtracting the F814W image from the F435W, F606W, and F105W images, in order to suppress
the light from the foreground cluster galaxies. The left panel shows image 1.1, and the right panel shows image 1.3. In the middle panel,
the complex lensing potential in the central region is responsible for one full image, 1.2, and additional partial images of the galaxy, 1.4,
and 1.5 (see also Smith et al. 2009, Zitrin et al. 2009, and Sharon & Johnson 2015). To guide the eye, we label knots that belong to 1.4
and 1.5 in cyan and yellow, respectively. A possible sixth image of a small region of the galaxy is labeled in green. The two features marked
with an asterisks in this panel, *1.5 and *13, are the only controversial identifications. We could not rule out the identification of *1.5
(knot 1.1.5 in Table 4) as counterpart of the bulge of the galaxy, however, it is likely only partly imaged. Image *13 (1.13.6 in Table 4) is
suggested by some of the models, but hard to confirm, and is thus not used as constraints in the “gold” lens models considered here. We
note that the exact coordinates of each feature may vary slightly between modelers, and we refer the reader to detailed publications (in
preparation) by each modeling team for exact positions and features used.
Table 4
Knots in the host galaxy of ’Refsdal’
ID R.A. (J2000) Decl. (J2000) ID Smith et al. (2009) ID Sharon et al. (2015) ID Diego et al. (2015) Notes
1.1.1 177.39702 22.396003 2 1.1 1.1.1 1
1.1.2 177.39942 22.397439 2 1.2 1.2.1 1
1.1.3 177.40341 22.402444 2 1.3 1.3.1 1
1.*1.5 177.39986 22.397133 · · · · · · 1.5.1 1,2
1.2.1 177.39661 22.396308 19 23.1 1.1.8 · · ·
1.2.2 177.39899 22.397867 19 23.2 1.2.8 · · ·
1.2.3 177.40303 22.402681 19 23.3 1.3.8 · · ·
1.2.4 177.39777 22.398789 19 23.4 1.4.8a · · ·
1.2.6 177.39867 22.398242 · · · · · · 1.4.8b · · ·
1.3.1 177.39687 22.396219 16 31.1 1.1.15 · · ·
1.3.2 177.39917 22.397600 16 31.2 1.2.15 · · ·
1.3.3 177.40328 22.402594 16 31.3 1.3.15 · · ·
1.4.1 177.39702 22.396214 11 32.1 · · · · · ·
1.4.2 177.39923 22.397483 11 32.2 · · · · · ·
1.4.3 177.40339 22.402558 11 32.3 · · · · · ·
1.5.1 177.39726 22.396208 18 33.1 · · · · · ·
1.5.2 177.39933 22.397303 18 33.2 · · · · · ·
1.5.3 177.40356 22.402522 18 33.3 · · · · · ·
1.6.1 177.39737 22.396164 · · · · · · 1.1.13 · · ·
1.6.2 177.39945 22.397236 · · · · · · 1.2.13 · · ·
1.6.3 177.40360 22.402489 · · · · · · 1.3.13 · · ·
1.7.1 177.39757 22.396114 · · · 40.1 · · · · · ·
1.7.2 177.39974 22.396933 · · · 40.2 · · · · · ·
1.7.3 177.40370 22.402406 · · · 40.3 · · · · · ·
1.8.1 177.39795 22.396014 · · · · · · · · · · · ·
1.8.2 177.39981 22.396750 · · · · · · · · · · · ·
1.8.3 177.40380 22.402311 · · · · · · · · · · · ·
1.9.1 177.39803 22.395939 · · · · · · 1.1.9 · · ·
1.9.2 177.39973 22.396983 · · · · · · 1.2.9 · · ·
1.9.3 177.40377 22.402250 · · · · · · 1.3.9 · · ·
1.10.1 177.39809 22.395856 · · · · · · · · · · · ·
1.10.2 177.39997 22.396708 · · · 36.2 · · · · · ·
1.10.3 177.40380 22.402183 · · · 36.3 · · · · · ·
1.11.2 177.40010 22.396661 · · · · · · 1.2.3 · · ·
1.11.3 177.40377 22.402047 · · · · · · 1.3.3 · · ·
1.12.1 177.39716 22.395211 · · · · · · 1.1.14 · · ·
1.12.2 177.40032 22.396925 · · · · · · 1.2.14 · · ·
1.12.3 177.40360 22.401878 · · · · · · 1.3.14 · · ·
1.13.1 177.39697 22.396639 7 24.1 1.1.19 · · ·
1.13.2 177.39882 22.397711 7 24.2 1.2.19 · · ·
1.13.3 177.40329 22.402828 7 24.3 1.3.19 · · ·
1.13.4 177.39791 22.398433 7 24.4 1.4.19 · · ·
1.*13.6 177.39852 22.398061 · · · · · · · · · 3
1.14.1 177.39712 22.396725 6 25.1 1.1.7 · · ·
1.14.2 177.39878 22.397633 6 25.2 1.2.7 · · ·
10. 10 Treu et al. (2015)
Table 4 — Continued
ID R.A. (J2000) Decl. (J2000) ID Smith et al. (2009) ID Sharon et al. (2015) ID Diego et al. (2015) Notes
1.14.3 177.40338 22.402872 6 25.3 1.3.7 · · ·
1.14.4 177.39810 22.398256 · · · 25.4 1.4.7 · · ·
1.15.1 177.39717 22.396506 · · · 41.1 1.1.20 · · ·
1.15.2 177.39894 22.397514 · · · 41.2 1.2.20 · · ·
1.15.3 177.40344 22.402753 · · · 41.3 1.3.20 · · ·
1.16.1 177.39745 22.396400 4 26.1 1.1.6 · · ·
1.16.2 177.39915 22.397228 4 26.2 1.2.6 · · ·
1.16.3 177.40360 22.402656 4 26.3 1.3.6 · · ·
1.17.1 177.39815 22.396347 3 11.1 1.1.5 · · ·
1.17.2 177.39927 22.396831 3 11.2 1.2.5 · · ·
1.17.3 177.40384 22.402564 3 11.3 1.3.5 · · ·
1.18.1 177.39850 22.396100 · · · · · · 1.1.11 · · ·
1.18.2 177.39947 22.396592 · · · · · · 1.2.11 · · ·
1.18.3 177.40394 22.402408 · · · · · · 1.3.11 · · ·
1.19.1 177.39689 22.395761 · · · 21.1 1.1.17 · · ·
1.19.2 177.39954 22.397486 · · · 21.2 1.2.17 · · ·
1.19.3 177.40337 22.402292 · · · 21.3 1.3.17 · · ·
1.19.5 177.39997 22.397106 · · · 21.4 1.5.17 · · ·
1.20.1 177.39708 22.395728 · · · 27.1 1.1.16 · · ·
1.20.2 177.39963 22.397361 · · · · · · 1.2.16 · · ·
1.20.3 177.40353 22.402233 · · · 27.3 1.3.16 · · ·
1.20.5 177.40000 22.396981 · · · 27.2 1.5.16 · · ·
1.21.1 177.39694 22.395406 · · · · · · 1.1.18 · · ·
1.21.3 177.40341 22.402006 · · · · · · 1.3.18 · · ·
1.21.5 177.40018 22.397042 · · · · · · 1.5.18 · · ·
1.22.1 177.39677 22.395487 · · · · · · · · · · · ·
1.22.2 177.39968 22.397495 · · · · · · · · · · · ·
1.22.3 177.40328 22.402098 · · · · · · · · · · · ·
1.22.5 177.40008 22.397139 · · · · · · · · · · · ·
1.23.1 177.39672 22.395381 15 22.1 1.1.2 · · ·
1.23.2 177.39977 22.397497 15 22.2 1.2.2 · · ·
1.23.3 177.40324 22.402011 15 22.3 1.3.2 · · ·
1.23.5 177.40013 22.397200 · · · 22.2 1.5.2 · · ·
1.24.1 177.39650 22.395589 · · · 28.1 1.1.4 · · ·
1.24.2 177.39953 22.397753 · · · 28.2 1.2.4 · · ·
1.24.3 177.40301 22.402203 · · · 28.3 1.3.4 · · ·
1.25.1 177.39657 22.395933 · · · · · · 1.1.21 · · ·
1.25.3 177.40304 22.402456 · · · · · · 1.3.21 · · ·
1.27.1 177.39831 22.396285 · · · 37.1 · · · · · ·
1.27.2 177.39933 22.396725 · · · 37.2 · · · · · ·
1.26.1 177.39633 22.396011 · · · · · · 1.1.12 · · ·
1.26.3 177.40283 22.402600 · · · · · · 1.3.12 · · ·
1.28.1 177.39860 22.396166 · · · 38.1 · · · · · ·
1.28.2 177.39942 22.396559 · · · 38.2 · · · · · ·
1.29.1 177.39858 22.395860 · · · 39.1 · · · · · ·
1.29.2 177.39976 22.396490 · · · 39.2 · · · · · ·
1.30.1 177.39817 22.395465 · · · 35.1 · · · · · ·
1.30.2 177.39801 22.395230 · · · 35.2 · · · · · ·
1.30.3 177.39730 22.395364 · · · 35.3 · · · · · ·
1.30.4 177.39788 22.395721 · · · 35.4 · · · · · ·
SN1 177.39823 22.395631 · · · 30.1 1.1.3a · · ·
SN2 177.39772 22.395783 · · · 30.2 1.1.3b · · ·
SN3 177.39737 22.395539 · · · 30.3 1.1.3c · · ·
SN4 177.39781 22.395189 · · · 30.4 1.1.3d · · ·
Note. — Coordinates and ID notations of emission knots in
the multiply-imaged host of SN Refsdal, at z = 1.488. The labels
in previous publications are indicated. New identifications were
made by C.G., K.S., and J.D. Each modeling team used a mod-
ified version or subset of the list above, with coordinates of each
knots varying slightly between modelers. Nevertheless, there is
consensus among the modelers on the identification and mapping
of the di↵erent features between the multiple images of the same
source.
1 Images 1.1, 1.2, 1.3, 1.5 were labeled by Zitrin & Broadhurst
(2009) as 1.2, 1.3, 1.1, 1.4, respectively. The labels of other knots
were not given in that publication.
2 This knot was identified as a counter image of the bulge of the
galaxy by Zitrin & Broadhurst (2009), but rejected by Smith et al.
(2009). As in the paper by Sharon & Johnson (2015), the model-
ers consensus is that this knot is likely at least a partial image of
the bulge.
3 Image 1.13.6 is predicted by some models as counter image of
1.13, but its identification is not confident enough to be used as
constraint.
11. MACS1149 Forecasts 11
4. BRIEF DESCRIPTION OF MODELING TECHNIQUES
AND THEIR INPUTS
For convenience of the reader, in this section we give
a brief description of each of the modeling techniques
compared in this work (summarized briefly in Table 4).
We note that the five models span a range of very dif-
ferent assumptions. Three of the teams (Grillo et al.,
Oguri et al., Sharon et al.) used an approach based on
modeling the mass distribution with a set of physically
motivated components, described each by a small num-
ber of parameters, representing the galaxies in the cluster
and the overall cluster halo. We refer to these models as
“simply-parametrized”. One of the approaches (Diego et
al.) describes the mass distribution with a larger num-
ber of components. The components are not associated
with any specific physical object and are used as build-
ing blocks, allowing for significant flexibility, balanced by
regularization. We refer to this model as “free-form”30
.
The fifth approach (Zitrin et al.), is based on the as-
sumption that light approximately traces mass, and the
mass components are built by smoothing and rescaling
the observed surface brightness of the cluster members.
We refer to this approach as “light-traces-mass”. All the
models considered here are single-plane lens models. As
we will discuss in Section 6, each type of model uses a
di↵erent approach to account for the e↵ects of structure
along the line of sight, and to break the mass sheet degen-
eracy. All model outputs will be made available through
the HFF website after the acceptance of the individual
modeling papers.
Table 5
Summary of models
Short name Team Type RMS Images
Die-a Diego et al. Free-form 0.78 gold+sil
Gri-g Grillo et al. Simply-param 0.26 gold
Ogu-g Oguri et al. Simply-param 0.43 gold
Ogu-a Oguri et al. Simply-param 0.31 all
Sha-g Sharon et al. Simply-param 0.16 gold
Sha-a Sharon et al. Simply-param 0.19 gold+sil
Zit-g Zitrin et al. Light-tr-mass 1.3 gold
Note. — For each model we provide a short name as well as
basic features and inputs. The column RMS lists the r.m.s. scatter
of the observed vs predicted image positions in arcseconds.
We note that members of our team have developed
another complementary “free-form” approach, based on
modeling the potential in pixels on an adaptive grid
(Bradaˇc et al. 2004b, 2009). However, given the pixel-
lated nature of the reconstruction and the need to com-
pute numerical derivatives and interpolate from noisy
pixels in order to compute time delays and magnifica-
tion at the location of ‘Refsdal’, we did not expect this
method to be competitive for this specific application.
Therefore in the interest of time we did not construct
this model. A pre-HFF model of MACSJ1149.5+2223
30 These models are sometimes described incorrectly as “non-
parametric”, even though they typically have more parameters
than the so-called parametric models.
using this approach is available through the HFF web-
site and will be updated in the future.
When appropriate, we also describe additional sets of
constraints used by each modeler.
4.1. Diego et al.
A full description of the modeling technique used by
this team (J.D., T.B.) and the various improvements im-
plemented in the code can be found in the literature
(Diego et al. 2005, 2007; Sendra et al. 2014; Diego et al.
2015). Here is a brief summary of the basic steps.
4.1.1. Definition of the mass model
The algorithm (WSLAP+) relies on a division of the
mass distribution in the lens plane into two components.
The first is compact and associated with the member
galaxies (mostly red ellipticals). The second is di↵use
and distributed as a superposition of Gaussians on a reg-
ular (or adaptive) grid. In this specific case, a grid of
512 ⇥ 512 pixels 0.00
1875 on a side was used. For the
compact component, the mass associated with the galax-
ies is assumed to be proportional to their luminosity.
If all the galaxies are assumed to have the same mass-
to-light (M/L) ratio, the compact component (galaxies)
contributes with just one (Ng = 1) extra free-parameter
wich corresponds to the correction that needs to be ap-
plied to the fiducial M/L ratio. In some particular cases,
some galaxies (like the BCG or massive galaxies very
close to an arclet) are allowed to have their own M/L ra-
tio adding additional free-parameters to the lens model
but typically no more than a few (Ng ⇠ O(1)). For this
component associated with the galaxies, the total mass
is assumed to follow either a Navarro et al. (1997, here-
after NFW) profile (with a fixed concentration, and scale
radius scaling with the fiducial halo mass) or be propor-
tional to the observed surface brightness. For this work
the team adopted Ng = 2 or Ng = 3. The case Ng = 2
considers one central brightest cluster galaxy (BCG) and
the elliptical galaxy near image 1.2 to have the same M/L
ratio, while the remaining galaxies have a di↵erent one.
In the case Ng = 3, the BCG and the galaxy near image
1.2 have each their own M/L ratio, and the remaining
galaxies are assumed to have a third independent value.
In all cases, it is important to emphasize that the mem-
ber galaxy between the 4 observed images of ‘Refsdal’
was not allowed to have its own independent M/L ratio.
This results in a model that is not as accurate on the
smallest scales around this galaxy as other models that
allow this galaxy to vary.
The di↵use, or ‘soft’, component, is described by as
many free parameters as grid (or cell) points. This num-
ber (Nc) varies but is typically between a few hundred
to one thousand (Nc ⇠ O(100)-O(1000)) depending on
the resolution and/or use of the adaptive grid. In addi-
tion to the free-parameters describing the lens model, the
problem includes as unknowns the original positions of
the lensed galaxies in the source plane. For the clusters
included in the HFF program the number of background
sources, Ns, is typically a few tens (Ns ⇠ O(10)), each
contributing with two unknowns ( x and y). All the
unknowns are then combined into a single array X with
Nx elements (Nx ⇠ O(1000)).
4.1.2. Definition of the inputs
12. 12 Treu et al. (2015)
The inputs are the pixel position of the strongly lensed
galaxies (not just the centroids) for all the multiple im-
ages listed in Tables 3 and 4. In the case of elongated arcs
near the critical curves with no features, the entire arc
is mapped and included as a constraint. If the arclets
have individual features, these can be incorporated as
semi-independent constraints but with the added condi-
tion that they need to form the same source in the source
plane. The following inputs are added to the default set
of image and knots centers listed in Section 3:
1. Shape of the arclets. This is particularly useful for
long elongated arcs (with no counter images) which
lie in the regime between the weak and strong lens-
ing. These arcs are still useful constraints that add
valuable information beyond the Einstein radius.
2. Shape and morphology of arcs. By including this
information one can account (at least partially) for
the magnification at a given position.
3. Resolved features in individual systems. This new
addition to the code is motivated by the host galaxy
of ‘Refsdal’ where multiple features can be identi-
fied in the di↵erent counter images. In addition,
the counter image in the North, when re-lensed,
o↵ers a robust picture of the original source mor-
phology (size, shape, orientation). This informa-
tion acts as an anchor, constraining the range of
possible solutions.
Weak lensing shear measurements can also be used
as input to the inference. For the particular case of
MACSJ1149.5+2223 the weak lensing measurements are
not used, to ensure homogeneity with the other methods.
4.1.3. Description of the inference process and error
estimation
The array of best fit parameters X, is obtained after
solving the system of linear equations
⇥ = X (1)
where the No observations (strong lensing, weak lensing,
time delays) are included in the array ⇥ and the matrix
is known and has dimension No ⇥ (Nc + Ng + 2Ns).
In practice, X is obtained by solving the set of linear
equations described in Eq. 1 via a fast bi-conjugate al-
gorithm, or inverted with a singular value decomposition
(after setting a threshold for the eigenvalues) or solved
with a more robust but slower quadratic algorithm. The
quadratic algorithm is the preferred method as it imposes
the physical constraint that the solution X must be pos-
itive. This eliminates unphysical solutions with negative
masses and reduces the space of possible solutions. Like
in the case of the bi-conjugate gradient, the quadratic
programming algorithm solves the system of linear equa-
tions by finding the minimum of the associated quadratic
function. Errors in the solution are derived by minimiz-
ing the quadratic function multiple times, after varying
the initial conditions of the minimization process, and/or
varying the grid configuration.
4.2. Grillo et al.
The software used by this team (C.G., S.H.S., A.H.,
P.R., W.K., I.B., A.M., G.B.C.) is Glee (Suyu &
Halkola 2010; Suyu et al. 2012). The strong lensing
analysis performed here follows very closely the one pre-
sented by Grillo et al. (2015) for another HFF tar-
get, i.e. MACSJ0416.1 2403. Cosmological applica-
tions of Glee can be found in Suyu et al. (2013, 2014)
and further details on the strong lensing modeling of
MACSJ1149.5+2223 are provided in a dedicated paper
(Grillo et al. 2015, in preparation).
4.2.1. Definition of the mass model
Di↵erent mass models have been explored for this
galaxy cluster, but only the best-fitting one is discussed
here. The projected dimensionless total surface mass
density of each of the 306 cluster members within the
WFC3 field of view of the CLASH observations is mod-
eled as a dual pseudoisothermal elliptical mass distribu-
tion (dPIE; El´ıasd´ottir et al. 2007) with vanishing ellip-
ticity and core radius. The galaxy luminosity values in
the F160W band are used to assign the relative weights to
their total mass profile. The galaxy total mass-to-light
ratio is scaled with luminosity as MT/L ⇠ L0.2
, thus
mimicking the so-called tilt of the Fundamental Plane.
The values of axis ratio, position angle, e↵ective velocity
dispersion and truncation radius of the two cluster mem-
bers closest in projection to the central and southern im-
ages of the ‘Refsdal’ host are left free. To complete the
total mass distribution of the galaxy cluster, three addi-
tional mass components are added to describe the clus-
ter dark matter halo on physical scales larger than those
typical of the individual cluster members. These cluster
halo components are parametrized as two-dimensional,
pseudo-isothermal elliptical mass profiles (PIEMD; Kas-
siola & Kovner 1993). No external shear or higher order
perturbations are included in the model. The number of
free parameters associated with the model of the cluster
total mass distribution is 28.
4.2.2. Definition of the inputs
The positions of the multiple images belonging to the
10 systems of the “gold” sample and to 18 knots of the
‘Refsdal’ host are the observables over which the values
of the model parameters are optimized. The adopted
positional uncertainty of each image is 0.00
065. The red-
shift values of the 7 spectroscopically confirmed “gold”
systems are fixed, while the remaining 3 systems are in-
cluded with a uniform prior on the value of Dds/Ds,
where Dds and Ds are the deflector-source and observer-
source angular diameter distances, respectively. In total,
88 observed image positions are used to reconstruct the
cluster total mass distribution.
4.2.3. Description of the inference process and error
estimation
The best-fitting, minimum- 2
model is obtained by
minimizing the distance between the observed and
model-predicted positions of the multiple images in the
lens plane. A minimum 2
value of 1441, correspond-
ing to a RMS o↵set between the image observed and
reconstructed positions of 0.00
26, is found. To sample the
posterior probability distribution function of the model
parameters, the image positional uncertainty is increased
13. MACS1149 Forecasts 13
until the value of the 2
is comparable to the number of
the degrees of freedom (89) and standard Markov chain
Monte Carlo (MCMC) methods are used. The quanti-
ties shown in Figures 9 to 12 are for the model-predicted
images of ‘Refsdal’ and are obtained from 100 di↵erent
models extracted from an MCMC chain with 106
samples
and an acceptance rate of approximately 0.13.
4.3. Oguri et al.
4.3.1. Definition of the mass model
This team (M.O., M.I., R.K.) uses the public soft-
ware glafic (Oguri 2010). This “simply-parametrized”
method assumes that the lens potential consists of a
small number of components describing dark halos, clus-
ter member galaxies, and perturbations in the lens po-
tential. The dark halo components are assumed to follow
the elliptical NFW mass density profile. In contrast, the
elliptical pseudo-Ja↵e profile is adopted to describe the
mass distribution of cluster member galaxies. In order to
reduce the number of free parameters, the velocity dis-
persion and the truncation radius rcut for each galaxy
are assumed to scale with the (F814W-band) luminosity
of the galaxy as / L1/4
and rcut / L⌘
with ⌘ being a
free parameter. In addition, the second (external shear)
and third order perturbations are included in order to
account for asymmetry of the overall lens potential. In-
terested readers are referred to Oguri (2010, 2015), Oguri
et al. (2012, 2013), and Ishigaki et al. (2015) for more
detailed descriptions and examples of cluster mass mod-
eling with glafic. Additional details are given in a ded-
icated paper (Kawamata et al. 2015, in preparation).
4.3.2. Definition of the inputs
The positions of multiple images and knots listed in
Section 3 are used as constraints. Image 1.5 was not
used as a constraint. To accurately recover the position
of SN ‘Refsdal’, di↵erent positional uncertainties are as-
sumed for di↵erent multiple images. Specifically, while
the positional uncertainty of 0.00
4 in the image plane is as-
sumed for most of multiple images, smaller positional un-
certainties of 0.00
05 and 0.00
2 are assumed for SN ‘Refsdal’
and knots of the SN host galaxy, respectively (see also
Oguri 2015). When spectroscopic redshifts are available,
their redshifts are fixed to the spectroscopic redshifts.
Otherwise source redshifts are treated as model param-
eters and are optimized simultaneously with the other
model parameters. For a subsample of multiple image
systems for which photometric redshift estimates are se-
cure and accurate, a conservative Gaussian prior with the
dispersion of z = 0.5 for the source redshift is added.
While glafic allows one to include other types of obser-
vational constraints, such as flux ratios, time delays, and
weak lensing shear measurements, those constraints are
not used in the mass modeling of MACSJ1149.5+2223.
4.3.3. Description of the inference process and error
estimation
The best-fit model is obtained simply by minimizing
2
. The so-called source plane 2
minimization is used
for an e cient model optimization (see Appendix 2 of
Oguri 2010). A standard MCMC approach is used to es-
timate errors on model parameters and their covariance.
The predicted time delays and magnifications are com-
puted at the model-predicted positions. For each mass
model (chain) the best-fit source position of the SN is de-
rived. From that, the corresponding SN image positions
in the image plane (which can be slightly di↵erent from
observed SN positions) are obtained for that model, and
finally the time delays and magnifications of the images
are calculated.
4.4. Sharon et al.
The approach of this team (K.S., T.J.) was based
on the publicly available software Lenstool (Jullo et al.
2007). Lenstool is a “simply-parametrized” lens model-
ing code. In practice, the code assumes that the mass
distribution of the lens can be described by a combina-
tion of mass halos, each of them taking a functional form
whose properties are defined by a set of parameters. The
method assumes that mass generally follows light, and
assigns halos to individual galaxies that are identified as
cluster members. Cluster- or group-scale halos represent
the cluster mass components that are not directly re-
lated to galaxies. The number of cluster or group-scale
halos is determined by the modeler. Typically, the po-
sitions of the cluster scale halos are not fixed and are
left to be determined by the modeling algorithms. A
hybrid “simply-parametrized”/“free-form” approach has
also been implemented in Lenstool (Jullo & Kneib 2009),
where numerous halos are placed on a grid, representing
the overall cluster component. This hybrid method is
not implemented in this work.
4.4.1. Definition of the mass model
All the halos are represented by a PIEMD mass distri-
bution with density profile ⇢(r) defined as:
⇢(r) =
⇢0
(1 + r2/r2
core)(1 + r2/r2
cut)
. (2)
These halos are isothermal at intermediate radii, i.e., ⇢ /
r 2
at rcore . r . rcut, and have a flat core internal
to rcore. The transition between the di↵erent slopes is
smooth. 0 defines the overall normalization as a fiducial
velocity dispersion. In Lenstool, each PIEMD halo has
seven free parameters: centroid position x,y; ellipticity
e = (a2
b2
)/(a2
+ b2
) where a and b are the semi major
and minor axis, respectively; position angle ✓; and rcore,
rcut, 0 as defined above.
The selection of cluster member galaxies is described
in Section 3.3. In this model, 286 galaxies were selected
from the cluster member catalog, by a combination of
their luminosity and projected distance from the clus-
ter center, such that the deflection caused by an omitted
galaxy is much smaller than the typical uncertainty due
to unseen structure along the line of sight. This selec-
tion criterion results in removal of faint galaxies at the
outskirts of the cluster, and inclusion of all the galaxies
that pass the cluster-member selection in the core.
Cluster member galaxies are modeled as PIEMD as
well. Their positional parameters are fixed on their ob-
served properties as measured with SExtractor (Bertin &
Arnouts 1996) for x, y, e, and ✓. The other parameters,
rcore, rcut, and 0, are linked to their luminosity in the
F814W band through scaling relations (e.g., Limousin
et al. 2005) assuming a constant mass-to-light ratio for
14. 14 Treu et al. (2015)
all galaxies,
0 = ⇤
0
⇣ L
L⇤
⌘1/4
and rcut = r⇤
cut
⇣ L
L⇤
⌘1/2
. (3)
4.4.2. Definition of the inputs
The lensing constraints are the positions of multiple
images of each lensed source, plus those of the knots in
the host galaxy of ‘Refsdal’, as listed in Section 3. In
cases where the lensed image is extended or has substruc-
ture, the exact positions were selected to match similar
features within multiple images of the same galaxy with
each other thus obtaining more constraints, a better lo-
cal sampling of the lensing potential, and better handle
on the magnification, locally. Where available, spectro-
scopic redshifts are used as fixed constraints. For sources
with no spectroscopic redshift, the redshifts are consid-
ered as free parameters with photometric redshifts in-
forming their Bayesian priors. The uncertainties of the
photometric redshifts are relaxed in order to allow for
outliers. We present two models here: Sha-g uses as con-
straints the ‘gold’ sample of multiply-imaged galaxies,
and Sha-a uses ‘gold’, ‘silver’, and secure arcs outside the
MUSE field of view, to allow a better coverage of lensing
evidence in the outskirts of the cluster and in particular
to constrain the sub halos around MACSJ1149.5+2223.
4.4.3. Description of the inference process and error
estimation
The parameters of each halo are allowed to vary un-
der Bayesian priors, and the parameter space is explored
in a n MCMC process to identify the set of parameters
that provide the best fit. The quality of the lens model
is measured either in the source plane or in the image
plane. The latter requires significantly longer computa-
tion time. In source plane minimization, the source posi-
tions of all the images of each set are computed, by ray-
tracing the image plane positions through the lens model
to the source plane. The best-fit model is the one that
results in the smallest scatter in the source positions of
multiple images of the same source. In image-plane min-
imization, the model-predicted counter images of each of
the multiple images of the same source is computed. This
results in a set of predicted images near the observed po-
sitions. The best-fit model is the one that minimizes the
scatter among these image-plane positions. The MCMC
sampling of the parameter space is used to estimate the
statistical uncertainties that are inherent to the model-
ing algorithm. In order to estimate the uncertainties on
the magnification and time delay magnification, poten-
tial maps are generated from sets of parameters from the
MCMC chain that represent 1- in the parameter space.
4.5. Zitrin et al.
4.5.1. Definition of the mass model
The method used by this team (A.Z.) is a Light Traces
Mass (LTM) method, so that both the galaxies and the
dark matter follow the light distribution. The method is
described in detail by Zitrin et al. (2009, 2013) and is in-
spired by the LTM assumptions outlined by Broadhurst
et al. (2005). The model consists of two main compo-
nents. The first component is a mass map of the clus-
ter galaxies, chosen by following the red sequence. Each
galaxy is represented with a power-law surface mass den-
sity distribution, where the surface density is propor-
tional to its surface brightness. The power-law is a free
parameter of the model and is iterated for (all galax-
ies are forced to have the same exponent). The second
component is a smooth dark matter map, obtained by
smoothing (with a Spline polynomial or with a Gaussian
kernel) the first component, i.e. the superposed red se-
quence galaxy mass distribution. The smoothing degree
is the second free parameter of the model. The two com-
ponents are then added with a relative weight which whis
is a free parameter, along with the overall normalization.
A two-component external shear can be then added to
add flexibility and generate ellipticity in the magnifica-
tion map. Lastly, individual galaxies can be assigned
with free masses to be optimized by the minimization
procedure, to allow more degrees of freedom deviating
form the initial imposed LTM. This procedure has been
shown to be very e↵ective in locating multiple images in
many clusters (e.g., Zitrin et al. 2009, 2012b, 2013, 2015)
even without any multiple images initially used as in-
put (Zitrin et al. 2012a). Most of the multiple images in
MACSJ1149.5+2223 that were found by Zitrin & Broad-
hurst (2009) and Zheng et al. (2012), were identified with
this method.
4.5.2. Definition of the inputs
All sets of multiple images in the gold list were used
except system 14. Most knots were used except those
in the fifth radial BCG image. All systems listed with
spec-z (aside for system 5) were kept fixed at that red-
shift while all other gold systems were left to be freely
optimized with a uniform flat prior. Image position un-
certainties were adopted to be 0.00
5, aside for the four SN
images for which 0.00
15 was used.
4.5.3. Description of the inference process and error
estimation
The best fit solution and errors are obtained via con-
verged MCMC chains.
5. COMPARISON OF LENS MODELS
In this section we carry out a comparison of the 7 mod-
els, focusing specifically on the quantities that are rele-
vant for ‘Refsdal’. We start in Section 5.1 by presenting
the two-dimensional maps of convergence, magnification
and time delay, for a deflector at the redshift of the clus-
ter and a source at the redshift of ‘Refsdal’ (z = 1.488; we
note that assuming z = 1.491, the redshift published by
Smith et al. (2009), would not have made any significant
di↵erence). Then, in Section 5.2, we compare quantita-
tively the predicted time delays and magnification ratios
of the known images with their mesaured values. Finally,
in Section 5.3 we present the forecast for the future (and
past) SN image. All the lens models predict the appear-
ance of an image of the SN in the two other images of
the host galaxy. In the following sections, we refer to
the predicted SN in image 1.2 of the host galaxy as SX,
and the one in image 1.3 of the host as SY, following the
labeling of previous publications.
5.1. Convergence, magnification and time delay maps
Figure 4 shows the convergence (i.e., surface mass den-
sity in units of the lensing critical density) maps. There
15. MACS1149 Forecasts 15
Figure 4. Comparing the mass distributions for the models, labeled as in Table 4. Convergence is computed relative to the critical density
with the deflector at the redshift of the cluster and the source at the redshift of the supernova. The cirles identify the positions of the
observed and predicted images of Refsdal and those of the multiple images of its host galaxy. The top four panels are models including
only the gold sample of images as constraints.
are striking qualitative di↵erences. The Zit-g map is sig-
nificantly rounder than the others. The Die-a map has
significantly more structure, notably two overdensities
near SY/1.3 and at the bottom right of the map. These
features were to be expected based on the assumptions
used by their methods. The Grillo, Oguri, Sharon con-
vergence maps are the most qualitatively similar. This
is perhaps unsurprising since the three codes are based
on fairly similar assumptions.
Magnification maps are shown in Fig. 5. The regions
of extreme magnification are qualitatively similar, even
though, similarly to the convergence maps, the Zit-g
model is overall rounder, while the Die-a model has more
structure.
The time delay surfaces are shown at three zoom lev-
els to highlight di↵erent features. Fig. 6 shows the global
topology of the time delay surfaces, which is very similar
for all models, with minima near 1.1 and SY/1.3 and a
saddle point near SX/1.2. As was the case with conver-
gence and magnification, the Zit-g and Die-a time delays
surfaces are rounder and have more structure, respec-
tively, than those produced by the other models.
Zooming in the region of SX/1.2 and 1.1 in Fig. 7 re-
veals more di↵erences. The locations of the minimum
near SN ‘Refsdal’ and of the saddle point near 1.2 are
significantly di↵erent for the Zit-g model, seemingly as a
result of the di↵erent contribution of the bright galaxy
to the NW of 1.2.
A further zoom in the region of the known images is
shown in Figure 8. The time delay surface contour levels
are shown in step of 10 days to highlight the behaviour
relevant for the cross configuration. Whereas the “simply
16. 16 Treu et al. (2015)
Figure 5. As Figure 4 for magnification.
parametrized” models are topologically very similar to
each other, the Die-a and Zit-g models are qualitatively
di↵erent. The time delay surface is shifted upwards -
probably as a result of the nearby perturber highlighted
in the previous paragraph. We stress that all the mod-
els here are global models, developed to reproduce the
cluster potential on larger scale. Hence, local di↵erences
should be expected, even though of course they are par-
ticularly important in this case.
5.2. Comparing model predictions with measured time
delays and magnification ratios
Before proceeding with a quantitative comparison, we
emphasize once again that the uncertainties discussed in
this Section only include statistical uncertainties. Fur-
thermore, in the comparison we neglect for computa-
tional reasons the covariance between the uncertainties
in time delay and between those in magnification. Sys-
tematic uncertainties will be discussed in Section 6.
Figure 9 compares the measured time delays with those
predicted by the models for the cross configuration. We
stress that the measurements were not used in the con-
struction of the models (or known to the modelers) and
therefore they can be considered an independent test of
the models. The time delay between S2 and S1 (and to
some extent that between S3 and S1) is very short and
in fact not all the models agree on the ordering of the
two images. The time delay between S4 and S1 is longer
and better behaved, with all the models agreeing on the
order of the images and with the measured value within
the uncertainties. Overall the models are in reasonable
agreement with the measurements, even though formally
some of them are in statistical tension. This indicates
that the uncertainties for some of the parametric models
are underestimated.
Interestingly, the models appear to predict rather ac-
curately the observed magnification ratios (Fig. 10), even
though these quantitites should be more sensitive to sys-
17. MACS1149 Forecasts 17
Figure 6. As Figure 4 for time delay surfaces. The dashed boxes mark the location of the zoom-ins shown in Figure 7. Contour levels
show the time delay from -12 to 12 years in increments of 3 years, relative to S1. For the Sha-a and Sha-g models the time delay surfaces
were only calculated in the region shown. Negative levels are marked by dashed contours. The gray-scale background image shows the
HFF F140W epoch2 version 1.0 mosaic.
tematic uncertainties arising from milli-lensing and mi-
crolensing e↵ects than time delays.
Overall, the Zit-g model stands apart from the rest,
predicting significantly di↵erent time delays and magni-
fication ratios, and larger uncertainties. This qualita-
tive di↵erence is consistent with the di↵erent topology
of the time-delay surface highlighted in the previous sec-
tion. Quantitatively, however, the Zit-g model predic-
tions are in broad agreement with the measurements if
one considers the 95% credible interval. Collectively, the
“simply-parametrized” models seem to predict smaller
uncertainties than the others, especially the Ogu-g and
Ogu-a ones. This is expected, considering that they have
less flexibility than the free form model. What is surpris-
ing, however, is that they also obtain the smaller r.m.s.
residual scatter in the predicted vs observed image po-
sitions (Table 4). The Zit-g light traces mass model is
perhaps the least flexible, in the sense that it cannot
account for systematic variations in the projected mass-
to-light ratio. This appears to be reflected in its over-
all largest r.m.s. residual scatter. When comparing the
Die-a to the Zit-g model, we note that the former uses
18. 18 Treu et al. (2015)
Figure 7. The time delay surface details in the region marked in Figure 6. The dashed boxes mark the location of the zoom-ins shown
in Figure 8. Contour levels show the time delay from -5 to 5 years in increments of 0.5 years, relative to S1. Negative levels are marked by
dashed contours. The gray-scale background image shows the HFF F140W epoch2 version 1.0 mosaic.
significantly more constraints than the latter. This may
explain why, even though Die-a is in principle more flexi-
ble, it ends up estimating generally smaller uncertainties
than Zit-g.
5.3. Forecasts for ‘Refsdal’: peak appearance and
brightness
Figure 11 compares the prediction for the next appear-
ance of SN ‘Refsdal’, near image 1.2 of the spiral galaxy
(hereafter SX/1.2). All the models considered here pre-
dict the image to peak between the end of 2015 and the
first half of 2016. We note that S1 was first discovered six
months before its peak with F160W AB magnitude ⇠25.5
(Kelly et al. 2015), and peaked at about F160W⇠24.5 AB
(Kelly et al. 2015, in preparation; Strolger et al. 2015, in
preparation). Image SX/1.2 is predicted to be approxi-
mately 1/3 as bright as image S1 (Figure 12), so it should
be approximately ⇠26.7 six months before peak and 25.7
at peak. No image is detected in the vicinity of SY/1.3
in data taken with HST up until MACSJ1149.5+2223
became unobservable at the end of July, allowing us to
rule out predicted peak times until January 2016.
Remarkably, the models are in excellent mutual agree-
ment regarding the next appearance of ‘Refsdal’. All the
19. MACS1149 Forecasts 19
Figure 8. The time delay surface details in the region marked in Figure 7. Contour levels show the time delay from -50 to 50 days in
increments of 10 days, relative to S1. Negative levels are marked by dashed contours. The gray-scale background image shows the HFF
F140W epoch2 version 1.0 mosaic.
predictions agree on the first trimester of 2016 as the
most likely date of the peak. Sha-a is the only one that
predicts a slightly fainter flux with a magnification ratio
(0.19+0.01
0.04) as opposed to the ⇠1/3 value predicted by
the other models. Interestingly, Zit-g has the largest un-
certainty on time delay, but not on magnification ratio.
As in the case of the cross configuration, the “simply-
parametrized” models yield the smallest uncertainties.
Unfortunately, the model-based estimates of the past
appearance of ‘Refsdal’ cannot be tested by observations.
The image near 1.3 (herafter SY/1.3) is estimated to have
been significantly fainter than S1, and thus undetectable
from the ground, at a time when WFC3-IR was not avail-
able. The images of MACSJ1149.5+2223 taken in the
optical with ACS in April 2004 (GO: 9722, PI: Ebeling;
3- limit F814W AB = 27.0) are not su ciently deep
to set any significant constraints, considering the peak
brightness of S1 in F814W was approximately ⇠27, and
we expect SY/1.3 to be 0.75 to 2 magnitudes fainter.
As a purely theoretical exercise it is interesting to notice
that the time delay varies dramatically between models,
di↵ering by almost 10 years between the Zit-g and the
Sha-a, Sha-g and Die-a models. Remarkably, and sim-
ilarly to what was seen for the cross configuration, the
20. 20 Treu et al. (2015)
Figure 9. Observed (solid vertical line with dotted lines repre-
sents the measurement and uncertainty by Kelly et al.; dashed
vertical line represents the measurement by Strolger et al.) and
predicted (points with error bars) time delays for the images in the
cross configuration, relative to S1. Uncertainties represent the 68%
confidence interval.
Figure 10. Observed (lines as in Figure 9) and predicted (points
with error bars) magnification ratios (absolute values) for the im-
ages in the cross configuration, relative to S1.
magnifications are in significantly better agreement.
6. DISCUSSION
In this section we briefly discuss our results, first by re-
capitulating the limitations of our analysis (Section 6.1),
and then by comparing them with previous work (Sec-
tion 6.2).
Figure 11. Predicted time delays for the more distant images,
relative to S1. The top scale gives the expected date of the peak
brightness of the image - with an uncertainty of ±20 days given by
the uncertainty on the date of the peak of the observed images. The
hatched region is ruled out by past observations with the Hubble
Space Telescope.
Figure 12. Predicted magnification ratios (absolute values) for
the more distant images, relative to S1.
6.1. Limitation of the blind test and of the models
SN ‘Refsdal’ gives us a unique opportunity to test our
models blindly. However, in order to draw the appropri-
ate conclusions from this test, we need to be aware of the
limitations of both the test and the models.
The first limitation to keep in mind, is that this test
21. MACS1149 Forecasts 21
is very specific. We are e↵ectively testing point-like pre-
dictions of the lensing potential and its derivatives. Sim-
ilarly to the case of SN ‘Tomas’ (Rodney et al. 2015), it
is very hard to generalize the results of this test even to
the strong lensing area shown in our maps. More global
metrics should be used to infer a more global assessment
of the quality of the models. An example of such metric
is the r.m.s. scatter between the image positions given
in Table 4, even though of course even this metric does
not capture all the features of a model. For example the
r.m.s. does not capture how well the model reproduces
time delays and magnifications, in addition to positions,
and one could imaging trading one for the other.
It is also important to remind ourselves that whereas
the magnification and time delays at specific points may
vary significantly between models, other quantities that
are more relevant for statistical use of clusters as cos-
mic telescopes, such as the area in the source plane,
are much more stable (e.g., Wang et al. 2015). And,
of course, other quantities such as colors and line ra-
tios, are not a↵ected at all by gravitational lensing. It
would be interesting to find ways to carry out true ob-
servational tests of more global predictions of lens mod-
els. One way to achieve this would be to carry out tests
similar to those a↵orded by ‘Tomas’ and ‘Refsdal’ on a
large sample of clusters. Another possibility could be to
reach su ciently deep that the statistical properties of
the background sources (e.g. the luminosity function) are
measured with su cient precision and su ciently small
cosmic variance to allow for meaningful tests of model
uncertainties. Alternatively, tests against simulated data
are certainly informative (e.g. Meneghetti et al. 2015,
in preparation), although their results should also be in-
terpreted with great care, as they depend crucially on
the fidelity of the simulated data and the cross-talk be-
tween methods used to simulate the data and those used
to carry out the inference.
The second limitation to keep in mind is that the un-
certainties listed in this paper are purely statistical in
nature. As for the case of image positions – where the
r.m.s. scatter is typically larger than the astrometric pre-
cision of the image positions themselves (consistent with
the fact that there are residual systematics in cluster lens
modeling due to known e↵ects such as substructure, e.g.,
Bradaˇc et al. 2009) – we should not expect the time de-
lays and magnifications to be perfectly reproduced by the
models either. The spread between the di↵erent model
predictions gives us an idea of the so-called model un-
certainties, even though unfortunately they cannot be
considered an exact measurement. The spread could be
exaggerated by inappropriate assumptions in some of the
models, or underestimated if common assumptions are
unjustified.
As already mentioned in the introduction, other poten-
tial sources of uncertainty are related to the mass sheet
degeneracy and its generalizations (Falco et al. 1985;
Schneider & Sluse 2013, 2014), the e↵ects of structure
along the line of sight (Dalal et al. 2005), and multi-
plane lensing (Schneider 2014; McCully et al. 2014). All
the models considered here are single plane lens models.
They break the mass sheet degeneracy by assuming that
the surface mass density profile goes to zero at infinity
with a specific radial dependency.
On the scale of the known images of ‘Refsdal’, the mea-
sured time delays and magnification ratios give us a way
to estimate these residual uncertainties. The reasonably
good agreement between the model prediction and mea-
surements shows that these (systematic) ‘unknown un-
knowns’ are not dominant with the respect to the (statis-
tical) ‘known unknowns’. However, since the agreement
is not perfect, we conclude that the ‘unknown unknowns’
are not negligible either. We can perhaps use the ex-
perience gathered in the study of time delays of lensed
quasars to estimate the amplitude of the line of sight un-
certainties. On scales similar to that of the known images
of ‘Refsdal’ they are believed to be up to ⇠ 10% before
corrections for galaxies not in clusters (Suyu et al. 2010;
Greene et al. 2013; Collett et al. 2013; Suyu et al. 2014).
In numerical simulations the line of sight e↵ects appear
to increase with the measured overdensity of galaxies
(Greene et al. 2013), so it is possible that they are larger
for an overdense region like that of MACSJ1149.5+2223.
On galaxy scales, breaking the mass-sheet degeneracy
using stellar kinematics and physically motivated galaxy
models appears to produce results consistent with resid-
ual uncertainties of the order of a few per cent (Suyu
et al. 2014). On cluster scales, the degeneracy is partly
broken by the use of multiple images at di↵erent redshifts
(e.g., Bradaˇc et al. 2004a). However, in the absence of
non-lensing data, we cannot rule out that the residual
mass-sheet degeneracy is the dominant source of system-
atic uncertainty. Assessing the uncertainties related to
multiplane e↵ects would require knowledge of the mass
distribution in three-dimensions and is beyond the scope
of the present work. Thus multiplane lensing cannot be
ruled out as a significant source of systematic uncertainty
for the prediction of the time delay and magnification ra-
tios of the known images of ‘Refsdal’. As far as the future
image of ‘Refsdal’ is concerned, future observations will
tell us how much our uncertainties are underestimated
due to unknown systematics.
Finally, we remind the reader that although for this
analysis we kept fixed the cosmological parameters, they
are a (subdominant) source of uncertainty. To first order,
the time delay distance is proportional to the Hubble
Constant, so there is at least a 3% systematic uncertainty
(Riess et al. 2011; Freedman et al. 2012) on our predicted
time delays (and substantially more when considering
all the other parameters, depending on assumptions and
priors; Suyu et al. 2013, 2014).
6.2. Comparison with previous models
We can get a quantitative sense of the improvement of
the mass models as a result of the new data by comparing
how the prediction of the time delay and magnification
ratios have changed for the teams who had previously
publish predictions.
6.2.1. Previous models by members of our team
The Zit-g model updates the models developed by A.Z.
for the ’Refsdal’ discovery paper (Kelly et al. 2015). The
Zit-g model supercedes the estimates of time delays and
magnifications given in the original paper by providing
predictions as well as quantitative uncertainties.
The update of the Oguri (2015) model presented here
changes the time delays for S2, S3, S4, SX, SY from
9.2, 5.2, 22.5, 357, -6193 days to 8.7 ± 0.7, 5.1 ± 0.5,