A highly magnetized twin-jet base pinpoints a supermassive black holeSérgio Sacani
Supermassive black holes (SMBH) are essential for the production of jets in radio-loud active galactic nuclei (AGN). Theoretical
models based on (Blandford & Znajek 1977, MNRAS, 179, 433) extract the rotational energy from a Kerr black hole, which could
be the case for NGC1052, to launch these jets. This requires magnetic fields on the order of 103 G to 104 G. We imaged the vicinity
of the SMBH of the AGN NGC1052 with the Global Millimetre VLBI Array and found a bright and compact central feature that is
smaller than 1.9 light days (100 Schwarzschild radii) in radius. Interpreting this as a blend of the unresolved jet bases, we derive the
magnetic field at 1 Schwarzschild radius to lie between 200 G and 8:3 104 G consistent with Blandford & Znajek models.
PROBING FOR EVIDENCE OF PLUMES ON EUROPA WITH HST/STISSérgio Sacani
Roth et al. (2014a) reported evidence for plumes of water venting from a southern high latitude
region on Europa – spectroscopic detection of off-limb line emission from the dissociation
products of water. Here, we present Hubble Space Telescope (HST) direct images of Europa in
the far ultraviolet (FUV) as it transited the smooth face of Jupiter, in order to measure absorption
from gas or aerosols beyond the Europa limb. Out of ten observations we found three in which
plume activity could be implicated. Two show statistically significant features at latitudes similar
to Roth et al., and the third, at a more equatorial location. We consider potential systematic
effects that might influence the statistical analysis and create artifacts, and are unable to find any
that can definitively explain the features, although there are reasons to be cautious. If the
apparent absorption features are real, the magnitude of implied outgassing is similar to that of the
Roth et al. feature, however the apparent activity appears more frequently in our data.
Galaxy dynamics and the mass density of the universeSérgio Sacani
Dynamical evidence accumulated over the
past 20 years has convinced astronomers that luminous matter
in a spiral galaxy constitutes no more than 10% of the mass of
a galaxy. An additional 90% is inferred by its gravitational
effect on luminous material. Here I review recent observations
concerning the distribution of luminous and nonluminous
matter in the Milky Way, in galaxies, and in galaxy clusters.
Observations of neutral hydrogen disks, some extending in
radius several times the optical disk, confirm that a massive
dark halo is a major component of virtually every spiral. A
recent surprise has been the discovery that stellar and gas
motions in ellipticals are enormously complex. To date, only for
a few spheroidal galaxies do the velocities extend far enough to
probe the outer mass distribution. But the diverse kinematics
of inner cores, peripheral to deducing the overall mass distribution,
offer additional evidence that ellipticals have acquired
gas-rich systems after initial formation. Dynamical results are
consistent with a low-density universe, in which the required
dark matter could be baryonic. On smallest scales of galaxies
[10 kiloparsec (kpc); H. = 50 kmsec'lmegaparsec'11 the
luminous matter constitutes only 1% of the closure density. On
scales greater than binary galaxies (i.e., .100 kpc) all systems
indicate a density -10% of the closure density, a density
consistent with the low baryon density in the universe. If
large-scale motions in the universe require a higher mass
density, these motions would constitute the first dynamical
evidence for nonbaryonic matter in a universe of higher
density.
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.
A highly magnetized twin-jet base pinpoints a supermassive black holeSérgio Sacani
Supermassive black holes (SMBH) are essential for the production of jets in radio-loud active galactic nuclei (AGN). Theoretical
models based on (Blandford & Znajek 1977, MNRAS, 179, 433) extract the rotational energy from a Kerr black hole, which could
be the case for NGC1052, to launch these jets. This requires magnetic fields on the order of 103 G to 104 G. We imaged the vicinity
of the SMBH of the AGN NGC1052 with the Global Millimetre VLBI Array and found a bright and compact central feature that is
smaller than 1.9 light days (100 Schwarzschild radii) in radius. Interpreting this as a blend of the unresolved jet bases, we derive the
magnetic field at 1 Schwarzschild radius to lie between 200 G and 8:3 104 G consistent with Blandford & Znajek models.
PROBING FOR EVIDENCE OF PLUMES ON EUROPA WITH HST/STISSérgio Sacani
Roth et al. (2014a) reported evidence for plumes of water venting from a southern high latitude
region on Europa – spectroscopic detection of off-limb line emission from the dissociation
products of water. Here, we present Hubble Space Telescope (HST) direct images of Europa in
the far ultraviolet (FUV) as it transited the smooth face of Jupiter, in order to measure absorption
from gas or aerosols beyond the Europa limb. Out of ten observations we found three in which
plume activity could be implicated. Two show statistically significant features at latitudes similar
to Roth et al., and the third, at a more equatorial location. We consider potential systematic
effects that might influence the statistical analysis and create artifacts, and are unable to find any
that can definitively explain the features, although there are reasons to be cautious. If the
apparent absorption features are real, the magnitude of implied outgassing is similar to that of the
Roth et al. feature, however the apparent activity appears more frequently in our data.
Galaxy dynamics and the mass density of the universeSérgio Sacani
Dynamical evidence accumulated over the
past 20 years has convinced astronomers that luminous matter
in a spiral galaxy constitutes no more than 10% of the mass of
a galaxy. An additional 90% is inferred by its gravitational
effect on luminous material. Here I review recent observations
concerning the distribution of luminous and nonluminous
matter in the Milky Way, in galaxies, and in galaxy clusters.
Observations of neutral hydrogen disks, some extending in
radius several times the optical disk, confirm that a massive
dark halo is a major component of virtually every spiral. A
recent surprise has been the discovery that stellar and gas
motions in ellipticals are enormously complex. To date, only for
a few spheroidal galaxies do the velocities extend far enough to
probe the outer mass distribution. But the diverse kinematics
of inner cores, peripheral to deducing the overall mass distribution,
offer additional evidence that ellipticals have acquired
gas-rich systems after initial formation. Dynamical results are
consistent with a low-density universe, in which the required
dark matter could be baryonic. On smallest scales of galaxies
[10 kiloparsec (kpc); H. = 50 kmsec'lmegaparsec'11 the
luminous matter constitutes only 1% of the closure density. On
scales greater than binary galaxies (i.e., .100 kpc) all systems
indicate a density -10% of the closure density, a density
consistent with the low baryon density in the universe. If
large-scale motions in the universe require a higher mass
density, these motions would constitute the first dynamical
evidence for nonbaryonic matter in a universe of higher
density.
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.
The ASTRODEEP Frontier Fields catalogues II. Photometric redshifts and rest f...Sérgio Sacani
Aims. We present the first public release of photometric redshifts, galaxy rest frame properties and associated magnification values
in the cluster and parallel pointings of the first two Frontier Fields, Abell-2744 and MACS-J0416. The released catalogues aim to
provide a reference for future investigations of extragalactic populations in these legacy fields: from lensed high-redshift galaxies to
cluster members themselves.
Methods.We exploit a multiwavelength catalogue, ranging from Hubble Space Telescope (HST) to ground-based K and Spitzer IRAC,
which is specifically designed to enable detection and measurement of accurate fluxes in crowded cluster regions. The multiband
information is used to derive photometric redshifts and physical properties of sources detected either in the H-band image alone, or
from a stack of four WFC3 bands. To minimize systematics, median photometric redshifts are assembled from six dierent approaches
to photo-z estimates. Their reliability is assessed through a comparison with available spectroscopic samples. State-of-the-art lensing
models are used to derive magnification values on an object-by-object basis by taking into account sources positions and redshifts.
Results. We show that photometric redshifts reach a remarkable 3–5% accuracy. After accounting for magnification, the H-band
number counts are found to be in agreement at bright magnitudes with number counts from the CANDELS fields, while extending
the presently available samples to galaxies that, intrinsically, are as faint as H 32 33, thanks to strong gravitational lensing. The
Frontier Fields allow the galaxy stellar mass distribution to be probed, depending on magnification, at 0.5–1.5 dex lower masses with
respect to extragalactic wide fields, including sources at Mstar 107–108 M at z > 5. Similarly, they allow the detection of objects
with intrinsic star formation rates (SFRs) >1 dex lower than in the CANDELS fields reaching 0.1–1 M=yr at z 6–10.
A giant galaxy in the young Universe with a massive ringSérgio Sacani
In the local (redshift z ≈ 0) Universe, collisional ring galaxies make up only ~0.01% of galaxies1 and are formed by head-on galactic collisions that trigger radially propagating density waves2–4. These striking systems provide key snapshots for dissecting galactic disks and are studied extensively in the local Universe5–9. However, not much is known about distant (z > 0.1) collisional rings10–14. Here we present a detailed study of a ring galaxy at a look-back time of 10.8 Gyr (z = 2.19). Compared with our Milky Way, this galaxy has a similar stellar mass, but has a stellar half-light radius that is 1.5–2.2 times larger and is forming stars 50 times faster. The extended, dif- fuse stellar light outside the star-forming ring, combined with a radial velocity on the ring and an intruder galaxy nearby, provides evidence for this galaxy hosting a collisional ring. If the ring is secularly evolved15,16, the implied large bar in a giant disk would be inconsistent with the current understand- ing of the earliest formation of barred spirals17–21. Contrary to previous predictions10–12, this work suggests that massive col- lisional rings were as rare 11 Gyr ago as they are today. Our discovery offers a unique pathway for studying density waves in young galaxies, as well as constraining the cosmic evolution of spiral disks and galaxy groups.
Observation of Bose–Einstein condensates in an Earth-orbiting research labSérgio Sacani
Quantum mechanics governs the microscopic world, where low mass and momentum
reveal a natural wave–particle duality. Magnifying quantum behaviour to
macroscopic scales is a major strength of the technique of cooling and trapping
atomic gases, in which low momentum is engineered through extremely low
temperatures. Advances in this feld have achieved such precise control over atomic
systems that gravity, often negligible when considering individual atoms, has
emerged as a substantial obstacle. In particular, although weaker trapping felds
would allow access to lower temperatures1,2
, gravity empties atom traps that are too
weak. Additionally, inertial sensors based on cold atoms could reach better
sensitivities if the free-fall time of the atoms after release from the trap could be made
longer3
. Planetary orbit, specifcally the condition of perpetual free-fall, ofers to lift
cold-atom studies beyond such terrestrial limitations. Here we report production of
rubidium Bose–Einstein condensates (BECs) in an Earth-orbiting research laboratory,
the Cold Atom Lab. We observe subnanokelvin BECs in weak trapping potentials with
free-expansion times extending beyond one second, providing an initial
demonstration of the advantages ofered by a microgravity environment for
cold-atom experiments and verifying the successful operation of this facility. With
routine BEC production, continuing operations will support long-term investigations
of trap topologies unique to microgravity4,5
, atom-laser sources6
, few-body physics7,8
and pathfnding techniques for atom-wave interferometry9–12
A rare case of FR I interaction with a hot X-ray bridge in the A2384 galaxy c...Sérgio Sacani
Clusters of varying mass ratios can merge and the process significantly disturbs
the cluster environments and alters their global properties. Active radio galaxies are
another phenomenon that can also affect cluster environments. Radio jets can interact
with the intra-cluster medium (ICM) and locally affect its properties. Abell 2384
(hereafter A2384) is a unique system that has a dense, hot X-ray filament or bridge
connecting the two unequal mass clusters A2384(N) and A2384(S). The analysis of its
morphology suggests that A2384 is a post-merger system where A2384(S) has already
interacted with the A2384(N), and as a result hot gas has been stripped over a ∼ 1
Mpc region between the two bodies. We have obtained its 325 MHz GMRT data,
and we detected a peculiar FR I type radio galaxy which is a part of the A2384(S).
One of its radio lobes interacts with the hot X-ray bridge and pushes the hot gas in
the opposite direction. This results in displacement in the bridge close to A2384(S).
Based on Chandra and XMM-Newton X-ray observations, we notice a temperature and
entropy enhancement at the radio lobe-X-ray plasma interaction site, which further
suggests that the radio lobe is changing thermal plasma properties. We have also
studied the radio properties of the FR I radio galaxy, and found that the size and
radio luminosity of the interacting north lobe of the FR I galaxy are lower than those
of the accompanying south lobe.
Observed glacier and volatile distribution on Pluto from atmosphere–topograph...Sérgio Sacani
Pluto has a variety of surface frosts and landforms as well as a
complex atmosphere1. There is ongoing geological activity related
to the massive Sputnik Planum glacier, mostly made of nitrogen (N2)
ice mixed with solid carbon monoxide and methane2, covering the
4-kilometre-deep, 1,000-kilometre-wide basin of Sputnik Planum1,3
near the anti-Charon point. The glacier has been suggested to arise
from a source region connected to the deep interior, or from a sink
collecting the volatiles released planetwide1. Thin deposits of N2
frost, however, were also detected at mid-northern latitudes and
methane ice was observed to cover most of Pluto except for the
darker, frost-free equatorial regions2. Here we report numerical
simulations of the evolution of N2, methane and carbon monoxide
on Pluto over thousands of years. The model predicts N2 ice
accumulation in the deepest low-latitude basin and the threefold
increase in atmospheric pressure that has been observed to occur
since 19884–6. This points to atmospheric–topographic processes as
the origin of Sputnik Planum’s N2 glacier. The same simulations also
reproduce the observed quantities of volatiles in the atmosphere and
show frosts of methane, and sometimes N2, that seasonally cover the
mid- and high latitudes, explaining the bright northern polar cap
reported in the 1990s7,8 and the observed ice distribution in 20152.
The model also predicts that most of these seasonal frosts should
disappear in the next decade.
Spitzer Observations of the Predicted Eddington Flare from Blazar OJ 287Sérgio Sacani
Binary black hole (BH) central engine description for the unique blazar OJ 287 predicted that the
next secondary BH impact-induced bremsstrahlung flare should peak on 2019 July 31. This prediction
was based on detailed general relativistic modeling of the secondary BH trajectory around the primary
BH and its accretion disk. The expected flare was termed the Eddington flare to commemorate the
centennial celebrations of now-famous solar eclipse observations to test general relativity by Sir Arthur
Corresponding author: Lankeswar Dey
lankeswar.dey@tifr.res.in
arXiv:2004.13392v1 [astro-ph.HE] 28 Apr 2020
2 Laine et al.
Eddington. We analyze the multi-epoch Spitzer observations of the expected flare between 2019 July
31 and 2019 September 6, as well as baseline observations during 2019 February–March. Observed
Spitzer flux density variations during the predicted outburst time display a strong similarity with
the observed optical pericenter flare from OJ 287 during 2007 September. The predicted flare appears
comparable to the 2007 flare after subtracting the expected higher base-level Spitzer flux densities at
3.55 and 4.49 µm compared to the optical R-band. Comparing the 2019 and 2007 outburst lightcurves
and the previously calculated predictions, we find that the Eddington flare arrived within 4 hours of
the predicted time. Our Spitzer observations are well consistent with the presence of a nano-Hertz
gravitational wave emitting spinning massive binary BH that inspirals along a general relativistic
eccentric orbit in OJ 287. These multi-epoch Spitzer observations provide a parametric constraint
on the celebrated BH no-hair theorem.
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.
Imaging the dust_sublimation_front_of_a_circumbinary_diskSérgio Sacani
Aims. We present the first near-IR milli-arcsecond-scale image of a post-AGB binary that is surrounded by hot circumbinary dust.
Methods. A very rich interferometric data set in six spectral channels was acquired of IRAS 08544-4431 with the new RAPID camera
on the PIONIER beam combiner at the Very Large Telescope Interferometer (VLTI). A broadband image in the H-band was reconstructed
by combining the data of all spectral channels using the SPARCO method.
Results. We spatially separate all the building blocks of the IRAS 08544-4431 system in our milliarcsecond-resolution image. Our
dissection reveals a dust sublimation front that is strikingly similar to that expected in early-stage protoplanetary disks, as well as an
unexpected flux signal of 4% from the secondary star. The energy output from this companion indicates the presence of a compact
circum-companion accretion disk, which is likely the origin of the fast outflow detected in H.
Conclusions. Our image provides the most detailed view into the heart of a dusty circumstellar disk to date. Our results demonstrate
that binary evolution processes and circumstellar disk evolution can be studied in detail in space and over time.
On some structural_features_of_the_metagalaxySérgio Sacani
Progress in a group of investigations designed
to discover some of the structural details in individual galaxies and in the
Metagalaxy is reported in the following pages.
(a) The first section is concerned with the distribution of cluster-type
Cepheids in high galactic latitude. To the 169 already known in latitudes,
greater than or equal to ± 20o
, the systematic variable star programme carried
on at Harvard has added 312, mostly fainter than magnitude 13-0. With
allowance for absorption and for uncertainties yet remaining in the mean
absolute magnitude of these stars, the thickness of the Milky Way, so far
as this type of star is concerned, is not less than twenty-five kiloparsecs ;
he extent of the Milky Way in its own plane, by the same criterion, is more
than thirty kiloparsecs, perhaps much more.
(b) The extent of the Milky Way in the anti-centre quadrant is considered
on the basis of classical and cluster-type Cepheids ; provisionally
it is found that the galactic system reaches to a distance of at least ten
kiloparsecs in longitude 150o
.
(r) More than six hundred new variables have been found in the Large
Magellanic Cloud and measured for position, ranges and median magnitudes ;
the frequency of periods is not unlike that for the classical Cepheids in the
galactic system ; the light curves also are comparable in all details. The
Magellanic Cepheids, like the galactic classical Cepheids, are concentrated
in regions of high star-density.
(d) Further study of the period-luminosity relation in the Large Magellanic
Cloud permits its revision and strengthening for the Cepheids of
highest absolute magnitude. An observed deviation from the relation
that had previously been found for the Small Cloud is probably to be
attributed to scale error in the magnitude system. No seriously disturbing
The discovery of_lensed_radio_and_x-ray_sources_behind_the_frontier_fields_cl...Sérgio Sacani
We report on high-resolution JVLA and Chandra observations of the Hubble Space Telescope (HST) Frontier Cluster
MACSJ0717.5+3745. MACSJ0717.5+3745 offers the largest contiguous magnified area of any known cluster,
making it a promising target to search for lensed radio and X-ray sources. With the high-resolution 1.0–6.5 GHz
JVLA imaging in A and B configuration, we detect a total of 51 compact radio sources within the area covered by the
HST imaging. Within this sample, we find sevenlensed sources with amplification factors larger than two. None of
these sources are identified as multiply lensed. Based on the radio luminosities, the majority of these sources are
likely star-forming galaxies with star-formation rates (SFRs) of 10–50 M: yr−1 located at 1 1 z 1 2. Two of the
lensed radio sources are also detected in the Chandra image of the cluster. These two sources are likely active galactic
nuclei, given their 2–10 keV X-ray luminosities of ∼1043–44 erg s−1. From the derived radio luminosity function, we
find evidence for an increase in the number density of radio sources at 0.6 z 2.0, compared to a z 0.3 sample.
Our observations indicate that deep radio imaging of lensing clusters can be used to study star-forming galaxies, with
SFRs as low as ∼10Me yr−1, at the peak of cosmic star formation history.
Detection of solar_like_oscillations_in_relies_of_the_milk_way_asteroseismolo...Sérgio Sacani
Asteroseismic constraints on K giants make it possible to infer radii, masses and ages of tens
of thousands of field stars. Tests against independent estimates of these properties are however
scarce, especially in the metal-poor regime. Here, we report the detection of solar-like
oscillations in 8 stars belonging to the red-giant branch and red-horizontal branch of the globular
cluster M4. The detections were made in photometric observations from the K2 Mission
during its Campaign 2. Making use of independent constraints on the distance, we estimate
masses of the 8 stars by utilising different combinations of seismic and non-seismic inputs.
When introducing a correction to the Δν scaling relation as suggested by stellar models, for
RGB stars we find excellent agreement with the expected masses from isochrone fitting, and
with a distance modulus derived using independent methods. The offset with respect to independent
masses is lower, or comparable with, the uncertainties on the average RGB mass
(4 − 10%, depending on the combination of constraints used). Our results lend confidence to
asteroseismic masses in the metal poor regime. We note that a larger sample will be needed
to allow more stringent tests to be made of systematic uncertainties in all the observables
(both seismic and non-seismic), and to explore the properties of RHB stars, and of different
populations in the cluster.
A thirty-four billion solar mass black hole in SMSS J2157–3602, the most lumi...Sérgio Sacani
From near-infrared spectroscopic measurements of the Mg II emission line doublet, we estimate the black hole (BH) mass of the quasar, SMSS J215728.21–360215.1, as being (3.4 ± 0.6) × 1010 M⊙ and refine the redshift of the quasar to be z = 4.692. SMSS J2157 is the most luminous known quasar, with a 3000 Å luminosity of (4.7 ± 0.5) × 1047 erg s−1 and an estimated bolometric luminosity of 1.6 × 1048 erg s−1 , yet its Eddington ratio is only ∼0.4. Thus, the high luminosity of this quasar is a consequence of its extremely large BH – one of the most massive BHs at z > 4.
Flaring from the_supermassive_black_hole_in_mrk335_studied_with_swift_and_nustarSérgio Sacani
Os comportamentos estranhos e desconcertantes dos buracos negros tornam-se cada dia menos misteriosos, com as novas observações feitas com as missões Swift e NuSTAR da NASA. Os dois telescópios espaciais registraram um buraco negro supermassivo no meio de uma gigantesca explosão de luz de raio-X, ajudando os astrônomos a tentarem resolver um grande quebra-cabeça: Como os buracos negros supermassivos emitem flares?
Os resultados sugerem que os buracos negros supermassivos emitem flares de raios-X, quando suas coroas circundantes, fontes de partículas extremamente energéticas, são atiradas ou lançadas para fora dos buracos negros.
“Essa é a primeira vez que nós somos capazes de linkar o lançamento da coroa com uma flare”, disse Dan Wilkins, da Universidade de Saint Mary em Halifax, no Canadá e principal autor do artigo que descreve os resultados na revista Monthly Notices of The Royal Astronomical Society. “Isso nos ajudará a entender como os buracos negros supermassivos alimentam alguns dos objetos mais brilhantes do universo”.
Os buracos negros supermassivos não emitem luz por si só, mas eles as vezes são circundados por discos de material quente e brilhante. A gravidade do buraco negro puxa o gás ao redor, aquecendo esse material e fazendo com que ele brilhe com diferentes tipos de luz. Outra fonte da radiação perto do buraco negro é a coroa. As coroas são feitas de partículas altamente energéticas que geram luz de raio-X, mas os detalhes sobre sua aparência, ou como elas se formam, ainda não são claros.
Validation of twelve_small_kepler_transiting_planets_in_the_habitable_zoneSérgio Sacani
Artigo descreve a análise dos mais novos exoplanetas descobertos pela missão Kepler, incluindo o Kepler-438b, o exoplaneta mais parecido com a Terra já descoberto até o momento.
The ASTRODEEP Frontier Fields catalogues II. Photometric redshifts and rest f...Sérgio Sacani
Aims. We present the first public release of photometric redshifts, galaxy rest frame properties and associated magnification values
in the cluster and parallel pointings of the first two Frontier Fields, Abell-2744 and MACS-J0416. The released catalogues aim to
provide a reference for future investigations of extragalactic populations in these legacy fields: from lensed high-redshift galaxies to
cluster members themselves.
Methods.We exploit a multiwavelength catalogue, ranging from Hubble Space Telescope (HST) to ground-based K and Spitzer IRAC,
which is specifically designed to enable detection and measurement of accurate fluxes in crowded cluster regions. The multiband
information is used to derive photometric redshifts and physical properties of sources detected either in the H-band image alone, or
from a stack of four WFC3 bands. To minimize systematics, median photometric redshifts are assembled from six dierent approaches
to photo-z estimates. Their reliability is assessed through a comparison with available spectroscopic samples. State-of-the-art lensing
models are used to derive magnification values on an object-by-object basis by taking into account sources positions and redshifts.
Results. We show that photometric redshifts reach a remarkable 3–5% accuracy. After accounting for magnification, the H-band
number counts are found to be in agreement at bright magnitudes with number counts from the CANDELS fields, while extending
the presently available samples to galaxies that, intrinsically, are as faint as H 32 33, thanks to strong gravitational lensing. The
Frontier Fields allow the galaxy stellar mass distribution to be probed, depending on magnification, at 0.5–1.5 dex lower masses with
respect to extragalactic wide fields, including sources at Mstar 107–108 M at z > 5. Similarly, they allow the detection of objects
with intrinsic star formation rates (SFRs) >1 dex lower than in the CANDELS fields reaching 0.1–1 M=yr at z 6–10.
A giant galaxy in the young Universe with a massive ringSérgio Sacani
In the local (redshift z ≈ 0) Universe, collisional ring galaxies make up only ~0.01% of galaxies1 and are formed by head-on galactic collisions that trigger radially propagating density waves2–4. These striking systems provide key snapshots for dissecting galactic disks and are studied extensively in the local Universe5–9. However, not much is known about distant (z > 0.1) collisional rings10–14. Here we present a detailed study of a ring galaxy at a look-back time of 10.8 Gyr (z = 2.19). Compared with our Milky Way, this galaxy has a similar stellar mass, but has a stellar half-light radius that is 1.5–2.2 times larger and is forming stars 50 times faster. The extended, dif- fuse stellar light outside the star-forming ring, combined with a radial velocity on the ring and an intruder galaxy nearby, provides evidence for this galaxy hosting a collisional ring. If the ring is secularly evolved15,16, the implied large bar in a giant disk would be inconsistent with the current understand- ing of the earliest formation of barred spirals17–21. Contrary to previous predictions10–12, this work suggests that massive col- lisional rings were as rare 11 Gyr ago as they are today. Our discovery offers a unique pathway for studying density waves in young galaxies, as well as constraining the cosmic evolution of spiral disks and galaxy groups.
Observation of Bose–Einstein condensates in an Earth-orbiting research labSérgio Sacani
Quantum mechanics governs the microscopic world, where low mass and momentum
reveal a natural wave–particle duality. Magnifying quantum behaviour to
macroscopic scales is a major strength of the technique of cooling and trapping
atomic gases, in which low momentum is engineered through extremely low
temperatures. Advances in this feld have achieved such precise control over atomic
systems that gravity, often negligible when considering individual atoms, has
emerged as a substantial obstacle. In particular, although weaker trapping felds
would allow access to lower temperatures1,2
, gravity empties atom traps that are too
weak. Additionally, inertial sensors based on cold atoms could reach better
sensitivities if the free-fall time of the atoms after release from the trap could be made
longer3
. Planetary orbit, specifcally the condition of perpetual free-fall, ofers to lift
cold-atom studies beyond such terrestrial limitations. Here we report production of
rubidium Bose–Einstein condensates (BECs) in an Earth-orbiting research laboratory,
the Cold Atom Lab. We observe subnanokelvin BECs in weak trapping potentials with
free-expansion times extending beyond one second, providing an initial
demonstration of the advantages ofered by a microgravity environment for
cold-atom experiments and verifying the successful operation of this facility. With
routine BEC production, continuing operations will support long-term investigations
of trap topologies unique to microgravity4,5
, atom-laser sources6
, few-body physics7,8
and pathfnding techniques for atom-wave interferometry9–12
A rare case of FR I interaction with a hot X-ray bridge in the A2384 galaxy c...Sérgio Sacani
Clusters of varying mass ratios can merge and the process significantly disturbs
the cluster environments and alters their global properties. Active radio galaxies are
another phenomenon that can also affect cluster environments. Radio jets can interact
with the intra-cluster medium (ICM) and locally affect its properties. Abell 2384
(hereafter A2384) is a unique system that has a dense, hot X-ray filament or bridge
connecting the two unequal mass clusters A2384(N) and A2384(S). The analysis of its
morphology suggests that A2384 is a post-merger system where A2384(S) has already
interacted with the A2384(N), and as a result hot gas has been stripped over a ∼ 1
Mpc region between the two bodies. We have obtained its 325 MHz GMRT data,
and we detected a peculiar FR I type radio galaxy which is a part of the A2384(S).
One of its radio lobes interacts with the hot X-ray bridge and pushes the hot gas in
the opposite direction. This results in displacement in the bridge close to A2384(S).
Based on Chandra and XMM-Newton X-ray observations, we notice a temperature and
entropy enhancement at the radio lobe-X-ray plasma interaction site, which further
suggests that the radio lobe is changing thermal plasma properties. We have also
studied the radio properties of the FR I radio galaxy, and found that the size and
radio luminosity of the interacting north lobe of the FR I galaxy are lower than those
of the accompanying south lobe.
Observed glacier and volatile distribution on Pluto from atmosphere–topograph...Sérgio Sacani
Pluto has a variety of surface frosts and landforms as well as a
complex atmosphere1. There is ongoing geological activity related
to the massive Sputnik Planum glacier, mostly made of nitrogen (N2)
ice mixed with solid carbon monoxide and methane2, covering the
4-kilometre-deep, 1,000-kilometre-wide basin of Sputnik Planum1,3
near the anti-Charon point. The glacier has been suggested to arise
from a source region connected to the deep interior, or from a sink
collecting the volatiles released planetwide1. Thin deposits of N2
frost, however, were also detected at mid-northern latitudes and
methane ice was observed to cover most of Pluto except for the
darker, frost-free equatorial regions2. Here we report numerical
simulations of the evolution of N2, methane and carbon monoxide
on Pluto over thousands of years. The model predicts N2 ice
accumulation in the deepest low-latitude basin and the threefold
increase in atmospheric pressure that has been observed to occur
since 19884–6. This points to atmospheric–topographic processes as
the origin of Sputnik Planum’s N2 glacier. The same simulations also
reproduce the observed quantities of volatiles in the atmosphere and
show frosts of methane, and sometimes N2, that seasonally cover the
mid- and high latitudes, explaining the bright northern polar cap
reported in the 1990s7,8 and the observed ice distribution in 20152.
The model also predicts that most of these seasonal frosts should
disappear in the next decade.
Spitzer Observations of the Predicted Eddington Flare from Blazar OJ 287Sérgio Sacani
Binary black hole (BH) central engine description for the unique blazar OJ 287 predicted that the
next secondary BH impact-induced bremsstrahlung flare should peak on 2019 July 31. This prediction
was based on detailed general relativistic modeling of the secondary BH trajectory around the primary
BH and its accretion disk. The expected flare was termed the Eddington flare to commemorate the
centennial celebrations of now-famous solar eclipse observations to test general relativity by Sir Arthur
Corresponding author: Lankeswar Dey
lankeswar.dey@tifr.res.in
arXiv:2004.13392v1 [astro-ph.HE] 28 Apr 2020
2 Laine et al.
Eddington. We analyze the multi-epoch Spitzer observations of the expected flare between 2019 July
31 and 2019 September 6, as well as baseline observations during 2019 February–March. Observed
Spitzer flux density variations during the predicted outburst time display a strong similarity with
the observed optical pericenter flare from OJ 287 during 2007 September. The predicted flare appears
comparable to the 2007 flare after subtracting the expected higher base-level Spitzer flux densities at
3.55 and 4.49 µm compared to the optical R-band. Comparing the 2019 and 2007 outburst lightcurves
and the previously calculated predictions, we find that the Eddington flare arrived within 4 hours of
the predicted time. Our Spitzer observations are well consistent with the presence of a nano-Hertz
gravitational wave emitting spinning massive binary BH that inspirals along a general relativistic
eccentric orbit in OJ 287. These multi-epoch Spitzer observations provide a parametric constraint
on the celebrated BH no-hair theorem.
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.
Imaging the dust_sublimation_front_of_a_circumbinary_diskSérgio Sacani
Aims. We present the first near-IR milli-arcsecond-scale image of a post-AGB binary that is surrounded by hot circumbinary dust.
Methods. A very rich interferometric data set in six spectral channels was acquired of IRAS 08544-4431 with the new RAPID camera
on the PIONIER beam combiner at the Very Large Telescope Interferometer (VLTI). A broadband image in the H-band was reconstructed
by combining the data of all spectral channels using the SPARCO method.
Results. We spatially separate all the building blocks of the IRAS 08544-4431 system in our milliarcsecond-resolution image. Our
dissection reveals a dust sublimation front that is strikingly similar to that expected in early-stage protoplanetary disks, as well as an
unexpected flux signal of 4% from the secondary star. The energy output from this companion indicates the presence of a compact
circum-companion accretion disk, which is likely the origin of the fast outflow detected in H.
Conclusions. Our image provides the most detailed view into the heart of a dusty circumstellar disk to date. Our results demonstrate
that binary evolution processes and circumstellar disk evolution can be studied in detail in space and over time.
On some structural_features_of_the_metagalaxySérgio Sacani
Progress in a group of investigations designed
to discover some of the structural details in individual galaxies and in the
Metagalaxy is reported in the following pages.
(a) The first section is concerned with the distribution of cluster-type
Cepheids in high galactic latitude. To the 169 already known in latitudes,
greater than or equal to ± 20o
, the systematic variable star programme carried
on at Harvard has added 312, mostly fainter than magnitude 13-0. With
allowance for absorption and for uncertainties yet remaining in the mean
absolute magnitude of these stars, the thickness of the Milky Way, so far
as this type of star is concerned, is not less than twenty-five kiloparsecs ;
he extent of the Milky Way in its own plane, by the same criterion, is more
than thirty kiloparsecs, perhaps much more.
(b) The extent of the Milky Way in the anti-centre quadrant is considered
on the basis of classical and cluster-type Cepheids ; provisionally
it is found that the galactic system reaches to a distance of at least ten
kiloparsecs in longitude 150o
.
(r) More than six hundred new variables have been found in the Large
Magellanic Cloud and measured for position, ranges and median magnitudes ;
the frequency of periods is not unlike that for the classical Cepheids in the
galactic system ; the light curves also are comparable in all details. The
Magellanic Cepheids, like the galactic classical Cepheids, are concentrated
in regions of high star-density.
(d) Further study of the period-luminosity relation in the Large Magellanic
Cloud permits its revision and strengthening for the Cepheids of
highest absolute magnitude. An observed deviation from the relation
that had previously been found for the Small Cloud is probably to be
attributed to scale error in the magnitude system. No seriously disturbing
The discovery of_lensed_radio_and_x-ray_sources_behind_the_frontier_fields_cl...Sérgio Sacani
We report on high-resolution JVLA and Chandra observations of the Hubble Space Telescope (HST) Frontier Cluster
MACSJ0717.5+3745. MACSJ0717.5+3745 offers the largest contiguous magnified area of any known cluster,
making it a promising target to search for lensed radio and X-ray sources. With the high-resolution 1.0–6.5 GHz
JVLA imaging in A and B configuration, we detect a total of 51 compact radio sources within the area covered by the
HST imaging. Within this sample, we find sevenlensed sources with amplification factors larger than two. None of
these sources are identified as multiply lensed. Based on the radio luminosities, the majority of these sources are
likely star-forming galaxies with star-formation rates (SFRs) of 10–50 M: yr−1 located at 1 1 z 1 2. Two of the
lensed radio sources are also detected in the Chandra image of the cluster. These two sources are likely active galactic
nuclei, given their 2–10 keV X-ray luminosities of ∼1043–44 erg s−1. From the derived radio luminosity function, we
find evidence for an increase in the number density of radio sources at 0.6 z 2.0, compared to a z 0.3 sample.
Our observations indicate that deep radio imaging of lensing clusters can be used to study star-forming galaxies, with
SFRs as low as ∼10Me yr−1, at the peak of cosmic star formation history.
Detection of solar_like_oscillations_in_relies_of_the_milk_way_asteroseismolo...Sérgio Sacani
Asteroseismic constraints on K giants make it possible to infer radii, masses and ages of tens
of thousands of field stars. Tests against independent estimates of these properties are however
scarce, especially in the metal-poor regime. Here, we report the detection of solar-like
oscillations in 8 stars belonging to the red-giant branch and red-horizontal branch of the globular
cluster M4. The detections were made in photometric observations from the K2 Mission
during its Campaign 2. Making use of independent constraints on the distance, we estimate
masses of the 8 stars by utilising different combinations of seismic and non-seismic inputs.
When introducing a correction to the Δν scaling relation as suggested by stellar models, for
RGB stars we find excellent agreement with the expected masses from isochrone fitting, and
with a distance modulus derived using independent methods. The offset with respect to independent
masses is lower, or comparable with, the uncertainties on the average RGB mass
(4 − 10%, depending on the combination of constraints used). Our results lend confidence to
asteroseismic masses in the metal poor regime. We note that a larger sample will be needed
to allow more stringent tests to be made of systematic uncertainties in all the observables
(both seismic and non-seismic), and to explore the properties of RHB stars, and of different
populations in the cluster.
A thirty-four billion solar mass black hole in SMSS J2157–3602, the most lumi...Sérgio Sacani
From near-infrared spectroscopic measurements of the Mg II emission line doublet, we estimate the black hole (BH) mass of the quasar, SMSS J215728.21–360215.1, as being (3.4 ± 0.6) × 1010 M⊙ and refine the redshift of the quasar to be z = 4.692. SMSS J2157 is the most luminous known quasar, with a 3000 Å luminosity of (4.7 ± 0.5) × 1047 erg s−1 and an estimated bolometric luminosity of 1.6 × 1048 erg s−1 , yet its Eddington ratio is only ∼0.4. Thus, the high luminosity of this quasar is a consequence of its extremely large BH – one of the most massive BHs at z > 4.
Flaring from the_supermassive_black_hole_in_mrk335_studied_with_swift_and_nustarSérgio Sacani
Os comportamentos estranhos e desconcertantes dos buracos negros tornam-se cada dia menos misteriosos, com as novas observações feitas com as missões Swift e NuSTAR da NASA. Os dois telescópios espaciais registraram um buraco negro supermassivo no meio de uma gigantesca explosão de luz de raio-X, ajudando os astrônomos a tentarem resolver um grande quebra-cabeça: Como os buracos negros supermassivos emitem flares?
Os resultados sugerem que os buracos negros supermassivos emitem flares de raios-X, quando suas coroas circundantes, fontes de partículas extremamente energéticas, são atiradas ou lançadas para fora dos buracos negros.
“Essa é a primeira vez que nós somos capazes de linkar o lançamento da coroa com uma flare”, disse Dan Wilkins, da Universidade de Saint Mary em Halifax, no Canadá e principal autor do artigo que descreve os resultados na revista Monthly Notices of The Royal Astronomical Society. “Isso nos ajudará a entender como os buracos negros supermassivos alimentam alguns dos objetos mais brilhantes do universo”.
Os buracos negros supermassivos não emitem luz por si só, mas eles as vezes são circundados por discos de material quente e brilhante. A gravidade do buraco negro puxa o gás ao redor, aquecendo esse material e fazendo com que ele brilhe com diferentes tipos de luz. Outra fonte da radiação perto do buraco negro é a coroa. As coroas são feitas de partículas altamente energéticas que geram luz de raio-X, mas os detalhes sobre sua aparência, ou como elas se formam, ainda não são claros.
Validation of twelve_small_kepler_transiting_planets_in_the_habitable_zoneSérgio Sacani
Artigo descreve a análise dos mais novos exoplanetas descobertos pela missão Kepler, incluindo o Kepler-438b, o exoplaneta mais parecido com a Terra já descoberto até o momento.
Artigo da Science Express apresentando os últimos resultados da sonda Rosetta que mostram que a água presente no cometa 67P/C-G tem uma razão de deutério/hidrogênio, três vezes maior do que aquela encontrada nos oceanos da Terra, isso faz com que volte com força total o debate sobre de onde a água dos nossos oceanos se originou.
Multi dimensional simulations_of_the_expanding_supernova_remnant_of_sn1987_aSérgio Sacani
Artigo descreve as mais novas simulações computacionais realizadas para se poder entender o funcionamento e a origem da remanescente de supernova SN1987A.
Um dos artigos da edição especial da revista Science, mostrando as alterações nas propriedades do cometa Churyumov-Gerasimenko, à medida que ele se aproxima do Sol.
Chandra deep observation_of_xdcpj004402033_a_massive_galaxy_cluster_at_z_1_5Sérgio Sacani
Artigo apresenta os resultados obtidos pelo Chandra ao medir com precisão a massa do mais massivo aglomerado de galáxias do universo distante, o Aglomerado Gioiello.
Artigo descreve a descoberta de um sistema de anéis 200 vezes maior do que o sistema de anéis de Saturno num exoplaneta orbitando a jovem estrela J1407
Probing the innermost_regions_of_agn_jets_and_their_magnetic_fields_with_radi...Sérgio Sacani
Desde 1974, observações feitas com o chamado Long Baseline Interferometry, ou VLBI, combinaram sinais de um objeto cósmico recebidos em diferentes rádio telescópios espalhados pelo globo para criar uma antena com o tamanho equivalente à maior separação entre elas. Isso fez com que fosse possível fazer imagens com uma nitidez sem precedentes, com uma resolução 1000 vezes melhor do que Hubble consegue na luz visível. Agora, uma equipe internacional de astrônomos quebrou todos os recordes combinando 15 rádio telescópios na Terra e a antena de rádio da missão RadioAstron, da agência espacial russa, na órbita da Terra. O trabalho, liderado pelo Instituto de Astrofísica de Andalucía, o IAA-CSIC, forneceu novas ideias sobre a natureza das galáxias ativas, onde um buraco negro extremamente massivo engole a matéria ao redor enquanto simultaneamente emite um par de jatos de partículas de alta energia e campos magnéticos a velocidades próximas da velocidade da luz.
Observações feitas no comprimento de onda das micro-ondas são essenciais para explorar esses jatos, já que os elétrons de alta energia se movendo em campos magnéticos são mais proficientes em produzir micro-ondas. Mas a maioria das galáxias ativas com jatos brilhantes estão a bilhões de anos-luz de distância da Terra, de modo que esses jatos são minúsculos no céu. Desse modo a alta resolução é essencial para observar esses jatos em ação e então revelar fenômenos como as ondas de choque e a turbulência que controla o quanto de luz é produzida num dado tempo. “Combinando pela primeira vez rádio telescópios na Terra com rádio telescópios no espaço, operando na máxima resolução, tem permitido que a nossa equipe crie uma antena que tem um tamanho equivalente a 8 vezes o diâmetro da Terra, correspondendo a 20 micro arcos de segundo”, disse José L; Gómez, o líder da equipe no Instituto de Astrofísica de Andalucía, IAA-CSIC.
Radio continum emission_of_35_edge_on_galaxies_observed_with_the_vlaSérgio Sacani
Usando um dos maiores rádio observatórios do mundo, o Very Large Array do National Radio Astronomy, um grupo de astrônomos descobriram que os halos ao redor dos discos das galáxias espirais são muito mais comuns do que se pensava anteriormente.
A equipe, dirigida pela Dra. Judith Irwin, da Universidade de Queens, em Kingston, ON, Canadá, observou 35 galáxias espirais próximas de lado, de 11 a 137 milhões de anos-luz de distância da Terra.
As galáxias espirais, como a nossa própria Via Láctea ou a famosa Galáxia de Andrômeda, possuem uma vasta maioria de suas estrelas, gás, e poeira num disco plano em rotação com braços espirais. A maior parte da luz e das ondas de rádio observadas com telescópios veem de objetos localizados nesse disco.
“Nós sabíamos antes que alguns halos existiam, mas, usando o poder total do VLA atualizado e o poder total de algumas técnicas de processamento de imagens, nós descobrimos que esses halos são muito mais comuns entre as galáxias espirais do que nós pensávamos antes”, explicou a Dra. Irwin.
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
Solving the Multimessenger Puzzle of the AGN-starburst Composite Galaxy NGC 1068Sérgio Sacani
Multiwavelength observations indicate that some starburst galaxies show a dominant nonthermal contribution from
their central region. These active galactic nuclei (AGN)-starburst composites are of special interest, as both
phenomena on their own are potential sources of highly energetic cosmic rays and associated γ-ray and neutrino
emission. In this work, a homogeneous, steady-state two-zone multimessenger model of the nonthermal emission
from the AGN corona as well as the circumnuclear starburst region is developed and subsequently applied to the
case of NGC 1068, which has recently shown some first indications of high-energy neutrino emission. Here, we
show that the entire spectrum of multimessenger data—from radio to γ-rays including the neutrino constraint—can
be described very well if both, starburst and AGN corona, are taken into account. Using only a single emission
region is not sufficient.
Inverse Compton cooling limits the brightness temperature of the radiating plasma to a maximum of
1011.5 K. Relativistic boosting can increase its observed value, but apparent brightness temperatures
much in excess of 1013 K are inaccessible using ground-based very long baseline interferometry (VLBI)
at any wavelength. We present observations of the quasar 3C 273, made with the space VLBI mission
RadioAstron on baselines up to 171,000 km, which directly reveal the presence of angular structure as
small as 26 µas (2.7 light months) and brightness temperature in excess of 1013 K. These measurements
challenge our understanding of the non-thermal continuum emission in the vicinity of supermassive
black holes and require a much higher Doppler factor than what is determined from jet apparent
kinematics.
Keywords: galaxies: active — galaxies: jets — radio continuum: galaxies — techniques: interferometric
— quasars: individual (3C 273)
The first X-ray look at SMSS J114447.77-430859.3: the most luminous quasar in...Sérgio Sacani
SMSS J114447.77-430859.3 (z = 0.83) has been identified in the SkyMapper Southern Survey as the most luminous quasar in
the last ∼ 9 Gyr . In this paper, we report on the eROSITA/Spectrum–Roentgen–Gamma (SRG) observations of the source from
the eROSITA All Sky Survey, along with presenting results from recent monitoring performed using Swift, XMM-Newton, and
NuSTAR. The source shows a clear variability by factors of ∼10 and ∼2.7 overtime-scales of a year and of a few days,respectively.
When fit with an absorbed power law plus high-energy cutoff, the X-ray spectra reveal a = 2.2 ± 0.2 and Ecut = 23+26
−5 keV
. Assuming Comptonization, we estimate a coronal optical depth and electron temperature of τ = 2.5 − 5.3 (5.2 − 8) and
kT = 8 − 18 (7.5 − 14) keV , respectively, for a slab (spherical) geometry. The broadband SED is successfully modelled by
assuming either a standard accretion disc illuminated by a central X-ray source, or a thin disc with a slim disc emissivity profile.
The former model results in a black hole mass estimate of the order of 1010 M , slightly higher than prior optical estimates;
meanwhile, the latter model suggests a lower mass. Both models suggest sub-Eddington accretion when assuming a spinning
black hole, and a compact (∼ 10 rg ) X-ray corona. The measured intrinsic column density and the Eddington ratio strongly
suggest the presence of an outflow driven by radiation pressure. This is also supported by variation of absorption by an order of
magnitude over the period of ∼ 900 d .
Polarized thermal emission from dust in a galaxy at red2 shift 2.6Sérgio Sacani
Magnetic fields are fundamental to the evolution of galaxies, playing a key role in the astro15 physics of the interstellar medium (ISM) and star formation. Large-scale ordered magnetic
(B) fields have been mapped in the Milky Way and nearby galaxies1, 2
16 , but it is not known
how early in the Universe such structures form3
17 . Here we report the detection of linearly po18 larized thermal emission from dust grains in a strongly lensed, intrinsically luminous galaxy
19 that is forming stars at a rate more than a thousand times that of the Milky Way at redshift
2.6, within 2.5 Gyr of the Big Bang4, 5
20 . The polarized emission arises from the alignment
of dust grains with the local magnetic field6, 7
21 . The median polarization fraction is of order
one per cent, similar to nearby spiral galaxies8
22 . Our observations support the presence of a
23 5 kiloparsec-scale ordered B-field with a strength of around 500µG or lower, orientated par24 allel to the molecular gas disc. This confirms that such structures can be rapidly formed in
25 galaxies, early in cosmic history.
Similar to Probing the fermi_bubbles_in_ultraviolet_absorption_spectroscopic_signature_of_the_milky_way (20)
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.
Efficient spin-up of Earth System Models usingsequence accelerationSérgio Sacani
Marine and terrestrial biogeochemical models are key components of the Earth System Models (ESMs) used toproject future environmental changes. However, their slow adjustment time also hinders effective use of ESMsbecause of the enormous computational resources required to integrate them to a pre-industrial equilibrium. Here,a solution to this "spin-up" problem based on "sequence acceleration", is shown to accelerate equilibration of state-of-the-art marine biogeochemical models by over an order of magnitude. The technique can be applied in a "blackbox" fashion to existing models. Even under the challenging spin-up protocols used for Intergovernmental Panelon Climate Change (IPCC) simulations, this algorithm is 5 times faster. Preliminary results suggest that terrestrialmodels can be similarly accelerated, enabling a quantification of major parametric uncertainties in ESMs, improvedestimates of metrics such as climate sensitivity, and higher model resolution than currently feasible.
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.
The increased availability of biomedical data, particularly in the public domain, offers the opportunity to better understand human health and to develop effective therapeutics for a wide range of unmet medical needs. However, data scientists remain stymied by the fact that data remain hard to find and to productively reuse because data and their metadata i) are wholly inaccessible, ii) are in non-standard or incompatible representations, iii) do not conform to community standards, and iv) have unclear or highly restricted terms and conditions that preclude legitimate reuse. These limitations require a rethink on data can be made machine and AI-ready - the key motivation behind the FAIR Guiding Principles. Concurrently, while recent efforts have explored the use of deep learning to fuse disparate data into predictive models for a wide range of biomedical applications, these models often fail even when the correct answer is already known, and fail to explain individual predictions in terms that data scientists can appreciate. These limitations suggest that new methods to produce practical artificial intelligence are still needed.
In this talk, I will discuss our work in (1) building an integrative knowledge infrastructure to prepare FAIR and "AI-ready" data and services along with (2) neurosymbolic AI methods to improve the quality of predictions and to generate plausible explanations. Attention is given to standards, platforms, and methods to wrangle knowledge into simple, but effective semantic and latent representations, and to make these available into standards-compliant and discoverable interfaces that can be used in model building, validation, and explanation. Our work, and those of others in the field, creates a baseline for building trustworthy and easy to deploy AI models in biomedicine.
Bio
Dr. Michel Dumontier is the Distinguished Professor of Data Science at Maastricht University, founder and executive director of the Institute of Data Science, and co-founder of the FAIR (Findable, Accessible, Interoperable and Reusable) data principles. His research explores socio-technological approaches for responsible discovery science, which includes collaborative multi-modal knowledge graphs, privacy-preserving distributed data mining, and AI methods for drug discovery and personalized medicine. His work is supported through the Dutch National Research Agenda, the Netherlands Organisation for Scientific Research, Horizon Europe, the European Open Science Cloud, the US National Institutes of Health, and a Marie-Curie Innovative Training Network. He is the editor-in-chief for the journal Data Science and is internationally recognized for his contributions in bioinformatics, biomedical informatics, and semantic technologies including ontologies and linked data.
This pdf is about the Schizophrenia.
For more details visit on YouTube; @SELF-EXPLANATORY;
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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.
Nutraceutical market, scope and growth: Herbal drug technologyLokesh Patil
As consumer awareness of health and wellness rises, the nutraceutical market—which includes goods like functional meals, drinks, and dietary supplements that provide health advantages beyond basic nutrition—is growing significantly. As healthcare expenses rise, the population ages, and people want natural and preventative health solutions more and more, this industry is increasing quickly. Further driving market expansion are product formulation innovations and the use of cutting-edge technology for customized nutrition. With its worldwide reach, the nutraceutical industry is expected to keep growing and provide significant chances for research and investment in a number of categories, including vitamins, minerals, probiotics, and herbal supplements.
Body fluids_tonicity_dehydration_hypovolemia_hypervolemia.pptx
Probing the fermi_bubbles_in_ultraviolet_absorption_spectroscopic_signature_of_the_milky_way
1. Draft version January 2, 2015
Preprint typeset using LATEX style emulateapj v. 08/13/06
PROBING THE FERMI BUBBLES IN ULTRAVIOLET ABSORPTION:
A SPECTROSCOPIC SIGNATURE OF THE MILKY WAY’S BICONICAL NUCLEAR OUTFLOW1
Andrew J. Fox2
, Rongmon Bordoloi2
, Blair D. Savage3
, Felix J. Lockman4
, Edward B. Jenkins5
, Bart P.
Wakker3
, Joss Bland-Hawthorn6
, Svea Hernandez2
, Tae-Sun Kim7
, Robert A. Benjamin8
, David V. Bowen5
, &
Jason Tumlinson2
2 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218
3 Department of Astronomy, University of Wisconsin–Madison, 475 North Charter St., Madison, WI 53706
4 National Radio Astronomy Observatory, P.O. Box 2, Rt. 28/92, Green Bank, WV 24944
5 Princeton University Observatory, Princeton, NJ 08544
6 Institute of Astronomy, School of Physics, University of Sydney, NSW 2006, Australia
7 Osservatorio Astronomico di Trieste, Via G.B. Tiepolo 11, 34143 Trieste, Italy
8 Department of Physics, University of Wisconsin–Whitewater, 800 W. Main St., Whitewater, WI 53190
Draft version January 2, 2015
ABSTRACT
Giant lobes of plasma extend ≈55◦
above and below the Galactic Center, glowing in emission from
gamma rays (the Fermi Bubbles) to microwaves (the WMAP haze) and polarized radio waves. We
use ultraviolet absorption-line spectra from the Hubble Space Telescope to constrain the velocity of
the outflowing gas within these regions, targeting the quasar PDS 456 (ℓ, b=10.4◦
, +11.2◦
). This
sightline passes through a clear biconical structure seen in hard X-ray and gamma-ray emission near
the base of the northern Fermi Bubble. We report two high-velocity metal absorption components, at
vLSR=−235 and +250 km s−1
, which cannot be explained by co-rotating gas in the Galactic disk or
halo. Their velocities are suggestive of an origin on the front and back side of an expanding biconical
outflow emanating from the Galactic Center. We develop simple kinematic biconical outflow models
that can explain the observed profiles with an outflow velocity of 900 km s−1
and a full opening
angle of ≈110◦
(matching the X-ray bicone). This indicates Galactic Center activity over the last
≈2.5–4.0Myr, in line with age estimates of the Fermi Bubbles. The observations illustrate the use of
UV spectroscopy to probe the properties of swept-up gas venting into the Fermi Bubbles.
Subject headings: Galaxy: center — Galaxy: halo — Galaxy: evolution — ISM: jets and outflows —
ISM: kinematics and dynamics
1. INTRODUCTION
The nuclei of star-forming galaxies are the powerhouses
where super-massive black holes collect interstellar gas
from their surroundings, funnel it onto accretion disks,
and heat it to extreme temperatures. The energy re-
leased from these environments and from supernovae and
stellar winds drives gas out of galaxies through large-
scale Galactic winds (see reviews by Heckman 2002;
Veilleux et al. 2005). Many outflows in nearby star-
forming galaxies are nuclear in origin and biconical in
shape, as in NGC 3079 (Cecil et al. 2001, 2002), M82
(Bland & Tully 1988; Shopbell & Bland-Hawthorn 1998;
Ohyama et al. 2002), and NGC 1482 (Veilleux & Rupke
2002).
Our vantage point inside the dusty rotating disk of the
Milky Way hampers our knowledge of any Galactic nu-
clear outflow. Lockman (1984) noted an absence of H I in
the inner Galaxy and suggested it had been cleared out
by a wind. The first clear detection of a biconical outflow
was made in mid-IR emission and (on larger scales) in
Electronic address: afox@stsci.edu
1 Based on observations taken under program 13448 of the
NASA/ESA Hubble Space Telescope, obtained at the Space Tele-
scope Science Institute, which is operated by the Association of
Universities for Research in Astronomy, Inc., under NASA con-
tract NAS 5-26555, and under program 14B-299 of the NRAO
Green Bank Telescope, which is a facility of the National Science
Foundation operated under cooperative agreement by Associated
Universities, Inc.
hard X-ray emission (Bland-Hawthorn & Cohen 2003). It
has since become clear that the Galactic Center (GC) lies
between two giant, energetic lobes associated with out-
flowing gas. These lobes extend ≈55◦
above and below
the GC (≈12 kpc) and show enhanced emission across the
electromagnetic spectrum, including: (1) γ-ray emission,
i.e. the Fermi Bubbles (FBs; Su et al. 2010; Dobler et al.
2010; Ackermann et al. 2014); (2) soft X-ray emission at
their base (0.3–1.0 keV; Snowden et al. 1997; Kataoka et
al. 2013); (3) K-band microwave emission (23–94 GHz),
known as the so-called WMAP haze (Finkbeiner et al.
2004; Dobler & Finkbeiner 2008); (4) polarized radio
emission at 2.3 GHz (synchrotron radiation; Carretti et
al. 2013). Near the base of the FBs, within 700 pc of the
GC, McClure-Griffiths et al. (2013, hereafter MG13) re-
cently discovered a population of ≈100 small H I clouds
whose kinematics are consistent with a biconical outflow
with a velocity of ≈200 km s−1
.
Clearly, a nuclear outflow is being driven out from the
GC. Yet only a handful of GC sightlines have published
UV spectroscopy that constrains the kinematics, ioniza-
tion state, and elemental abundances of the nuclear out-
flow, including two AGN directions (Keeney et al. 2006)
and several stellar directions (Bowen et al. 2008; Zech et
al. 2008; Wakker et al. 2012). However, none of these
UV studies have probed a full sightline through the front
and back sides of the FBs within 20◦
of the GC, where
the γ-ray emission, X-ray emission, and (presumably)
2. 2 Fox et al.
Fig. 1.— Collage of gamma-ray and X-ray emission showing the striking biconical nuclear structure intercepted by the PDS 456 sightline.
The yellow/orange map is an all-sky Fermi image of the residual gamma-ray intensity in the 3–10 GeV range, in Galactic coordinates
centered on the GC (Ackermann et al. 2014; c AAS. Reproduced with permission). The Fermi Bubbles are the twin lobes in dark
orange at the center of the figure. Superimposed in gray-scale is the ROSAT diffuse 1.5 keV emission map, based on Snowden et al. 1997,
Bland-Hawthorn & Cohen 2003, and Veilleux et al. 2005. The inset on the right shows a zoom-in on the X-ray data. Adapted from Figure
22, The Spectrum and Morphology of the Fermi Bubbles, M. Ackermann et al., ApJ, Volume 793, Issue 1, 2014, Page 64.
wind activity is strongest. The only such sightline with
published data is the optical spectrum of the blue su-
pergiant LS 4825 (ℓ, b=1.7◦
, –6.6◦
, d=21±5 kpc), which
shows complex multi-component Ca II and Na I profiles
spanning ≈300 km s−1
(Ryans et al. 1997).
We have initiated an observing program with the Hub-
ble Space Telescope (HST) to study the gas in the GC
region (defined here as 0◦
< l < 30◦
and 330◦
< l < 360◦
)
with UV spectroscopy (Program IDs 12936 and 13448).
The quasar PDS 456 (zem=0.184, ℓ, b=10.4◦
,+11.2◦
, also
known as IRAS 17254-1413) has the lowest latitude and
smallest impact parameter to the GC (ρ=2.3 kpc) of any
AGN in our sample. Furthermore, this sightline is the
only AGN direction in our sample that passes through the
biconical region of enhanced ROSAT 1.5 keV X-ray emis-
sion centered on the GC (Snowden et al. 1997), where
the γ-ray emission is also strong since the direction in-
tersects the base of the northern FB (Su et al. 2010).
The PDS 456 direction (see Figure 1) is therefore of high
interest for looking for UV outflow signatures. There are
no known 21 cm (neutral) high-velocity clouds (HVCs)
in this direction (e.g. Putman et al. 2012).
In this Letter we present new UV and radio spectra
of PDS 456 to explore the properties of gas entrained in
the Galactic nuclear outflow. In Section 2 we discuss
the observations and their reduction. In Section 3 we
present the UV absorption-line spectra and discuss the
identification of outflow components. Motivated by the
component structure observed in our spectra, we present
numerical kinematic models of a nuclear biconical out-
flow in Section 4. In Section 5 we present a discussion of
our results. A full discussion of other directions that pen-
etrate the northern and southern FBs will be presented
in an upcoming paper.
2. OBSERVATIONS AND DATA REDUCTION
2.1. COS Spectra
PDS 456 was observed on February 10 2014 with the
Cosmic Origins Spectrograph (COS; Green et al. 2012)
onboard HST for a total of five orbits. The observations
used the G130M/1291 and G160M/1600 grating/central
wavelength settings, all four FP-POS positions, and ex-
posure times of 4846 s for G130M and 8664 s for G160M.
Individual exposures were aligned in velocity space us-
ing the centroids of known low-ion interstellar absorption
lines, and then co-added following the same procedures
as described in Fox et al. (2014). The spectra have a
velocity resolution (FWHM) of ≈20 km s−1
, a signal-to-
noise ratio near the absorption lines of interest of ≈12–20
(per resolution element), an absolute velocity scale un-
certainty of ≈5 km s−1
, and cover the wavelength interval
1133–1778˚A, with small gaps between detector segments
at 1279–1288 and 1587–1598˚A. The spectra were normal-
ized around each absorption line using linear continua
and for display are rebinned by seven pixels (one reso-
lution element), though the Voigt-profile fits (described
below) were made on the unbinned data.
2.2. GBT Spectra
We obtained several deep H I 21 cm pointings of
the PDS 456 direction using the Green Bank Telescope
3. The Biconical Galactic Nuclear Outflow 3
(GBT) under NRAO program GBT/14B-299, with the
goal of detecting the HV components in emission. Multi-
ple scans of PDS 456 were taken on October 3 and Octo-
ber 4 2014 with the VEGAS spectrometer in frequency-
switching mode, for a total of 35 minutes of integra-
tion. The data were taken by frequency-switching ei-
ther 3.6 or 4.0 MHz, resulting in an unconfused veloc-
ity range of at least 760 km s−1
about zero velocity at
an intrinsic channel spacing of 0.151 km s−1
. The spec-
tra were Hanning smoothed, then calibrated and cor-
rected for stray radiation using the procedure described
by Boothroyd et al. (2011). One of the receiver’s two lin-
ear polarizations (PLNUM=1) gave consistently superior
instrumental baselines so only those data were used. A
fourth-order polynomial was removed from emission-free
portions of the final average. The resulting spectrum
has an rms brightness temperature noise of 17.5 mK in
a 0.30 km s−1
channel, giving a 1σ sensitivity to a line
40 km s−1
wide (chosen to be typical of Galactic HVCs)
of N(H I)=1.1×1017
cm−2
.
3. IDENTIFICATION OF OUTFLOW COMPONENTS
The COS spectra of PDS 456 show four absorption
components (see Figure 2), centered at vLSR=−235, −5,
+130, and +250 km s−1
. Absorption is seen in low-
ionization (C II, Si II, Al II), intermediate-ionization
(Si III), and high-ionization (C IV, Si IV, N V) species,
though the relative strength of absorption differs between
components. The −235, −5, and +130 km s−1
compo-
nents show absorption in the low, intermediate, and high
ions, whereas the +250 km s−1
component is seen in the
low- and intermediate ions only (no C IV, Si IV, or N V).
H I emission in the GBT spectrum is only seen in the
−5 km s−1
component; in the other three components no
H I detection is made down to a sensitive 3σ upper limit
N(H I)<3.3×1017
cm−2
. The ionic column densities in
the absorption components are given in Table 1. These
were determined by fitting Voigt profiles to the data with
the VPFIT software2
, using simultaneous fits to all avail-
able lines of a given ion.
Foreground gas in the rotating disk of the Galaxy pro-
duces absorption at a range of LSR velocities, and a sim-
ple model of Galactic rotation can be used to predict the
maximal allowed velocities for a given latitude and lon-
gitude (e.g. Savage & Massa 1987), assuming cylindrical
co-rotation. Absorption detected outside this velocity
interval can be attributed to inflow or outflow. Toward
PDS 456 the minimum and maximum LSR velocities are
≈0 km s−1
(at a distance of 0.0 kpc) and +174 km s−1
(at
8.8 kpc), respectively. Therefore:
(1) the strong −5 km s−1
component can be (either par-
tially or completely) explained by foreground gas in the
Galactic disk.
(2) the +130 km s−1
component corresponds to distances
of 7.1 and 9.9 kpc for co-rotation and so could also
be tracing Galactic material at z-distances of 1.4 and
1.9 kpc, respectively. However, for distant inner Galaxy
sightlines, the assumption of co-rotation breaks down at
|z|>1 kpc (Savage et al. 1990; Sembach et al. 1991), po-
tentially because the gas has been cleared out by a wind.
Thus the +130 km s−1
component might trace a nuclear
outflow, but we cannot conclusively determine its origin.
2 Available at http://www.ast.cam.ac.uk/∼rfc/vpfit.html
Fig. 2.— HST/COS and GBT spectra of the quasar PDS 456.
Normalized flux is plotted against LSR velocity for all UV metal
absorption lines that show high-velocity (HV) absorption (with
low ions in the left column and intermediate/high ions in the right
column). The GBT H I 21 cm emission spectrum is included in
the top-left panel. Absorption-line components are observed at
vLSR=−235, −5, +130, and +250 km s−1; only the −5 km s−1 com-
ponent is seen in 21 cm emission. Red lines indicate Voigt-profile
fits. The −5 km s−1 (unshaded) and +130 km s−1 (yellow) com-
ponents have velocities consistent with co-rotating foreground gas.
However, the −235 km s−1 (blue) and +250 km s−1 (orange) com-
ponents cannot be explained by co-rotation; instead, their veloci-
ties are suggestive of gas swept up by a biconical outflow. In this
scenario the near-side of the outflowing cone gives the −235 km s−1
component and the far-side gives the +250 km s−1 component.
(3) the −235 and +250 km s−1
components are at least
235 and 76 km s−1
away from co-rotation, respectively,
4. 4 Fox et al.
Fig. 3.— Numerical models of the Galactic biconical nuclear
outflow, which can explain the observed absorption-line kinematics.
The models have a constant outflow velocity of 900 km s−1 and a
full opening angle of 110◦ (tuned to match the X-ray bicone). We
investigate two sets of models: constant-velocity and momentum-
driven. Top: Top view of the momentum-driven outflow, looking
down on the Galactic plane. Each outflow particle is color-coded
by its LSR velocity. The near side of the outflow is blueshifted
and the far-side of the outflow is redshifted. Middle: Side view
of the momentum-driven outflow, showing the latitude where the
PDS 456 sightline intercepts the bicone. Bottom: Distribution of
LSR velocities of the outflow particles along the PDS 456 sightline
in 100 realizations of the models, for both the constant-velocity
(blue line) and momentum-driven (purple line) cases. The inset
panel shows the velocity profile of the two models. The centroids
of the observed components in the PDS 456 spectrum are shown
with vertical lines.
and are therefore of most interest for a nuclear outflow.
In the Galactic Standard of Rest (GSR), their velocities
are −190 and +295 km s−1
, assuming the rotation veloc-
ity at the solar circle is +254 km s−1
(Reid et al. 2009),
and where vGSR=vLSR+254 sin ℓ cos b. The velocities of
these two components are consistent with an origin on
the front (approaching) and back (receding) sides of a
biconical nuclear outflow emanating from the GC, a sce-
nario modeled in Section 4 and discussed in Section 5.
We note that the observed low-velocity high-ion ab-
sorption (C IV, Si IV, and N V) is strong compared to
other (non-GC) Galactic halo sight lines (Savage et al.
2001; Wakker et al. 2012). In particular, C IV shows
a ≈0.5 dex excess in low-velocity column density, which
may be another sign of GC activity.
4. BICONICAL OUTFLOW NUMERICAL MODELS
We develop simple numerical models to explore the
kinematic predictions of a biconical nuclear outflow. The
models are based on the Mg II outflow models of Bordoloi
et al. (2014). We assume the outflow is an non-rotating
expanding bicone centered on the GC with a constant
mass flux. A population of 107
test particles is inserted
at the base of the outflow, with a uniform filling factor.
The three principal free parameters in the models are
the initial outflow velocity vout, the full opening angle α
of the bicone, and the velocity profile. We take α=110◦
based on the bicone seen in the ROSAT 1.5 keV image
(Figure 1) and investigate the value of vout needed to
explain the −235 and +250 km s−1
components. We ex-
plore two cases for the velocity profile: constant-velocity
(the simplest case), and momentum-driven, where the
outflow climbs ballistically out of the Galactic potential
after being given an initial impulse (e.g. by ram pressure
from a hot wind). In the latter case we use the for-
malism of Murray et al. (2005) and Dijkstra & Kramer
(2012) to express the velocity as a function of radius
from the GC. We assume the outflow reaches a radial
distance of at least 4 kpc, distant enough to ensure the
PDS 456 sightline fully intercepts the bicone (see Figure
3, middle panel). The models are initially computed in
the GSR reference frame, but are transformed into the
LSR frame for comparison with the data. For both the
constant-velocity and momentum-driven cases, 100 re-
alizations of the models are created, and for each one a
line-of-sight with the PDS 456 coordinates was generated
and the kinematic structure measured. The models do
not account for the physical or kinematic properties of
the external gaseous medium that confines the flow.
The models are shown in Figure 3. We find vout
900 km s−1
; lower velocities do not account for the
−235 km s−1
component. Figures 3a (top view) and 3b
(side view) show the velocity structure of the outflow as
observed from vantage points outside the Galaxy. These
plots illustrate the correspondence between LSR velocity
and distance along the line-of-sight. The velocity fields
are asymmetric with respect to the vertical because of
the transformation from the GSR to LSR frame, i.e. be-
cause we are observing the outflow from a co-rotating
frame at a fixed distance. Figure 3c shows the distri-
bution of outflow velocities projected onto the PDS 456
line-of-sight drawn from 100 realizations of each of the
two models. Discrete kinematic structure is seen in any
single realization of the model (not shown in figure), but
the component velocities differ substantially between any
two model runs, so we show the distribution to indicate
the range of velocities predicted.
There are several points to note from the model veloc-
ity distributions. First, the distributions are fairly flat
for both constant-velocity and momentum-driven winds,
which reflects our choice of model in which gas exists with
uniform filling factor within the outflow, not just at the
edges. The prediction of outflowing gas with LSR veloci-
ties near 0 km s−1
could explain the 0.5 dex excess in low-
5. The Biconical Galactic Nuclear Outflow 5
velocity high-ion absorption seen toward PDS 456. Sec-
ond, the distributions are asymmetric around zero, rang-
ing from ≈–250 km s−1
(this velocity is a consequence of
the requirement that we explain the −235 km s−1
compo-
nent toward PDS 456) to ≈+550 km s−1
for the constant-
velocity wind, and ≈+300km s−1
for the momentum-
driven wind. This asymmetry is a projection effect aris-
ing because of the finite distance between the Sun and
the GC (the near-field effect). Third, the momentum-
driven wind model is more successful in reproducing the
range of velocity components seen toward PDS 456 than
the constant-velocity wind model, since the latter pre-
dicts gas in the range ≈300–600km s−1
, which is not ob-
served. Models in which gas flows out preferentially along
the edges of the cone are also consistent with the data,
but are outside the scope of this Letter. In summary, the
simple momentum-driven biconical wind model is able to
reproduce the velocities of the HV components toward
PDS 456.
5. DISCUSSION
The HST/COS spectrum of PDS 456, a QSO lying
only 15.2◦
from the GC in a direction of enhanced
X-ray and γ-ray emission intercepting the base of the
northern FB, shows UV metal-absorption-line compo-
nents at vLSR=−235 and +250 km s−1
(corresponding
to vGSR=–190 and +295 km s−1
), velocities which can-
not be explained by gas in the low halo of the inner
Galaxy co-rotating with the disk. A further compo-
nent at +130 km s−1
is also difficult to explain via co-
rotation. None of the components shows 21 cm emis-
sion in our GBT spectrum down to sensitive levels of
N(H I)<3.3×1017
cm−2
(3σ), which indicates the hydro-
gen is mostly ionized. The kinematics of these compo-
nents can be explained in a scenario where cool swept-up
gas is entrained on the near- (blueshifted) and far- (red-
shifted) side of a biconical outflow from the GC.
There are several arguments supporting the biconical
outflow explanation: (1) the ROSAT X-ray imaging and
Fermi γ-ray imaging both clearly indicate the presence
of a biconical structure centered on the GC and inter-
sected by the PDS 456 sightline; (2) simple kinematic
models of a biconical outflow (Section 4) naturally repro-
duce the presence of both negative- and positive-velocity
gas components; (3) such models also explain the excess
low-velocity high-ion absorption; (4) the MG13 results
demonstrate a population of H I clumps existing closer to
the GC with kinematics consistent with a biconical out-
flow; (5) although we cannot rule out the possibility that
individual HV absorbers arise in unrelated foreground or
background HVCs, which have a sky covering fraction in
UV metal lines of ≈68–80% (Collins et al. 2009; Shull et
al. 2009; Lehner et al. 2012), a chance alignment of two
unrelated HVCs at close-to-symmetric velocities of −235
and +250 km s−1
would be needed to emulate the pro-
files of a biconical outflow; (6) given the low latitude of
the PDS 456 sightline (b=+11.2◦
), explaining the −235
and +250 km s−1
components as being regular (non-GC)
HVCs would require unusually large ( 1000 km s−1
) ver-
tical inflow or outflow velocities, because of the projec-
tion factor sin b. This makes it highly unlikely that the
PDS 456 HV components are due to regular HVCs or
to tidally-stripped material like the Magellanic Stream,
which have much lower vertical flow velocities (∼100–
200 km s−1
).
In the biconical outflow interpretation, the hot wind
phase is feeding the FBs with new plasma (e.g. Crocker
2012), whereas the cool low-ion gas represents swept-up
material entrained in the outflow. We stress that our
HST/COS observations do not directly probe the hot
phase, but instead probe cool (T ∼104
K) entrained gas
via the low ions and transition-temperature (T ∼105
K)
gas via the high ions, which may trace the boundaries
between the cool gas and the hot wind. The cool out-
flowing gas has already been detected, albeit closer to
the GC with a much lower wind velocity, via the MG13
population of H I clouds. Despite the disruptive instabil-
ities that can destroy cold filaments and clouds on short
timescales, simulations show that such structures can
survive in the hot wind fluid if stabilized by magnetic
fields or other mechanisms (Cooper et al. 2008; McCourt
et al. 2014).
Our models find the outflow velocity is 900 km s−1
;
such a flow must be ≈2.5–4.0Myr old to reach 2.3 kpc,
the impact parameter of the PDS 456 sightline. This
wind age is consistent with the timescale of energy injec-
tion that created the FBs, whether via AGN jets (Guo &
Mathews 2012; Yang et al. 2012), feedback from nuclear
star formation (Crocker & Aharonian 2011; Carretti et
al. 2013; Lacki 2014), accretion flows onto Sgr A∗
(Cheng
et al. 2011; Mou et al. 2014), or a spherical outflow from
Sgr A∗
(Zubovas et al. 2011). It is also compatible with
the observed Hα emission from the Magellanic Stream,
which is consistent with an origin following a Seyfert flare
at the GC 1–3 Myr ago (Bland-Hawthorn et al. 2013).
In our upcoming work, we will analyze the UV spec-
tra of other GC targets, including foreground stars at
a range of distance and background AGN at a range of
latitude, both inside and outside the FBs. A large sam-
ple of sightlines is needed to fully characterize the extent
and nature of the Galactic nuclear outflow.
Acknowledgments. Support for program 13448 was
provided by NASA through grants from the Space Tele-
scope Science Institute, which is operated by the Asso-
ciation of Universities for Research in Astronomy, Inc.,
under NASA contract NAS 5-26555. The National Radio
Astronomy Observatory is a facility of the National Sci-
ence Foundation operated under cooperative agreement
by Associated Universities, Inc. We thank Gerald Cecil
for assistance with Figure 1 and the referee for an insight-
ful report. We thank Anne Franckowiak and the Fermi-
LAT collaboration for permission to reproduce their all-
sky residual intensity map. JBH is funded by an ARC
Laureate Fellowship. TSK acknowledges support from a
European Research Council Starting Grant in cosmology
and the IGM under Grant Agreement (GA) 257670.
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TABLE 1
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