The ALMA observations of NGC 1433 reveal a nuclear gaseous spiral structure within the central kpc. This spiral winds up into a pseudo-ring at ~200 pc from the center. Near the nucleus, there is intense high-velocity CO emission up to 200 km/s that is interpreted as an outflow, involving 3.6 million solar masses of molecular gas and a flow rate of ~7 solar masses per year. The outflow could be driven by both the central star formation and AGN through its radio jets. Continuum emission at 0.87 mm is detected only at the very center and likely comes from thermal dust emission from the molecular torus expected in this Seyfert 2 galaxy.
T he effect_of_orbital_configuration)_on_the_possible_climates_and_habitabili...Sérgio Sacani
As lower-mass stars often host multiple rocky planets, gravitational interactions among planets can have significant
effects on climate and habitability over long timescales. Here we explore a specific case, Kepler-62f (Borucki et al.,
2013), a potentially habitable planet in a five-planet system with a K2V host star. N-body integrations reveal the
stable range of initial eccentricities for Kepler-62f is 0.00 £ e £ 0.32, absent the effect of additional, undetected
planets. We simulate the tidal evolution of Kepler-62f in this range and find that, for certain assumptions, the planet
can be locked in a synchronous rotation state. Simulations using the 3-D Laboratoire de Me´te´orologie Dynamique
(LMD) Generic global climate model (GCM) indicate that the surface habitability of this planet is sensitive to
orbital configuration.With 3 bar of CO2 in its atmosphere, we find that Kepler-62f would only be warm enough for
surface liquid water at the upper limit of this eccentricity range, providing it has a high planetary obliquity
(between 60 and 90). A climate similar to that of modern-day Earth is possible for the entire range of stable
eccentricities if atmospheric CO2 is increased to 5 bar levels. In a low-CO2 case (Earth-like levels), simulations
with version 4 of the Community Climate System Model (CCSM4) GCM and LMD Generic GCM indicate that
increases in planetary obliquity and orbital eccentricity coupled with an orbital configuration that places the
summer solstice at or near pericenter permit regions of the planet with above-freezing surface temperatures. This
may melt ice sheets formed during colder seasons. If Kepler-62f is synchronously rotating and has an ocean, CO2
levels above 3 bar would be required to distribute enough heat to the nightside of the planet to avoid atmospheric
freeze-out and permit a large enough region of open water at the planet’s substellar point to remain stable. Overall,
we find multiple plausible combinations of orbital and atmospheric properties that permit surface liquid water on
Kepler-62f. Key Words: Extrasolar planets—Habitability—Planetary environments. Astrobiology 16, xxx–xxx.
The canarias einstein_ring_a_newly_discovered_optical_einstein_ringSérgio Sacani
We report the discovery of an optical Einstein Ring in the Sculptor constellation,
IAC J010127-334319, in the vicinity of the Sculptor Dwarf Spheroidal Galaxy. It is
an almost complete ring ( 300◦) with a diameter of 4.5 arcsec. The discovery was
made serendipitously from inspecting Dark Energy Camera (DECam) archive imaging
data. Confirmation of the object nature has been obtained by deriving spectroscopic
redshifts for both components, lens and source, from observations at the 10.4 m Gran
Telescopio CANARIAS (GTC) with the spectrograph OSIRIS. The lens, a massive
early-type galaxy, has a redshift of z = 0.581 while the source is a starburst galaxy
with redshift of z = 1.165. The total enclosed mass that produces the lensing effect
has been estimated to be Mtot = (1.86 ± 0.23) · 1012M⊙.
The importance of comets for the origin of life on Earth has been advocated for many decades. Amino acids are
key ingredients in chemistry, leading to life as we know it. Many primitive meteorites contain amino acids, and it
is generally believed that these are formed by aqueous alterations. In the collector aerogel and foil samples of the
Stardust mission after the flyby at comet Wild 2, the simplest form of amino acids, glycine, has been found
together with precursor molecules methylamine and ethylamine. Because of contamination issues of the samples,
a cometary origin was deduced from the 13C isotopic signature. We report the presence of volatile glycine
accompanied by methylamine and ethylamine in the coma of 67P/Churyumov-Gerasimenko measured by
the ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) mass spectrometer, confirming the
Stardust results. Together with the detection of phosphorus and a multitude of organic molecules, this result
demonstrates that comets could have played a crucial role in the emergence of life on Earth.
First identification of_direct_collapse_black_holes_candidates_in_the_early_u...Sérgio Sacani
The first black hole seeds, formed when the Universe was younger than ⇠ 500Myr, are recognized
to play an important role for the growth of early (z ⇠ 7) super-massive black holes.
While progresses have been made in understanding their formation and growth, their observational
signatures remain largely unexplored. As a result, no detection of such sources has been
confirmed so far. Supported by numerical simulations, we present a novel photometric method
to identify black hole seed candidates in deep multi-wavelength surveys.We predict that these
highly-obscured sources are characterized by a steep spectrum in the infrared (1.6−4.5μm),
i.e. by very red colors. The method selects the only 2 objects with a robust X-ray detection
found in the CANDELS/GOODS-S survey with a photometric redshift z & 6. Fitting their
infrared spectra only with a stellar component would require unrealistic star formation rates
(& 2000M# yr−1). To date, the selected objects represent the most promising black hole seed
candidates, possibly formed via the direct collapse black hole scenario, with predicted mass
> 105M#. While this result is based on the best photometric observations of high-z sources
available to date, additional progress is expected from spectroscopic and deeper X-ray data.
Upcoming observatories, like the JWST, will greatly expand the scope of this work.
Storm in teacup_a_radio_quiet_quasar_with_radio_emitting_bubblesSérgio Sacani
Artigo descreve descoberta feita com o VLA de uma tempestade nas ondas de rádio em uma galáxia até então calma, o que traz conclusões sobre a evolução das galáxias.
A 2 4_determination_of_the_local_value_of_the_hubble_constantSérgio Sacani
We use the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST) to
reduce the uncertainty in the local value of the Hubble constant from 3.3% to 2.4%.
The bulk of this improvement comes from new, near-infrared observations of Cepheid
variables in 11 host galaxies of recent type Ia supernovae (SNe Ia), more than doubling
the sample of reliable SNe Ia having a Cepheid-calibrated distance to a total of 19; these
in turn leverage the magnitude-redshift relation based on 300 SNe Ia at z <0.15. All
19 hosts as well as the megamaser system NGC4258 have been observed with WFC3
in the optical and near-infrared, thus nullifying cross-instrument zeropoint errors in the
relative distance estimates from Cepheids. Other noteworthy improvements include a
33% reduction in the systematic uncertainty in the maser distance to NGC4258, a larger
sample of Cepheids in the Large Magellanic Cloud (LMC), a more robust distance to
the LMC based on late-type detached eclipsing binaries (DEBs), HST observations of
Cepheids in M31, and new HST-based trigonometric parallaxes for Milky Way (MW)
Cepheids.
Exocometary gas in_th_hd_181327_debris_ringSérgio Sacani
An increasing number of observations have shown that gaseous debris discs are not an
exception. However, until now we only knew of cases around A stars. Here we present the first
detection of 12CO (2-1) disc emission around an F star, HD 181327, obtained with ALMA
observations at 1.3 mm. The continuum and CO emission are resolved into an axisymmetric
disc with ring-like morphology. Using a Markov chain Monte Carlo method coupled with
radiative transfer calculations we study the dust and CO mass distribution. We find the dust is
distributed in a ring with a radius of 86:0 0:4 AU and a radial width of 23:2 1:0 AU. At
this frequency the ring radius is smaller than in the optical, revealing grain size segregation
expected due to radiation pressure. We also report on the detection of low level continuum
emission beyond the main ring out to 200 AU. We model the CO emission in the non-LTE
regime and we find that the CO is co-located with the dust, with a total CO gas mass ranging
between 1:2 10 6 M and 2:9 10 6 M, depending on the gas kinetic temperature and
collisional partners densities. The CO densities and location suggest a secondary origin, i.e.
released from icy planetesimals in the ring. We derive a CO cometary composition that is
consistent with Solar system comets. Due to the low gas densities it is unlikely that the gas is
shaping the dust distribution.
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.
Supermassive black holes in galaxy centres can grow by the accretion
of gas, liberating enormous amounts of energy that might
regulate star formation on galaxy-wide scales1–3
. The nature of
gaseous fuel reservoirs that power black hole growth is nevertheless
largely unconstrained by observations, and is instead routinely
simplified as a smooth, spherical inflow of very hot gas
in accordance with the Bondi solution4
. Recent theory5–7 and
simulations8–10 instead predict that accretion can be dominated by
a stochastic, clumpy distribution of very cold molecular clouds,
though unambiguous observational support for this prediction remains
elusive. Here we show observational evidence for a cold,
clumpy accretion flow toward a supermassive black hole fuel reservoir
in the nucleus of the Abell 2597 Brightest Cluster Galaxy
(BCG), a nearby (z = 0.0821) giant elliptical galaxy surrounded
by a dense halo of hot plasma11–13. Under the right conditions,
thermal instabilities can precipitate from this hot gas, producing a
rain of cold clouds that fall toward the galaxy’s centre14, sustaining
star formation amid a kiloparsec-scale molecular nebula that inhabits
its core15. New interferometric sub-millimetre observations
show that these cold clouds also fuel black hole accretion, revealing
“shadows” cast by molecular clouds as they move inward at ∼ 300
km s−1
toward the active supermassive black hole in the galaxy
centre, which serves as a bright backlight. Corroborating evidence
from prior observations16 of warmer atomic gas at extremely high
spatial resolution17, along with simple arguments based on geometry
and probability, indicates that these clouds are within the innermost
hundred parsecs of the black hole, and falling closer toward
it
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)
Evidence for the_thermal_sunyaev-zeldovich_effect_associated_with_quasar_feed...Sérgio Sacani
Using a radio-quiet subsample of the Sloan Digital Sky Survey spectroscopic quasar
catalogue, spanning redshifts 0.5–3.5, we derive the mean millimetre and far-infrared
quasar spectral energy distributions (SEDs) via a stacking analysis of Atacama Cosmology
Telescope and Herschel-Spectral and Photometric Imaging REceiver data. We
constrain the form of the far-infrared emission and find 3σ–4σ evidence for the thermal
Sunyaev-Zel’dovich (SZ) effect, characteristic of a hot ionized gas component with
thermal energy (6.2 ± 1.7) × 1060 erg. This amount of thermal energy is greater than
expected assuming only hot gas in virial equilibrium with the dark matter haloes of
(1 − 5) × 1012h
−1M that these systems are expected to occupy, though the highest
quasar mass estimates found in the literature could explain a large fraction of this
energy. Our measurements are consistent with quasars depositing up to (14.5±3.3) τ
−1
8
per cent of their radiative energy into their circumgalactic environment if their typical
period of quasar activity is τ8 × 108 yr. For high quasar host masses, ∼ 1013h
−1M,
this percentage will be reduced. Furthermore, the uncertainty on this percentage is
only statistical and additional systematic uncertainties enter at the 40 per cent level.
The SEDs are dust dominated in all bands and we consider various models for dust
emission. While sufficiently complex dust models can obviate the SZ effect, the SZ
interpretation remains favoured at the 3σ–4σ level for most models.
SPECTROSCOPIC CONFIRMATION OF THE EXISTENCE OF LARGE, DIFFUSE GALAXIES IN THE...Sérgio Sacani
We recently identified a population of low surface brightness objects in the field of the z = 0.023 Coma cluster,
using the Dragonfly Telephoto Array. Here we present Keck spectroscopy of one of the largest of these “ultradiffuse
galaxies” (UDGs), confirming that it is a member of the cluster. The galaxy has prominent absorption
features, including the Ca II H+K lines and the G-band, and no detected emission lines. Its radial velocity of
cz=6280±120 km s−1 is within the 1σ velocity dispersion of the Coma cluster. The galaxy has an effective
radius of 4.3 ± 0.3 kpc and a Sérsic index of 0.89 ± 0.06, as measured from Keck imaging. We find no indications
of tidal tails or other distortions, at least out to a radius of ∼2re. We show that UDGs are located in a previously
sparsely populated region of the size—magnitude plane of quiescent stellar systems, as they are ∼6 mag fainter
than normal early-type galaxies of the same size. It appears that the luminosity distribution of large quiescent
galaxies is not continuous, although this could largely be due to selection effects. Dynamical measurements are
needed to determine whether the dark matter halos of UDGs are similar to those of galaxies with the same
luminosity or to those of galaxies with the same size.
The most luminous_galaxies_discovered_by_wiseSérgio Sacani
Artigo descreve estudo feito por astrônomos e com a ajuda da sonda WISE da NASA para identificar as galáxias do tipo ELIRGs, entre elas a mais luminosa galáxia do universo, com um buraco negro gigantesco em seu interior e localizada a cerca de 12.8 bilhões de anos de distância da Terra.
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.
T he effect_of_orbital_configuration)_on_the_possible_climates_and_habitabili...Sérgio Sacani
As lower-mass stars often host multiple rocky planets, gravitational interactions among planets can have significant
effects on climate and habitability over long timescales. Here we explore a specific case, Kepler-62f (Borucki et al.,
2013), a potentially habitable planet in a five-planet system with a K2V host star. N-body integrations reveal the
stable range of initial eccentricities for Kepler-62f is 0.00 £ e £ 0.32, absent the effect of additional, undetected
planets. We simulate the tidal evolution of Kepler-62f in this range and find that, for certain assumptions, the planet
can be locked in a synchronous rotation state. Simulations using the 3-D Laboratoire de Me´te´orologie Dynamique
(LMD) Generic global climate model (GCM) indicate that the surface habitability of this planet is sensitive to
orbital configuration.With 3 bar of CO2 in its atmosphere, we find that Kepler-62f would only be warm enough for
surface liquid water at the upper limit of this eccentricity range, providing it has a high planetary obliquity
(between 60 and 90). A climate similar to that of modern-day Earth is possible for the entire range of stable
eccentricities if atmospheric CO2 is increased to 5 bar levels. In a low-CO2 case (Earth-like levels), simulations
with version 4 of the Community Climate System Model (CCSM4) GCM and LMD Generic GCM indicate that
increases in planetary obliquity and orbital eccentricity coupled with an orbital configuration that places the
summer solstice at or near pericenter permit regions of the planet with above-freezing surface temperatures. This
may melt ice sheets formed during colder seasons. If Kepler-62f is synchronously rotating and has an ocean, CO2
levels above 3 bar would be required to distribute enough heat to the nightside of the planet to avoid atmospheric
freeze-out and permit a large enough region of open water at the planet’s substellar point to remain stable. Overall,
we find multiple plausible combinations of orbital and atmospheric properties that permit surface liquid water on
Kepler-62f. Key Words: Extrasolar planets—Habitability—Planetary environments. Astrobiology 16, xxx–xxx.
The canarias einstein_ring_a_newly_discovered_optical_einstein_ringSérgio Sacani
We report the discovery of an optical Einstein Ring in the Sculptor constellation,
IAC J010127-334319, in the vicinity of the Sculptor Dwarf Spheroidal Galaxy. It is
an almost complete ring ( 300◦) with a diameter of 4.5 arcsec. The discovery was
made serendipitously from inspecting Dark Energy Camera (DECam) archive imaging
data. Confirmation of the object nature has been obtained by deriving spectroscopic
redshifts for both components, lens and source, from observations at the 10.4 m Gran
Telescopio CANARIAS (GTC) with the spectrograph OSIRIS. The lens, a massive
early-type galaxy, has a redshift of z = 0.581 while the source is a starburst galaxy
with redshift of z = 1.165. The total enclosed mass that produces the lensing effect
has been estimated to be Mtot = (1.86 ± 0.23) · 1012M⊙.
The importance of comets for the origin of life on Earth has been advocated for many decades. Amino acids are
key ingredients in chemistry, leading to life as we know it. Many primitive meteorites contain amino acids, and it
is generally believed that these are formed by aqueous alterations. In the collector aerogel and foil samples of the
Stardust mission after the flyby at comet Wild 2, the simplest form of amino acids, glycine, has been found
together with precursor molecules methylamine and ethylamine. Because of contamination issues of the samples,
a cometary origin was deduced from the 13C isotopic signature. We report the presence of volatile glycine
accompanied by methylamine and ethylamine in the coma of 67P/Churyumov-Gerasimenko measured by
the ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) mass spectrometer, confirming the
Stardust results. Together with the detection of phosphorus and a multitude of organic molecules, this result
demonstrates that comets could have played a crucial role in the emergence of life on Earth.
First identification of_direct_collapse_black_holes_candidates_in_the_early_u...Sérgio Sacani
The first black hole seeds, formed when the Universe was younger than ⇠ 500Myr, are recognized
to play an important role for the growth of early (z ⇠ 7) super-massive black holes.
While progresses have been made in understanding their formation and growth, their observational
signatures remain largely unexplored. As a result, no detection of such sources has been
confirmed so far. Supported by numerical simulations, we present a novel photometric method
to identify black hole seed candidates in deep multi-wavelength surveys.We predict that these
highly-obscured sources are characterized by a steep spectrum in the infrared (1.6−4.5μm),
i.e. by very red colors. The method selects the only 2 objects with a robust X-ray detection
found in the CANDELS/GOODS-S survey with a photometric redshift z & 6. Fitting their
infrared spectra only with a stellar component would require unrealistic star formation rates
(& 2000M# yr−1). To date, the selected objects represent the most promising black hole seed
candidates, possibly formed via the direct collapse black hole scenario, with predicted mass
> 105M#. While this result is based on the best photometric observations of high-z sources
available to date, additional progress is expected from spectroscopic and deeper X-ray data.
Upcoming observatories, like the JWST, will greatly expand the scope of this work.
Storm in teacup_a_radio_quiet_quasar_with_radio_emitting_bubblesSérgio Sacani
Artigo descreve descoberta feita com o VLA de uma tempestade nas ondas de rádio em uma galáxia até então calma, o que traz conclusões sobre a evolução das galáxias.
A 2 4_determination_of_the_local_value_of_the_hubble_constantSérgio Sacani
We use the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST) to
reduce the uncertainty in the local value of the Hubble constant from 3.3% to 2.4%.
The bulk of this improvement comes from new, near-infrared observations of Cepheid
variables in 11 host galaxies of recent type Ia supernovae (SNe Ia), more than doubling
the sample of reliable SNe Ia having a Cepheid-calibrated distance to a total of 19; these
in turn leverage the magnitude-redshift relation based on 300 SNe Ia at z <0.15. All
19 hosts as well as the megamaser system NGC4258 have been observed with WFC3
in the optical and near-infrared, thus nullifying cross-instrument zeropoint errors in the
relative distance estimates from Cepheids. Other noteworthy improvements include a
33% reduction in the systematic uncertainty in the maser distance to NGC4258, a larger
sample of Cepheids in the Large Magellanic Cloud (LMC), a more robust distance to
the LMC based on late-type detached eclipsing binaries (DEBs), HST observations of
Cepheids in M31, and new HST-based trigonometric parallaxes for Milky Way (MW)
Cepheids.
Exocometary gas in_th_hd_181327_debris_ringSérgio Sacani
An increasing number of observations have shown that gaseous debris discs are not an
exception. However, until now we only knew of cases around A stars. Here we present the first
detection of 12CO (2-1) disc emission around an F star, HD 181327, obtained with ALMA
observations at 1.3 mm. The continuum and CO emission are resolved into an axisymmetric
disc with ring-like morphology. Using a Markov chain Monte Carlo method coupled with
radiative transfer calculations we study the dust and CO mass distribution. We find the dust is
distributed in a ring with a radius of 86:0 0:4 AU and a radial width of 23:2 1:0 AU. At
this frequency the ring radius is smaller than in the optical, revealing grain size segregation
expected due to radiation pressure. We also report on the detection of low level continuum
emission beyond the main ring out to 200 AU. We model the CO emission in the non-LTE
regime and we find that the CO is co-located with the dust, with a total CO gas mass ranging
between 1:2 10 6 M and 2:9 10 6 M, depending on the gas kinetic temperature and
collisional partners densities. The CO densities and location suggest a secondary origin, i.e.
released from icy planetesimals in the ring. We derive a CO cometary composition that is
consistent with Solar system comets. Due to the low gas densities it is unlikely that the gas is
shaping the dust distribution.
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.
Supermassive black holes in galaxy centres can grow by the accretion
of gas, liberating enormous amounts of energy that might
regulate star formation on galaxy-wide scales1–3
. The nature of
gaseous fuel reservoirs that power black hole growth is nevertheless
largely unconstrained by observations, and is instead routinely
simplified as a smooth, spherical inflow of very hot gas
in accordance with the Bondi solution4
. Recent theory5–7 and
simulations8–10 instead predict that accretion can be dominated by
a stochastic, clumpy distribution of very cold molecular clouds,
though unambiguous observational support for this prediction remains
elusive. Here we show observational evidence for a cold,
clumpy accretion flow toward a supermassive black hole fuel reservoir
in the nucleus of the Abell 2597 Brightest Cluster Galaxy
(BCG), a nearby (z = 0.0821) giant elliptical galaxy surrounded
by a dense halo of hot plasma11–13. Under the right conditions,
thermal instabilities can precipitate from this hot gas, producing a
rain of cold clouds that fall toward the galaxy’s centre14, sustaining
star formation amid a kiloparsec-scale molecular nebula that inhabits
its core15. New interferometric sub-millimetre observations
show that these cold clouds also fuel black hole accretion, revealing
“shadows” cast by molecular clouds as they move inward at ∼ 300
km s−1
toward the active supermassive black hole in the galaxy
centre, which serves as a bright backlight. Corroborating evidence
from prior observations16 of warmer atomic gas at extremely high
spatial resolution17, along with simple arguments based on geometry
and probability, indicates that these clouds are within the innermost
hundred parsecs of the black hole, and falling closer toward
it
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)
Evidence for the_thermal_sunyaev-zeldovich_effect_associated_with_quasar_feed...Sérgio Sacani
Using a radio-quiet subsample of the Sloan Digital Sky Survey spectroscopic quasar
catalogue, spanning redshifts 0.5–3.5, we derive the mean millimetre and far-infrared
quasar spectral energy distributions (SEDs) via a stacking analysis of Atacama Cosmology
Telescope and Herschel-Spectral and Photometric Imaging REceiver data. We
constrain the form of the far-infrared emission and find 3σ–4σ evidence for the thermal
Sunyaev-Zel’dovich (SZ) effect, characteristic of a hot ionized gas component with
thermal energy (6.2 ± 1.7) × 1060 erg. This amount of thermal energy is greater than
expected assuming only hot gas in virial equilibrium with the dark matter haloes of
(1 − 5) × 1012h
−1M that these systems are expected to occupy, though the highest
quasar mass estimates found in the literature could explain a large fraction of this
energy. Our measurements are consistent with quasars depositing up to (14.5±3.3) τ
−1
8
per cent of their radiative energy into their circumgalactic environment if their typical
period of quasar activity is τ8 × 108 yr. For high quasar host masses, ∼ 1013h
−1M,
this percentage will be reduced. Furthermore, the uncertainty on this percentage is
only statistical and additional systematic uncertainties enter at the 40 per cent level.
The SEDs are dust dominated in all bands and we consider various models for dust
emission. While sufficiently complex dust models can obviate the SZ effect, the SZ
interpretation remains favoured at the 3σ–4σ level for most models.
SPECTROSCOPIC CONFIRMATION OF THE EXISTENCE OF LARGE, DIFFUSE GALAXIES IN THE...Sérgio Sacani
We recently identified a population of low surface brightness objects in the field of the z = 0.023 Coma cluster,
using the Dragonfly Telephoto Array. Here we present Keck spectroscopy of one of the largest of these “ultradiffuse
galaxies” (UDGs), confirming that it is a member of the cluster. The galaxy has prominent absorption
features, including the Ca II H+K lines and the G-band, and no detected emission lines. Its radial velocity of
cz=6280±120 km s−1 is within the 1σ velocity dispersion of the Coma cluster. The galaxy has an effective
radius of 4.3 ± 0.3 kpc and a Sérsic index of 0.89 ± 0.06, as measured from Keck imaging. We find no indications
of tidal tails or other distortions, at least out to a radius of ∼2re. We show that UDGs are located in a previously
sparsely populated region of the size—magnitude plane of quiescent stellar systems, as they are ∼6 mag fainter
than normal early-type galaxies of the same size. It appears that the luminosity distribution of large quiescent
galaxies is not continuous, although this could largely be due to selection effects. Dynamical measurements are
needed to determine whether the dark matter halos of UDGs are similar to those of galaxies with the same
luminosity or to those of galaxies with the same size.
The most luminous_galaxies_discovered_by_wiseSérgio Sacani
Artigo descreve estudo feito por astrônomos e com a ajuda da sonda WISE da NASA para identificar as galáxias do tipo ELIRGs, entre elas a mais luminosa galáxia do universo, com um buraco negro gigantesco em seu interior e localizada a cerca de 12.8 bilhões de anos de distância da Terra.
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.
The xmm newton-view_of_the_central_degrees_of_the_milk_waySérgio Sacani
Novas imagens do Observatório de Raios-X XMM-Newton da ESA revelaram alguns dos processos mais intensos que acontecem no coração da nossa Via Láctea.
As fontes brilhantes e pontuais que se destacam por toda imagem indicam os sistemas estelares binários onde uma das estrelas atingiu o final de sua vida, desenvolvendo para um objeto compacto e denso – uma estrela de nêutrons ou um buraco negro.
A região central da Via Láctea também contém jovens estrelas e aglomerados estelares e algumas dessas fontes são visíveis como pontos brancos e vermelhos brilhando na imagem, que se espalha por 1000 anos-luz.
A maior parte da ação ocorre no centro, onde nuvens difusas de gás estão sendo cavadas por ventos poderosos soprados por estrelas jovens, bem como por supernovas.
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.
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.
Large scale mass_distribution_in_the_illustris_simulationSérgio Sacani
Observations at low redshifts thus far fail to account for all of the baryons expected in the
Universe according to cosmological constraints. A large fraction of the baryons presumably
resides in a thin and warm–hot medium between the galaxies, where they are difficult to observe
due to their low densities and high temperatures. Cosmological simulations of structure
formation can be used to verify this picture and provide quantitative predictions for the distribution
of mass in different large-scale structure components. Here we study the distribution
of baryons and dark matter at different epochs using data from the Illustris simulation. We
identify regions of different dark matter density with the primary constituents of large-scale
structure, allowing us to measure mass and volume of haloes, filaments and voids. At redshift
zero, we find that 49 per cent of the dark matter and 23 per cent of the baryons are within
haloes more massive than the resolution limit of 2 × 108 M⊙. The filaments of the cosmic
web host a further 45 per cent of the dark matter and 46 per cent of the baryons. The remaining
31 per cent of the baryons reside in voids. The majority of these baryons have been transported
there through active galactic nuclei feedback. We note that the feedback model of Illustris
is too strong for heavy haloes, therefore it is likely that we are overestimating this amount.
Categorizing the baryons according to their density and temperature, we find that 17.8 per cent
of them are in a condensed state, 21.6 per cent are present as cold, diffuse gas, and 53.9 per cent
are found in the state of a warm–hot intergalactic medium.
We report the discovery of spiral galaxies that are as optically luminous as elliptical brightest cluster
galaxies, with r-band monochromatic luminosity Lr = 8 14L (4:3 7:5 1044 erg s 1). These
super spiral galaxies are also giant and massive, with diameter D = 57 134 kpc and stellar mass
Mstars = 0:3 3:4 1011M. We nd 53 super spirals out of a complete sample of 1616 SDSS
galaxies with redshift z < 0:3 and Lr > 8L. The closest example is found at z = 0:089. We use
existing photometry to estimate their stellar masses and star formation rates (SFRs). The SDSS
and WISE colors are consistent with normal star-forming spirals on the blue sequence. However, the
extreme masses and rapid SFRs of 5 65M yr 1 place super spirals in a sparsely populated region
of parameter space, above the star-forming main sequence of disk galaxies. Super spirals occupy a
diverse range of environments, from isolation to cluster centers. We nd four super spiral galaxy
systems that are late-stage major mergers{a possible clue to their formation. We suggest that super
spirals are a remnant population of unquenched, massive disk galaxies. They may eventually become
massive lenticular galaxies after they are cut o from their gas supply and their disks fade.
Os astrônomos descobriram um processo único sobre como as maiores galáxias elípticas do universo continuam gerando estrelas muito tempo depois do anos de pico de nascimentos estelares. A alta resolução e a sensibilidade à radiação ultravioleta do Hubble, permitiu aos astrônomos observarem nós brilhantes de estrelas azuis, quentes, se formando juntamente com jatos de buracos negros ativos encontrados nos centros das gigantescas galáxias elípticas.
Combinando dados do Huubble com observações feitas por um conjunto de telescópios baseados tanto em Terra como no espaço, duas equipes independentes descobriram que os jatos dos buracos negros, e as estrelas recém-nascidas são todos partes de um ciclo auto-regulado. Jatos de alta energia atirados do buraco negro aquecem um halo de gás circulante, controlando a taxa com a qual o gás esfria e cai na galáxia.
“Pense no gás ao redor da galáxia como uma atmosfera”, explicou o líder do primeiro estudo, Megan Donahue, da Universidade Estadual do Michigan. “Essa atmosfera pode conter material em diferentes estados, do mesmo modo que a nossa atmosfera tem gás, nuvens e chuva. O que nós estamos vendo é um processo parecido com uma tempestade. À medida que os jatos impulsionam o gás para fora do centro da galáxia, parte do gás esfria e precipita em aglomerados frios que caem de volta para o centro da galáxia como gotas de chuvas”.
“As gotas de chuva eventualmente esfriam o suficiente para tornar-se nuvens de formação de estrelas de gás frio molecular, e a capacidade de observar no ultravioleta distante do Hubble, nos permitiu observar diretamente esses chuviscos de formação de estrelas”, explicou o líder do segundo estudo, Grant Tremblay, da Universidade de Yale. “Nós sabemos que esses chuviscos estão linkados com os jatos, pois eles foram encontrados em filamentos que se dobram ao redor dos jatos, ou abraçam as bordas de bolhas gigantes que os jatos inflaram”, disse Tremblay. “E eles terminam fazendo um redemoinho de gás de formação de estrelas ao redor do buraco negro central”.
The physical conditions_in_a_pre_super_star_cluster_molecular_cloud_in_the_an...Sérgio Sacani
Artigo descreve estudo feitos pelos astrônomos utilizando o ALMA para descobrir um proto-aglomerado globular de estrelas gigantes se formando no interior das galáxias Antenas, o famoso par de galáxias em interação. É a primeira vez que os astrônomos conseguem observar um objeto desse tipo nos seus estágios iniciais de vida e com o ambiente ao redor inalterado.
Evidence for an intermediate-mass black hole in the globular cluster NGC 6624Sérgio Sacani
PSR B1820−30A is located in the globular cluster NGC 6624 and is the closest known pulsar
to the centre of any globular cluster. We present more than 25 yr of high-precision timing
observations of this millisecond pulsar and obtain four rotational frequency time derivative
measurements. Modelling these higher order derivatives as being due to orbital motion, we find
solutions that indicate the pulsar is in either a low-eccentricity (0.33 e 0.4) smaller orbit
with a low-mass companion (such as a main-sequence star, white dwarf, neutron star or stellar
mass black hole) or a high-eccentricity (e 0.9) larger orbit with a massive companion. The
cluster mass properties and the observed properties of 4U 1820−30 and the other pulsars in
the cluster argue against the low-eccentricity possibility. The high-eccentricity solution reveals
that the pulsar is most likely orbiting around an intermediate-mass black hole (IMBH) of mass
>7500 M located at the cluster centre. A gravitational model for the globular cluster, which
includes such a central BH, predicts an acceleration that is commensurate with that measured
for the pulsar. It further predicts that the model-dependent minimum mass of the IMBH is
∼60 000 M. Accounting for the associated contribution to the observed period derivative
indicates that the γ -ray efficiency of the pulsar should be between 0.08 and 0.2. Our results
suggest that other globular clusters may also contain central BHs and they may be revealed by
the study of new pulsars found sufficiently close to their centres.
Detection of anisotropic satellite quenching in galaxy clusters up to z ∼ 1Sérgio Sacani
Satellite galaxies in the cluster environment are more likely to be quenched than galaxies in the general field. Recently, it has
been reported that satellite galaxy quenching depends on the orientation relative to their central galaxies: satellites along the
major axis of centrals are more likely to be quenched than those along the minor axis. In this paper, we report a detection
of such anisotropic quenching up to z ∼ 1 based on a large optically selected cluster catalogue constructed from the Hyper
Suprime-Cam Subaru Strategic Program. We calculate the quiescent satellite galaxy fraction as a function of orientation angle
measured from the major axis of central galaxies and find that the quiescent fractions at 0.25 < z < 1 are reasonably fitted
by sinusoidal functions with amplitudes of a few per cent. Anisotropy is clearer in inner regions (<r200m) of clusters and not
significant in cluster outskirts (>r200m). We also confirm that the observed anisotropy cannot be explained by differences in
local galaxy density or stellar mass distribution along the two axes. Quiescent fraction excesses between the two axes suggest
that the quenching efficiency contributing to the anisotropy is almost independent of stellar mass, at least down to our stellar
mass limit of M∗ = 1 × 1010 M. Finally, we argue that the physical origins of the observed anisotropy should have shorter
quenching time-scales than ∼ 1 Gyr, like ram-pressure stripping, because, for anisotropic quenching to be observed, satellites
must be quenched before their initial orientation angles are significantly changed.
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
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
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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.
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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
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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
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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.
A tale of scale & speed: How the US Navy is enabling software delivery from l...sonjaschweigert1
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Today, after several years of existence, an extremely active community and an ultra-dynamic ecosystem, Kubernetes has established itself as the de facto standard in container orchestration. Thanks to a wide range of managed services, it has never been so easy to set up a ready-to-use Kubernetes cluster.
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https://arxiv.org/abs/2306.08302
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The software team must secure its software delivery process to avoid vulnerability and security breaches. This needs to be achieved with existing tool chains and without extensive rework of the delivery processes. This talk will present strategies and techniques for providing visibility into the true risk of the existing vulnerabilities, preventing the introduction of security issues in the software, resolving vulnerabilities in production environments quickly, and capturing the deployment bill of materials (DBOM).
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Paper: https://eprint.iacr.org/2023/1886
In the rapidly evolving landscape of technologies, XML continues to play a vital role in structuring, storing, and transporting data across diverse systems. The recent advancements in artificial intelligence (AI) present new methodologies for enhancing XML development workflows, introducing efficiency, automation, and intelligent capabilities. This presentation will outline the scope and perspective of utilizing AI in XML development. The potential benefits and the possible pitfalls will be highlighted, providing a balanced view of the subject.
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Alma observations of_feed_and_feedback_in_nearby_seyfert_galaxies
1. c ESO 2013
Astronomy & Astrophysics manuscript no. nugas1
September 17, 2013
ALMA observations of feeding and feedback in nearby Seyfert
galaxies: an AGN-driven outflow in NGC 1433 ⋆
F. Combes1 , S. Garc´a-Burillo2 , V. Casasola3 , L. Hunt4 , M. Krips5 , A. J. Baker6 , F. Boone7 , A. Eckart8 , I. Marquez9 , R.
ı
Neri5 , E. Schinnerer10 , and L. J. Tacconi11
1
2
3
4
5
6
7
8
9
10
11
Observatoire de Paris, LERMA (CNRS:UMR8112), 61 Av. de l’Observatoire, F-75014, Paris, France e-mail:
francoise.combes@obspm.fr
´
Observatorio Astron omico Nacional (OAN)-Observatorio de Madrid, Alfonso XII, 3, 28014-Madrid, Spain
INAF – Istituto di Radioastronomia & Italian ALMA Regional Centre, via Gobetti 101, 40129, Bologna, Italy
INAF - Osservatorio Astrofisico di Arcetri, Largo E. Fermi, 5, 50125, Firenze, Italy
IRAM, 300 rue de la Piscine, Domaine Universitaire, F-38406 Saint Martin d’H` res, France
e
Dep. of Physics & Astronomy, Rutgers, the State University of New Jersey, 136 Frelinghuysen road, Piscataway, NJ 08854, USA
CNRS, IRAP, 9 Av. colonel Roche, BP 44346, 31028, Toulouse Cedex 4, France
¨
I. Physikalisches Institut, Universit¨ t zu K¨ ln, Z¨ lpicher Str. 77, 50937, Koln, Germany
a
o
u
Instituto de Astrofsica de Andaluc´a (CSIC), Apdo 3004, 18080 Granada, Spain
ı
Max-Planck-Institut f¨ r Astronomie (MPIA), K¨ nigstuhl 17, 69117 Heidelberg, Germany
u
o
¨
Max-Planck-Institut f¨ r extraterrestrische Physik, Giessenbachstr. 1, Garching bei M unchen, Germany
u
Received 2013/ Accepted 2013
ABSTRACT
We report ALMA observations of CO(3-2) emission in the Seyfert 2 galaxy NGC 1433 at the unprecedented spatial resolution of
′′
0. 5 = 24 pc. Our aim is to probe AGN (active galactic nucleus) feeding and feedback phenomena through the morphology and
dynamics of the gas inside the central kpc. NGC 1433 is a strongly barred spiral with 3 resonant rings: one at the ultra-harmonic
resonance near corotation, and the others at outer and inner Lindblad resonances (OLR and ILR). A nuclear bar of 400 pc radius
is embedded in the large-scale primary bar. The CO map, which covers the whole nuclear region (nuclear bar and ring), reveals a
nuclear gaseous spiral structure, inside the nuclear ring encircling the nuclear stellar bar. This gaseous spiral is well correlated with
the dusty spiral seen in HST images. The nuclear spiral winds up in a pseudo-ring at ∼200 pc radius, which might correspond to the
inner ILR. Continuum emission is detected at 0.87 mm only at the very center, and its origin is more likely thermal dust emission
than non-thermal emission from the AGN. It might correspond to the molecular torus expected to exist in this Seyfert 2 galaxy. The
HCN(4-3) and HCO+ (4-3) lines were observed simultaneously, but only upper limits are derived, with a ratio to the CO(3-2) line
lower than 1/60 at 3σ, indicating a relatively low abundance of very dense gas. The kinematics of the gas over the nuclear disk reveal
rather regular rotation only slightly perturbed by streaming motions due to the spiral; the primary and secondary bars are too closely
aligned with the galaxy major or minor axes to leave a signature in the projected velocities. Near the nucleus, there is an intense
high-velocity CO emission feature redshifted to 200 km/s (if located in the plane), with a blue-shifted counterpart, at 2′′ (100 pc)
from the center. While the CO spectra are quite narrow in the center, this wide component is interpreted as an outflow, involving a
molecular mass of 3.6 106 M⊙ , and a flow rate ∼ 7 M⊙ /yr. The flow could be in part driven by the central star formation, but mainly
boosted by the AGN through its radio jets.
Key words. Galaxies: active — Galaxies: Individual: NGC 1433 — Galaxies: ISM — Galaxies: kinematics and dynamics —
Galaxies: nuclei — Galaxies: spiral
1. Introduction
It is now observationally well established that supermassive
black holes (SMBHs) reside in the nuclei of all galaxies with
massive spheroids in the Local Universe and at higher redshifts
as well (e.g. Kormendy & Ho 2013). Quasars at high redshift and
Seyfert nuclei locally are fueled by accretion of material onto the
SMBH. Although much progress has been made on both theoretical and observational fronts in the last decade, the relationship
of black hole growth with galaxy formation and evolution is still
far from being completely understood.
One of the outstanding problems is to identify the mechanism that drives gas from the disk towards the nucleus, removSend offprint requests to: F. Combes
⋆
Based on observations carried out with ALMA in Cycle 0.
ing its large angular momentum, to feed the central black hole
and trigger the nuclear activity. Theoretically, broad-brush solutions have been found; cosmological simulations rely on mergerdriven gas inflow via bar instabilities to feed a central starburst and fuel the SMBH (e.g., Hopkins et al. 2006; di Matteo
et al. 2008). Nevertheless, in the Local Universe, no clear correlation has been found between the presence of an active galactic
nucleus (AGN) and either companions or the presence of bars
(see e.g. Combes 2003, 2006, Jogee 2006 for reviews). It is possible that locally the relation between these large-scale phenomena and the duty cycle of nuclear fueling is masked by different
timescales. Indeed, the presence of resonant rings, vestiges of a
previous bar, appears to be correlated with Seyfert activity (Hunt
& Malkan 1999). Also it could be that gas inflow is not always
possible because of dynamical barriers (e.g., nuclear rings, see
Piner et al. 1995; Regan & Teuben 2004).
1
2. F. Combes et al.: CO in NGC 1433
To assess potential inhibitors of the ubiquitous gas inflow assumed in simulations, we must examine the nuclear kinematics
around local AGN. This can be best done with molecular tracers, since in galaxy centers, HI is typically converted to molecular gas. CO line emission is therefore our best probe, and in
particular CO(3-2), which traces the high density gas (10 4 -105
cm−3 ) in the dense AGN circumnuclear regions (as we have
shown in Boone et al. 2011). HCN and HCO+ line emission
should trace the densest material (at least 107 cm−3 ), and diagnose its excitation and chemistry. We have undertaken during the last decade the NUGA (NUclei of GAlaxies) program
to study the gas distributions in nearby AGN, and find clues to
their fueling. In the dozen nearby Seyfert or LINER galaxies observed with the IRAM Plateau de Bure interferometer (PdBI)
in CO(2-1), we achieved a spatial resolution of 50-100 pc, and
frequently worse for the most distant galaxies. In these galaxies, a large variety of gas distributions have been found; however we detected on-going AGN feeding at 0.1-1 kpc scales
for only 5/12 cases: NGC 2782 (Hunt et al. 2008, bar triggered
by an interaction), NGC 3147 (Casasola et al. 2008), NGC 3627
(Casasola et al. 2011), NGC 4579 (Garc`a-Burillo et al. 2009),
ı
and NGC 6574 (Lindt-Krieg et al. 2008). The most common
feeding mechanism in these galaxies appears to be kinematically
decoupled embedded bars, i.e. the combination of a slowly rotating kpc-scale stellar bar (or oval) and a kinematically decoupled
nuclear bar, with overlapping dynamical resonances. Such resonances and kinematic decoupling are fostered by a large central
mass concentration and high gas fraction. The gas is first stalled
in a nuclear ring (a few 100 pc scale), and then driven inward
under the influence of the decoupled nuclear bar. However, because of insufficient resolution, our previous observations were
most of the time unable to probe the gas within 100 pc of the
AGN.
In this paper, we present ALMA Cycle 0 observations in the
CO(3-2) line of the Seyfert 2 NGC 1433, where the beam is 24 pc
in size. The nearby distance (9.9 Mpc) and low inclination of 33◦
make NGC 1433 an ideal target to test and refine the scenario of
AGN feeding and feedback, and constrain BH models which are
only now beginning to examine in detail gas structures within
100 pc (Hopkins & Quataert 2010; Perez-Beaupuits et al. 2011).
Up to now, resolution of tens of pc scales has been obtained only in a few Seyfert galaxies, and only in hot or warm
gas tracers. The best example is NGC 1068, the most nearby
Seyfert 2 prototype, where near-IR H 2 lines have been mapped
′′
with SINFONI at 0. 075 resolution (5.2pc) by M¨ ller-Sanchez
u
et al. (2009). The behavior of this hot (1000-2000K) gas is
not yet settled however; while an outflow model is proposed
by Galliano & Alloin (2002), and a warped disk model by
¨
Schinnerer et al. (2000), Muller-Sanchez et al. (2009) propose
a strong inflow model. Krips et al. (2011) explain their SMA
′′
CO(3-2) map at 0. 6 = 40 pc resolution by a rotating disk plus
an outflow of the disk gas due to shocks and/or a circumnuclear
disk-jet interaction. Thus, gas inflow could fuel the AGN at a 10pc scale, and the jet-gas interaction could simultaneously drag
gas outwards on scales of hundreds of pc. The presence of an
outflow in the circumnuclear disk of NGC 1068 has also been
suggested to be responsible of the large-scale molecular shocks
revealed by strong SiO emission in this galaxy (Garc`a- Burillo
ı
et al 2010). The outflow is clearly seen in ALMA data (Garc`aı
Burillo et al. 2013, in prep.). Typical outflow velocities are found
of the order of 200 km/s in NGC 1068.
An important ingredient in cosmological simulations is feedback, which can regulate SMBH growth and suppress star formation (e.g., Croton et al. 2006, di Matteo et al. 2008, and
2
Table 1. Basic data for the NGC 1433 galaxy
Parameter
Valueb
Referencec
a
h
m
s
αJ2000
03 42 01.55
(1)
δJ2000 a
-47◦ 13′ 19.5′′
(1)
Vhel
1075 km s−1
(1)
RC3 Type
(R’)SB(r)ab
(1)
Nuclear Activity
Seyfert 2
(2)
◦
Inclination
33. 0
(3)
Position Angle
199◦ ± 1◦
(3)
Distance
9.9 Mpc (1′′ = 48 pc) (4)
LB
1.0 × 1010 L⊙
(4)
MH I
5.5 × 108 M⊙
(5)
MH 2
2.3 × 108 M⊙
(6)
Mdust (60 and 100 µm) 2.5 × 106 M⊙
(7)
LFIR
1.3 × 109 L⊙
(7)
αJ2000 d
03h 42m 01.49 s
New center
δJ2000 d
-47◦ 13′ 20.2′′
New center
a
(αJ2000 , δJ2000 ) is the phase tracking center of our 12 CO interferometric observations
b
Luminosity and mass values extracted from the literature have
been scaled to the distance of D = 9.9 Mpc.
c
(1)
NASA/IPAC
Extragalactic
Database
(NED,
http://nedwww.ipac.caltech.edu/); (2) Veron-Cetty & Veron (1986);
(3) Buta et al. (2001); (4) HyperLeda; (5) Ryder et al. (1996);
(6) Bajaja et al. (1995), reduced to the conversion factor 2.3
1020 cm−2 /(Kkm/s); (7) IRAS Catalog.
d
New adopted center, coinciding with the continuum peak.
references therein). Molecular observations can constrain specific feedback mechanisms, by discovering molecular outflows
through their high velocity wings, and determine their origin (star formation or AGN), through high resolution observations. Chung et al. (2011) showed the ubiquitous presence of
1000 km/s molecular outflows in starbursts with SFRs larger
than 100 M⊙ /yr (see also Feruglio et al. 2010, Fischer et al. 2010,
Sturm et al. 2011). The CO emission in the high velocity wings
may generally represent 25% of the total observed emission.
In NGC 1068 the outflow, if present, is only of the order of
200 km/s and entrained by the radio jet. Coil et al. (2011) also
find that galactic winds are frequent in ionized gas lines, in
post-starburst and AGN host galaxies at 0.2<z<0.8, but they
are low velocity winds, likely due to supernovae. High velocity winds, driven by an AGN, might be frequent in molecular gas (Leon et al. 2007, Feruglio et al. 2010, 2013, Alatalo
et al. 2011, Nesvadba et al. 2011, Dasyra & Combes 2012, Aalto
et al. 2012, Spoon et al. 2013, Veilleux et al. 2013), as well as in
the ionized or atomic gas component (Rupke et al. 2005; Riffel
& Storchi-Bergmann 2011). In Arp 220, Sakamoto et al. (2009)
have discovered 100-200 km/s outflows, through P-Cygni profiles in HCO+ (3-2), HCO+ (4-3) and CO(3-2) along the line of
sight to the nucleus. They interpret this gas as driven outwards by
the nuclear starburst. Because NGC 1433 is not an IR-luminous
starburst, it is unlikely that an AGN wind close to the nucleus
would be swamped by a starburst wind, thus facilitating its identification with ALMA’s high resolution.
1.1. NGC 1433
NGC 1433 is a nearby active barred galaxy, member of the
Dorado group which includes 26 galaxies (Kilborn et al. 2005).
We selected it from a sample of low-luminosity AGN spirals already detected in CO emission, for its proximity, and moderate
3. F. Combes et al.: CO in NGC 1433
Fig. 1. Channel maps of CO(3-2) emission in the center of NGC 1433. Each of the 42 square boxes is 20′′ in size, while the primary beam is
18′′ in diameter . Channels are separated by 4.24 km/s. They are plotted from 978 (top left) to 1152 km/s (bottom right, the panels are labelled in
′′
′′
frequency). The synthesized beam is 0. 56×0. 42 (PA=85◦ ). The center of the maps is the phase center of the interferometric observations given in
Table 1. The color scale is linear, between 1 and 30 mJy/beam.
Table 2. Main dynamical features in NGC 1433
Feature
Nuclear bar
Nuclear ring
Primary bar
Inner ring
Outer ring
Radius
9′′ (430 pc)
9.5′′ (460 pc)
83′′ (4 kpc)
108′′ (5.2 kpc)
190′′ (9.1 kpc)
PA(◦ )
31
31
94
95
15
inclination. It has been classified as Seyfert 2 by Veron-Cetty &
Veron (1986), for its strong nuclear emission lines and its high
[NII]/Hα ratio. However, Sosa-Brito et al. (2001) prefer to classify it as LINER, because of its [OIII]/Hβ ratio, which is just at
the limit between Seyfert and LINERs. Liu & Bregman (2005)
detect the nuclear point source in X-rays with ROSAT.
The galaxy has a rich network of dusty filaments around the
nucleus. Its morphology reveals conspicuous rings (Buta 1986,
Buta et al. 2001); the presence of nuclear, inner and outer rings
has motivated its nickname of the “Lord of Rings” (Buta &
Combes 1996). Table 2 presents the sizes and orientation of
the main dynamical features. NIR images have revealed a nuclear bar inside the nuclear ring, of radius ∼400 pc (Jungwiert
et al. 1997). The ring is the site of a starburst and is patchy in
UV (continuum HST image from Maoz et al. 1996). 31 compact
sources contribute 12% of the UV light. Inside the ring the dust
traces a flocculent or multiple-arm nuclear spiral structure (HST
image from Peeples & Martini 2006). There is a peak of 6 mJy
in radio continuum emission at 843 MHz in the center (Harnett
1987), with a weak extension along the bar. The HI 21cm emission map (Ryder et al. 1996) reveals that the atomic gas is concentrated in the inner and outer rings, with some depletion in
the nuclear ring and bar region. In contrast, the central region
is filled with molecular hydrogen (Bajaja et al. 1995, CO SEST
map). Our ALMA single pointing includes in its field-of-view
(FOV) all the nuclear bar and nuclear spiral gas.
2. Observations
The observations were carried out with the Atacama Large
Millimeter/submillimeter Array (ALMA) telescope in Cycle 0,
with 19 antennae, during june and july 2012. NGC 1433 was observed simultaneously in CO(3-2), HCO+ (4-3), HCN(4-3), and
continuum, with Band 7. The sky frequencies were 344.56 GHz,
355.46 GHz, 353.24 GHz and 343.27 GHz respectively. The observations were done in 3 blocks, with a total duration of 2 hours.
For each period, NGC 1433 was observed for 27 minutes; the
median system temperatures were T sys = 140, 230 and 160 K.
The observations were centered on the nucleus, with a single
pointing covering a FOV of 18′′ . The Cycle 0 extended config′′
′′
uration provides in Band 7 a beam of 0. 56×0. 42, with a PA of
85◦ . The galaxy was observed in dual polarization mode with
1.875 GHz total bandwidth per baseband, and a velocity resolu3
4. F. Combes et al.: CO in NGC 1433
Table 3. CO(3-2) line fluxes, after primary beam correction
Line
Total
C1
C2
C3
Blue(2)
Red(2)
SCO
Jy km/s
234± 1
103± 2
105± 4
26± 3
6.0± 0.1
10.1± 0.1
Vhel
km/s
1073.1±0.3
1040.0±0.4
1089.1±0.2
1123.0±4.0
1018.7±0.6
1138.2±0.3
∆V(1)
km/s
85.3± 0.7
46.± 1
30.± 1
59.± 5
61.± 1
56.± 0.7
Peak flux
Jy
2.58
2.1
3.3
0.4
0.09
0.17
Total = Gaussian fit, assuming only one component, C1/C1/C3 represent 3 velocity-component decomposition
(1)
Full Width at Half Maximum FWHM
(2)
Fits for the blue and red components of the outflow, summed
′′
′′
over a region 0. 7×1. 2 each (cf Fig 9).
Almost no CO(3-2) emission was detected outside the FullWidth Half-Power (FWHP) primary beam. Due to missing short
spacings, extended emission was filtered out at scales larger than
∼3′′ in each channel map. The elongated features detected, corresponding to the dust lanes, along arms and rings are, however,
quite narrow (thinner than 2 ′′ as in HST images), so the missingflux problem might not be severe in individual velocity slices.
Low level negative sidelobes adjacent to bright emission were
however observed.
3. Results
Fig. 2. Velocity field (top) and integrated intensity (bottom) of the
CO(3-2) emission in the center of NGC 1433. Coordinates are RADec in arcsec relative to the phase center (see Table 1). The color scale
ranges are in km/s relative to 1075 km/s (top) and in Jy/beam.MHz (or
′′
′′
0.87 Jy/beam.km/s) at the bottom. The beam size of 0. 56×0. 42 is indicated at the bottom left. The phase center is a pink cross, and the new
adopted center is the red cross, in the bottom panel.
tion of 0.488 MHz ∼0.42 km/s. The spectra were then smoothed
to 4.88 MHz (4.24 km/s) to build channel maps.
This choice of correlator configuration, selected to observe simultaneously three lines, provided a velocity range of
1600 km/s for each line, but not centered (200km/s on one side
and 1400 km/s on the other) which is adequate for a nearly faceon galaxy, and 1800 MHz bandwidth in the continuum. The total
integration time provided an rms of 0.09 mJy/beam in the continuum, and ∼3 mJy/beam in the line channel maps (corresponding
to ∼170 mK, at the obtained spatial resolution). The flux calibration was done with the nearby quasar J0334-401, which is
regularly monitored at ALMA, and resulted in 10% accuracy.
The data were calibrated, and cleaned using first a mask at
the 50 mJy emission level, and then the 30 mJy level. The fi′′
nal cube has 360x360 pixels with 0. 1 per pixel in the plane
of the sky, and 60 channels of 4.24 km/s width. The data were
calibrated, imaged and cleaned with the CASA software (v3.3;
McMullin et al. 2007), and the analysis was then finalized with
the GILDAS software (Guilloteau & Lucas 2000).
The final maps were corrected for primary beam attenuation to compute fluxes, but were kept uncorrected for the plots.
4
Figure 1 displays 42 of the CO(3-2) channel maps, with a velocity range of 175 km/s and a velocity resolution of 4.24 km/s.
The velocity field is rather regular, although perturbed by the
tightly-wound spiral structure (see also Fig. 2). At the outermost
channels, the emission at the highest velocities does not occur
primarily at large radii, but mainly towards the center.
3.1. Molecular gas distribution and morphology
To measure fluxes we used a clipped cube where all pixel values <2σ (6 mJy/beam) were set to zero. The mean intensity is
plotted in Fig. 2 (bottom). Since the galaxy is more extended
than the primary beam, it is difficult to quantify the missing
flux. We compare to the central spectrum obtained with a single dish in Sect. 3.4. However, these observations were obtained
with the SEST in CO(1-0) with a 43′′ beam. Nevertheless, our
FOV encompasses the entire nuclear ring, and the emission in
this nuclear region has by far the strongest surface density at
many wavelengths (Buta et al. 2001, Comeron et al. 2010; Ho
et al. 2011).
We superposed the CO map onto the HST maps in the B,
V and I filters. All show a remarkable similarity in morphology, as displayed in Figure 3. The features are so distinct that
they were used to align the HST images, which suffered from
an inexact astrometry. The CO emission nicely corresponds to
the dust lanes, interleaved with the bright regions. The gas and
the dust are intimately mixed, and reveal a multi-arm structure
with a low pitch angle. There is not a well-defined density-wave
here, but rather a more flocculent spiral structure with multiple
branches. The structure is easily appreciated, thanks to the low
inclination of the galaxy (33◦ , Table 1). This spiral structure is
entirely included inside the nuclear ring, of ∼ 10′′ =0.5 kpc in
radius (Buta et al. 2001, see Table 2).
5. F. Combes et al.: CO in NGC 1433
Fig. 5. Overlay of CO(3-2) contours on the 0.87mm continuum image.
The FOV is 6′′ in diameter. The yellow star shows the phase center of
Table 1, while the peak of the continuum is our new adopted center. The
colour palette unit is mJy.
Fig. 3. Top: Overlay of CO(3-2) contours on the unsharp-masked blue
(F450W) HST image. The HST image has been aligned to correspond to
the ALMA astrometry. Bottom: Unsharp masking of the HST I-image
of NGC 1433, covering the nuclear ring and the dust lanes along the
primary bar. The FWHP of the primary beam is indicated in yellow
(18′′ in diameter), and the FOV of the CO map in Fig. 2 and in the above
′′
image is indicated in blue (square of 24. 8 on a side). The characteristic
dust lanes on the leading edge of the main bar are outlined in orange.
What is remarkable is the large difference between the
gas complex morphology in this nuclear region, revealed by
ALMA and the already known smoother stellar morphology
(Buta et al. 2001). The lower panel of Fig. 3 shows an unsharpmasked red image of the nuclear region, embedded in the primary bar whose leading dust lanes are marked. As is frequently
found in strong primary bars of early-type spirals, the dust lanes
wind up onto the nuclear ring, which corresponds to the inner
Lindblad resonance, and a secondary nuclear bar has decoupled
inside (e.g. Buta & Combes 1996). However, the gas does not
follow the stellar nuclear ring, but instead is flowing through a
flocculent spiral onto an even smaller nuclear ring, of ∼200pc radius, and from there reaches the very center, at least at the 20pc
scale, our resolution.
The molecular gas morphology reveals notable asymmetries:
for instance the peak of CO emission is not in the center but in
a NE cloud complex, at about 4′′ from the center (200 pc), with
no SW counterpart. In the very center, the emission extends 2 ′′
to the SW, but with a corresponding hole in the NE. This might
indicate an m = 1 Fourier component, in addition to the m = 2
and m = 3 arm features. To determine whether one particular m
component dominates, we have computed the Fourier decomposition of the 2D gas density, once the galaxy disk has been deprojected to the sky plane 1 . Fig. 4 displays the face-on molecular
gas distribution. The pseudo-ring at radius ∼4′′ corresponding
to 200 pc is clearly visible and nearly round. We have computed
the radial distribution of the various Fourier components, normalized to the axi-symmetric power. The surface density of the
gas has been decomposed as:
am (r)cos(mφ − φm (r))
Σ(r, φ) = Σ0 (r) +
m
Fig. 4. Deprojection of the CO emission towards a face-on disk, centered on the new adopted center of Table 1. The pseudo-ring of 4 ′′ radius, here underlined with a black circle, is standing out, nearly round.
and the amplitude of the various Fourier components m are normalized as Am (r) = am (r)/Σ0 (r). As a result, all Am (r) coefficients show noisy behaviours, at a maxium amplitude of 0.5, but
there is no particular dominance of any m feature.
1
The decomposition is performed using the new center defined in
Sect. 3.2.
5
6. F. Combes et al.: CO in NGC 1433
3.2. Continuum emission
Besides the CO(3-2) line, continuum emission was detected at
0.87mm. For that, the fourth band of width 468.8 MHz was used,
with a rms noise level of 0.15 mJy. Fig. 5 displays the CO(3-2)
contours superposed onto the continuum map. The peak emission is just detected at 3σ, about 0.5 mJy. The emission is ex′′
tended in the East-West direction, its size is 1′′ x 0. 5.
3.2.1. Recentring
To establish the origin of the continuum emission, one issue is
to determine the exact position of the AGN. We observed with
a phase center corresponding to the peak of the near-infrared
emission of the stellar component, which is known only within
′′
0. 7 uncertainty (e.g. 2MASS catalog, 2003). The HST maps, in
B, V and I would be precise enough, but they are all affected by
dust obscuration. In particular there is a conspicuous dust-lane
extending nearly horizontally in the SW. The continuum emis′′
′′
sion peaks at a position (-0. 6, -0. 7) with respect to our phase
center, so perfectly compatible within the uncertainty. This position is however better centered with respect to the CO emission.
We therefore choose to adopt the peak of the continuum emission as the new center. The latter is also perfectly compatible
with the position of the X-ray nuclear point source seen by Liu
& Bregman (2005). Although the AGN might not correspond exactly to the peak of the stellar component, it is possible that our
new center is also the correct position of the AGN and the supermassive black hole. But it is unclear whether or not the 0.87 mm
AGN synchrotron emission is detected.
3.2.2. Slope of radio-continuum emission
Radio continuum emission has been detected at 35 cm by
Harnett (1987) with a resolution of 43′′ ×58′′ ; the emission is
extended, and shows 6 mJy in the central beam. NGC 1433 has
also been observed at 21 cm with ATCA by Ryder et al. (1996),
with a spatial resolution of 30′′ . The central emission is 3.4 mJy,
quite similar to what is obtained at the ends of the bar from the
HII regions. Since the whole nuclear region is included in their
central beam, it is possible that all the radio emission comes from
star formation in the ring or nuclear region (both synchrotron
from supernovae, and free-free emission). The continuum becomes 2 mJy at 4.8 GHz, with no polarisation (Stil et al. 2009).
Comparing the central fluxes at 21cm and 0.87mm, the slope
of the radio spectrum would be -0.35, which could be a mixture of synchrotron with a steeper spectrum (−0.7), and freefree emission with slope −0.1. Both steep radio spectra (Sadler
et al. 1995), and flat ones (Ulvestad & Ho 2001) have been found
in Seyfert spiral galaxies, so it is not possible to conclude on the
AGN contribution in the center. From the Hα flux it would be
possible in principle to estimate the fraction of free-free emission expected in the center, but the spatial resolution (2′′ ) is not
enough to disentangle what is coming actually from the very
center. Also the extinction might be a problem.
3.2.3. Dust continuum emission
Another possibility is that the continuum is coming from thermal dust emission. At millimeter wavelengths, we are nearly in
the Rayleigh-Jeans domain, and the dust emission is only proportional to the dust temperature. Continuum dust emission is
then expected to be quite similar in morphology to the CO(3-2)
emission (e.g. Dumke et al. 1997). Why is this not the case? The
6
difference might be due to the lack of short spacing data, and the
filtering out of the diffuse extended continuum emission. Indeed,
the continuum is much more sensitive to this problem than the
line emission. From the IRAS fluxes, the average temperature
of the dust in NGC 1433 can be estimated as 24 K, assuming
that the dust opacity has a dependence in frequency of νβ , with
β = 2. This is similar to central dust temperatures observed in
∼40′′ beams with Herschel in star-forming barred galaxies such
as NGC 3627 (Hunt et al. 2013, in prep.). From a flux of 0.5
mJy/beam, and assuming the same Draine & Lee (1984) dust
absorption cross section as described in Dumke et al. (1997) for
a solar metallicity, we find a molecular gas column density of
N(H2 ) = 4.5 1022 cm−2 , over a beam of 24 pc in size. This is
what is expected from a typical Giant Molecular Cloud. In comparison, in the same position, the CO(3-2) emission is about 4
Jy km/s, for a CO integrated intensity in one beam of 262 K km/s,
corresponding to N(H2 ) = 6 1022 cm−2 , with a standard conversion factor of 2.3 1020 cm−2 /(K km/s) (e.g. Solomon & Vanden
Bout 2005). Considering all the uncertainties, the continuum
emission is at the level expected from dust alone. Given that dust
emission is only detected at the very center, it might be possible
that this dust is associated with the molecular torus expected to
hide the AGN in this Seyfert 2 galaxy. The derived mass of the
torus would be 9 105 M⊙ . Since the dust in the torus is certainly
warmer than in the disk, this might also explain why the continuum emission is not more extended, like the CO, in addition
to the interferometer’s filtering argument explained above. Midinfrared maps with ISO at 7 and 15µm show also a high central
concentration, but with low resolution (Roussel et al. 2001).
Only high-resolution observations with ALMA at several
different frequencies would be able to settle the origin of the continuum emission, and determine whether the AGN is detected
directly.
3.3. CO kinematics: a molecular outflow?
In a previous paper (Buta et al. 2001), a detailed mass model
of NGC 1433 has been performed, from NIR photometry and
Hα spectroscopy. Rotational and epicyclic frequencies (Ω and
κ) were then derived, and together with the numerical simulations from Buta & Combes (2000), the predictions of the resonance locations, compared to the observed ring radii, favored a
pattern speed of 23 km/s/kpc (or 26 km/s/kpc with our slightly
different distance adopted). With this pattern speed, there are two
inner Lindblad resonances (ILRs), located at 3.6 and 30′′2 . The
existence of two ILRs weakens the primary bar, and allows the
decoupling of a secondary bar, with a higher pattern speed (e.g.
Friedli & Martinet 1993, Buta & Combes 1996). The nuclear bar
produces negative torques on the gas, previously stalled at the
nuclear ring, and provides a dynamical way to fuel the nucleus.
This process has been simulated in detail in Hunt et al. (2008),
and shows how the gas in the nuclear ring progressively flows to
the center, in a spiral structure, and in a ring shrinking in radius.
It appears that this scenario applies quite well to NGC 1433: its
nuclear ring lies between the two ILRs, and the molecular gas
morphology reveals an accumulation of the gas at the inner ILR.
This configuration strongly suggests that the gas is presently fueling the AGN.
The top panel of Figure 2 displays the velocity field of the
molecular gas. The velocity field is well described by rotation,
2
Treuthardt et al. (2008) propose a lower value for the pattern speed
in NGC 1433, 18 km/s/kpc, but their simulation shows a nuclear ring
much larger in size than observed.
7. F. Combes et al.: CO in NGC 1433
with the same position angle as the HI velocity field at larger
scales (Ryder et al. 1996) and consistent with the Hα central
kinematics (Buta et al. 2001). There are no strong perturbations
to this regular rotation due to streaming motions in a barred potential, since the major axis of the galaxy is aligned with the
minor axis of the primary bar, and also with the nuclear bar (see
Fig. 3). The amplitude of the rotation is low but compatible with
the observed Hα velocities within 10′′ in radius, given the low
inclination of 33◦ . The rotation velocities deduced from the CO
kinematics are plotted in comparison to the Hα rotation curve in
Fig. 6.
Fig. 6. Top:Rotational velocity model adopted for NGC 1433, based on
the Hα kinematics (red filled squares) from Buta et al. (2001), compatible with the CO rotation curve (green filled hexagons). The CO velocity
field is however sparsely sampled. Bottom: Velocity residuals after subtraction of a regular rotation model, based on the Hα rotation curve
above. The map has been recentered on the new adopted center of Table
1. The two orthogonal lines indicate the position of the PV diagrams of
Fig 7.
There is however a noticeable redshifted perturbation located
in the very center and extending to the south-west between 0 and
2′′ i.e. 100 pc in extent. To better isolate this feature, we plot
the position-velocity diagram along the major axis of the galaxy
in the top of Fig. 7. This slice reveals gas jumping by almost
100 km/s in projection, at much higher velocity than the rest of
the nuclear disk gas. There is also a noticeable blue-shifted counterpart, at a distance from the center of about 2 ′′ (100 pc) towards
the north-west, which is conspicuous in the position-velocity diagram along the minor-axis of the galaxy in the bottom of Fig.
7. In this direction, both flow components are seen, while the
largest gradient of velocities is along PA= 135◦ , which might be
the projected direction of the flow.
Fig. 7. Top: Position-velocity diagram along the major axis of PA =
199◦ (east is at left). The central outflow is clearly visible superposed
on the smooth rotational velocity gradient (underlined by the yellow
line, corresponding to the rotation curve of Fig. 6). Bottom: Positionvelocity diagram, along the minor axis, of PA = 109◦ (East is at left).
The two components (red and blue) of the outflow are visible, along a
slice, where the velocity should be equal to the systemic one (yellow
line).
Another way to compare these peculiar velocities to the rest
of the nuclear region in 2D, is to subtract the expected regular
velocity field known from the Hα gas in the same region. Fig.
6 displays the residuals obtained, relative to the adopted Hα rotation curve, plotted above. The figure shows the ionized gas
7
8. F. Combes et al.: CO in NGC 1433
rotation curve deduced by Buta et al. (2001). The derived CO
velocities, although in sparse regions, are compatible with this
adopted rotation curve. The stellar velocity, once corrected by a
large asymmetric drift, appears higher (Buta et al. 2001). The gas
then does not follow the maximum circular velocity. This might
be due to substantial gas turbulence, and/or to an overestimation
of the correction of the stellar velocity.
The peculiar velocity of the gas at the nucleus and northwest of the center is clearly seen in the residuals of Fig. 6. If
the gas were in the plane, the deprojected velocity could be as
high as 200 km/s, but other orientations with respect to the sky
plane are possible. Let us call α the angle between the outflow
direction and the line of sight. The observed velocity in projection is Vout f low cos(α), and the extend of the flow in the plane of
the sky is Rout f low sin(α). It is likely that α is not close to the extreme values, i.e. zero or 90 degrees, since the observed outflow
velocity and the projected size of the outflow are both subtantial, i.e. respectively ∼ 100 km/s and ∼ 100 pc. This means that
tan(α) is of the order of 1. The flow is aligned roughly with the
minor axis, and if it was orthogonal to the plane, tan(α)=0.6.
We think, however, that the outflow is not orthogonal, since we
are seing the galaxy inclined by 33◦ on the sky, and the near
side is the NW, from the winding sense of the spiral arms, assumed trailing. The outflow cannot be exactly perpendicular to
the disk, unless the blue and red regions would be inverted. The
flow must at least be inclined by an angle > 33◦ from the normal to the plane. Conservatively, the outflow velocity likely lies
between 100 km/s and 200 km/s.
This high-velocity gas is also noticeable in the total spectrum, obtained by summing the signal over the field-of-view, as
in Fig. 8. A Gaussian decomposition in three components has
been performed on the spectrum, and the results displayed in
Table 3. The high-velocity red component represents nearly 5%
of the total. The blue-velocity counterpart is diluted in the normal rotational component C1 (part of the two-horn profile characteristic of rotation).
Fig. 8. Total CO(3-2) spectrum, integrated over the observed map, with
a FOV of 18′′ , after correction for primary beam attenuation. The vertical scale is in Jy. The green line is the result of the Gaussian fit with 3
velocity components; see Table 3.
8
Finally, the high-velocity red component is best located in
the map through the individual spectra of Fig. 9, where all spec′′
tra are shown within a radius of 2. 5. Although in principle, this
high velocity gas could be inflowing as well as outflowing, we
consider inflow to be unlikely. Indeed, there is no other signature of violent perturbation due to a companion nearby, and if
gas were slowly accreted to fuel the AGN, it would first have
settled into the rotational frame at much larger radii than the last
100 pc.
To better estimate the quantity of gas in the outflow, we have
′′
′′
summed the CO flux within 2 regions of sizes 0. 7×1. 2, centered
on the red and blue outflow regions, taking into account the primary beam correction (cf Fig 9). The results are given in Table
3. Assuming the standard CO-to-H2 conversion factor (see next
Section). we derive molecular masses of 1.3 106 and 2.3 106 M⊙
for the blue and red velocity components, respectively.
Is the outflow also detected in the ionized gas? There is no
outflow detected in X-rays, but there is not enough spatial resolution to see it anyway. In Hα maps and spectroscopy, it is hard
to reach a conclusion, even from the best velocity field obtained
from Fabry-Perot interferometry by Buta (1986). In his Fig. 8,
we can see a quite perturbed velocity field inside the central 20′′ ,
which may reflect steep gradients. However, the spatial resolution is only 2′′ , while the projected distance between our red
and blue outflow peak components is roughly the same. An outflow of ionized gas is however quite compatible with the data.
The non detection of ionized gas outflow in galaxies showing a
molecular outflow is also found in other compact systems like
NGC 1377 (Aalto et al. 2012). A comparison with other molecular outflows will be discussed in Section 4.
3.4. CO luminosity, H2 mass and HCO+ /HCN upper limits
Figure 8 displays the total CO(3-2) spectrum, integrated over
the entire observed map after correction for primary beam attenuation. When integrated over the line (FWHM=85.3 km/s),
the integrated emission is 234± 1 Jy km/s. Towards the central
position, Bajaja et al. (1995) found a CO(1-0) spectrum peaking at T∗ = 48mK, with FWHM=168 km/s, yielding a total inA
tegrated flux of 193 Jy km/s, in a beam of 43′′ . Unfortunately,
no CO(2-1) spectra have been reported. We can however remark
that the CO(1-0) flux corresponds to a larger region than the one
observed here (as witnessed by the broader linewidth), and our
CO(3-2) flux is an upper limit of the expected CO(1-0) flux in
a 18′′ beam, since at low J the flux increases with the J-level.
We can therefore safely conclude that the CO(3-2)/CO(1-0) ratio must be significantly larger than 2 in flux density units: the
CO gas is relatively excited, meaning that the average density
is at least of the order of 104 cm−3 . Assuming a CO(3-2)/CO(10) flux ratio of ∼5, similar to that observed in the star-forming
nuclei of nearby galaxies (e.g. Matsushita et al. 2004, Boone
et al. 2011), the CO detected inside our primary beam, at the
distance of 9.9 Mpc, corresponds to a molecular mass M(H2 ) =
5.2 107 M⊙ , with the standard CO-to-H2 conversion factor of 2.3
1020 cm−2 /(Kkm/s). By comparison, Bajaja et al. (1995) find in
their central 43′′ beam a mass of 1.8 108 M⊙ , covering an area
5.7 larger.
As far as the CO outflow is concerned, the use of any CO-toH2 conversion factor is uncertain. Let us then try to get a strict
minimum of the mass in using the hypothesis of optically thin
emission. Within this hypothesis, we can write the column density of CO in the upper state of the (3-2) transition as:
N J=3 = 6.41013 ICO(3−2)
9. F. Combes et al.: CO in NGC 1433
′′
Fig. 9. CO(3-2) spectra within 2. 5 of the center. The velocity scale is from 960 to 1190 km/s (corresponding to -115 to 115 km/s with respect to
the systemic velocity). The vertical scale is from 1 to 40 mJy. The new adopted center is marked with a black star (the map coordinates are with
respect to the phase center). The red velocity component can be seen at the new center and just above, and the blue velocity component is centered
′′
′′
at (-2, 0.5). The two regions 0. 7×1. 2 each, selected to integrate the outflow mass in Table 3 are indicated by red and blue rectangles respectively.
The corresponding integrated spectra are plotted in the insert (scale in Jy).
where ICO(3−2) is the integrated (3-2) emission in K.km/s. The
total CO column density is then obtained, using the ratio
N J=3 /NCO =
5
exp(−E J=3 /kT ex )
Q
where E J=3 is the energy in the upper level of the (3-2) transition, Q the partition function = 0.36 T ex , and T ex the excitation temperature, assumed constant over all J levels. The N(H2 )
column density is then derived, assuming a CO abundance of
6 10−5 (e.g. Glover & Mac Low 2011). Comparing the N(H2 )
values obtained within the optically thick hypothesis, and the
use of the standard conversion factor, we found column densities less by factors 27, 71 and 83 when T ex = 10, 20 and 30K
respectively. Over the red outflow region large as 3-4 beams, we
found N(H2 ) ∼ 5 1022 cm−2 , while the optically thin hypothesis
will lead to values as low as 6 1020 cm−2 . We estimate that such
low values are not realistic, however, since the mean volumetric
density over the region will be ∼ 1 cm−3 , and not 100 cm−3 , the
minimum required to excite CO emission. Note that the mean
CO(3-2) brightness temperature observed within the flow region
if 3K, so that the surface filling factor of the molecular component cannot be much smaller than 0.1. Since the critical density
of the CO(3-2) line is 105 cm−3 , the optically thin hypothesis is
very unlikely to provide any emission, even taking into account
the surface filling factor.
Finally, our simultaneous observations of HCO+ (4-3) and
HCN(4-3) yielded only negative results. We can better derive
significant upper limits towards the CO emission maxima. Over
the whole map, there were 160 pixels (equivalent to 8 beams)
with CO(3-2) emission larger than 60 times the 3σ upper limits in HCO+ (4-3) and HCN(4-3), assuming the same linewidth.
In all CO maxima, an intensity ratio between CO and the highdensity tracers >60 means that the average density of the gas in
the multiple-arm flocculent spiral is not high. The critical density to excite the HCO+ (4-3) and HCN(4-3) molecular lines is at
least 107 cm−3 .
9
10. F. Combes et al.: CO in NGC 1433
4. Discussion and summary
We have presented our first ALMA results for a Seyfert 2 galaxy
from our extended NUGA sample, NGC 1433. The observations
in CO(3-2) allow us to reach an unprecedented spatial resolution
of 24 pc, even with the limited Cycle 0 capabilities.
The morphology of the CO emission comes as a surprise.
Although the Seyfert 2-type would suggest the presence of a
thick obscuring component in front of the nucleus, there is no
large concentration of molecular gas in the center, but instead a
widely distributed multiple-arm spiral of CO emission, all over
the nuclear ring region. The dense gas tracers HCO + and HCN
remain undetected, confirming the absence of very dense gas
(density larger than 107 cm−3 ).
Although infrared images reveal the presence of a stellar
nuclear bar inside the nuclear ring (of radius 0.5 kpc), located
near the inner Lindblad resonances (e.g. Buta et al. 2001), the
gas does not follow the nuclear bar. Instead the gas appears to
flow inward and partly accumulate in a ring-like structure at
a radius ∼ 200 pc, which coincides with the inner ILR (IILR)
as computed by Buta et al. (2001). This is indeed expected
at some epochs of self-consistent N-body+hydro simulations,
when the gas enters an inflowing phase inside two ILRs (e.g.
Hunt et al. 2008). The gas is not stalled in this pseudo-ring, but
continues to flow in towards the very center.
The kinematics of the CO emission are dominated by a
rather regular rotational velocity field, with only slight perturbations from the multiple-arm spiral. No strong streaming motion is imprinted on these kinematics by the primary and nuclear bars, since their axes coincide with the galaxy major axis.
Additionally, two peculiar features appear at high velocity, one
red-shifted component towards the center within 100 pc, and a
blue-shifted counterpart at 2′′ (100 pc) from the center. The amplitude of these components is up to about 100 km/s in projection
(∼ 200 km/s if in the galaxy plane). Given their location near the
nucleus, we tentatively interpret these high-velocity features as
the two sides of an outflow. Globally, these features represent as
much as ∼ 7% of the total molecular emission, in the nuclear
ring region, i.e., 3.6 x 106 M⊙ .
It is not likely that these peculiar high-velocity features reflect strong streaming motions due to a dynamical perturbation,
since there is no such perturbation in the center. The gas is not
following the nuclear bar, which is rather weak. Is a central mass
able to generate such a high rotation in the center? Considering
that the blue and red components are separated in projection
along the minor axis by 2′′ = 100 pc, or about 120 pc in the
plane of the galaxy, a massive black hole located in the center, at
R=60pc from each component, should have a mass of at least
MBH =V2 R/G, for the rotational velocity in the galaxy plane
V=200km/s, or M BH =5.6 108 M⊙ . This would make NGC 1433
a strong outlier to the M BH − σ relation; indeed from the bulge
mass, we would expect the BH mass to be 5 106 M⊙ , e.g., Buta
(1986). In any case, for gas rotating in circular motion, within
the sphere of influence of the black hole, the velocity maxima
should appear on the major axis and disappear on the minor axis,
contrary to what is observed here. Another solution would be to
assume the existence of a mini-polar disk, with completely different orientation than the main disk, and almost edge-on, but no
galaxy interaction or accretion event support this hypothesis.
The origin of the outflow might be related to star formation,
which is concentrated in the nuclear ring region. The star formation rate (SFR) can be estimated from the far infrared luminosity, as calibrated by Kennicutt (1998). From the IRAS
fluxes, the FIR luminosity is 1.3 109 L⊙ (Table 1), and the SFR
10
equals 0.2 M⊙ /yr. From the Hα luminosity, measured at 3.7 1040
erg/s by Hameed & Devereux (2005), we can also deduce from
Kennicutt’s calibration, a SFR = 0.29 M⊙ /yr, which is quite compatible.
The order of magnitude of the mass outflow rate can be computed, using our estimates for the molecular mass in the highvelocity components (Table 3), as M=3.6 106 M⊙ . This mass
has been obtained using the standard CO-to-H2 conversion factor, since there is no reason a priori to adopt the lower factor
applying to ULIRGs. Cicone et al. (2012) show in Mrk231 that
the molecular gas in the galaxy and the outflowing gas share the
same excitation. However, this mass could be an upper limit, if
the flow is made of more diffuse gas. Since each high-velocity
component has a projected radial extent from the center of d=1′′
∼ 50 pc, and moves at a projected velocity of v=100 km/s, the
flow rate is of the order of dM/dt ∼ (Mv/d) tanα= 7 tanα M⊙ /yr,
with α being the angle between the outflow and the line of sight.
Although this estimate is uncertain by a factor of a few, given
the unknown α, it is about 40 times higher than the SFR; since
galactic winds due to starbursts correspond in general to mass
outflows of the same order as the SFR (e.g. Veilleux et al. 2005),
we conclude that the outflow is not likely due to star formation
alone, and is at least helped by the AGN. We note that starburst
winds are generally observed in galaxies with SFR larger than 5
M⊙ /yr, and SFR surface densities larger than 10 −3 M⊙ /yr/kpc2 .
NGC 1433 has a low total SFR ∼ 0.2 M⊙ /yr, however, its SFR
surface density is 0.34 M⊙ /yr/kpc2 , if we assume that the whole
SFR is confined to the nuclear disk of 9′′ radius. The SFR surface
density would therefore be enough to drive a wind, although (as
noted above) the mass loading factor expected for this type of
wind would still be considerably lower than what we observe in
NGC 1433.
The kinetic luminosity of the flow can be estimated as Lkin
=0.5 dM/dt v2 =2.3 tanα (1+ tan2 α) 1040 erg/s. The luminosity
of the AGN can be estimated at various wavelengths. Although
the X-ray point source is weak, 1.7 1039 erg/s over 0.3-8kev (Liu
& Bregman 2005), we can derive a bolometric luminosity of
the AGN from optical and NIR magnitudes in the central aperture (Buta et al. 2001) of 1.3 1043 erg/s. From the expected BH
mass of 5 106 M⊙ , if NGC 1433 is on the MBH − σ relation, the
Eddington luminosity is 6.3 1044 erg/s. The kinetic luminosity
of the outflow is low with respect to the bolometric luminosity
of the AGN, making it plausible that the latter is able to power
the wind.
The momentum flux of the outflow, computed by dM/dt v
is however too large with respect to that provided by the AGN
photons LAGN /c, by a factor 2000 tanα/cosα. Although the momentum can be boosted in case of energy-conserved wind by
factors up to 50 (e.g. Faucher-Gigu` re & Quataert 2012), it is
e
more likely that the AGN contributes to drive the outflow not by
its radiation pressure, but through its radio jets. From the central 1.4 GHz power of 3.4mJy detected by Ryder et al. (1996),
we can estimate the jet power, from the formula proposed by
Birzan et al. (2008, their equation 16): P jet = 2 1042 erg/s. Since
this power is about two orders of magnitudes higher than the
kinetic luminosity of the outflow, the jet is amply able to drive
the flow, even with low coupling. The jet interaction with the
interstellar medium has been simulated by Wagner et al. (2012)
who show that the jet is able to drive a flow efficiently, as soon
as the Eddington ratio of the jet P jet /LEdd is larger than 10−4 . In
NGC 1433, this ratio is about 3.2 10−3 .
The molecular outflow in NGC 1433 is one of only a few
discovered recently occuring in low-star forming galaxies, with
relatively weak AGN, where the flow might be driven by both
11. F. Combes et al.: CO in NGC 1433
the starburst and the radio jets. The LINER NGC 6764 has 4.3
106 M⊙ of molecular gas driven out with a velocity of about
100 km/s (Leon et al. 2007). The flow projects to larger distances
than in NGC 1433, and might be more evolved. The outflow rate
is lower, of the order of 1 M ⊙ /yr. NGC 1266 is also a LINER and
has the highest flow rate of 13 M⊙ /yr, with 2.4 107 M⊙ of molecular gas driven with V=177 km/s (Alatalo et al. 2011). A third
LINER, with total SFR of ∼ 1 M⊙ /yr, NGC 1377 has an outflow
rate of 8 M⊙ /yr, an outflowing mass of 1.1 107 M⊙ , at V=140
km/s (Aalto et al. 2012). All these galaxies have star formation
playing a role in the outflow, but the properties of the flow require the contribution of the AGN, through the entrainement of
its radio jets. The latter is the most needed for NGC 1433, which
has the lowest SFR of all.
This tentative detection of a molecular gas outflow, triggered essentially by the AGN, should be confirmed by higherresolution ALMA observations. The detection of a radio continuum component at the very center, which might be due to
thermal dust emission from a molecular torus, also deserves a
higher-resolution study.
Acknowledgements. We warmly thank the referee for constructive comments
and suggestions. The ALMA staff in Chile and ARC-people at IRAM are
gratefully acknowledged for their help in the data reduction. We particularly
thank Gaelle Dumas and Philippe Salom´ for their useful advice. We used
e
observations made with the NASA/ESA Hubble Space Telescope, and obtained from the Hubble Legacy Archive, which is a collaboration between
the Space Telescope Science Institute (STScI/NASA), the Space Telescope
European Coordinating Facility (ST-ECF/ESA) and the Canadian Astronomy
Data Centre (CADC/NRC/CSA). F.C. acknowledges the European Research
Council for the Advanced Grant Program Num 267399-Momentum. I.M. acknowledges financial support from the Spanish grant AYA2010-15169 and from
the Junta de Andalucia through TIC-114 and the Excellence Project P08-TIC03531. We made use of the NASA/IPAC Extragalactic Database (NED), and of
the HyperLeda database.
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