分类： 天文学 >> 天文学 提交时间： 2023-02-19
Aritra Ghosh
C. Megan Urry
Aayush Mishra
Laurence Perreault-Levasseur
Priyamvada Natarajan
David B. Sanders
Daisuke Nagai
Chuan Tian
Nico Cappelluti
Jeyhan S. Kartaltepe
Meredith C. Powell
Amrit Rau
Ezequiel Treister
摘要： We use the Galaxy Morphology Posterior Estimation Network (GaMPEN) to estimate morphological parameters and associated uncertainties for $\sim 8$ million galaxies in the Hyper Suprime-Cam (HSC) Wide survey with $z \leq 0.75$ and $m \leq 23$. GaMPEN is a machine learning framework that estimates Bayesian posteriors for a galaxy's bulge-to-total light ratio ($L_B/L_T$), effective radius ($R_e$), and flux ($F$). By first training on simulations of galaxies and then applying transfer learning using real data, we trained GaMPEN with $<1\%$ of our dataset. This two-step process will be critical for applying machine learning algorithms to future large imaging surveys, such as the Rubin-Legacy Survey of Space and Time (LSST), the Nancy Grace Roman Space Telescope (NGRST), and Euclid. By comparing our results to those obtained using light-profile fitting, we demonstrate that GaMPEN's predicted posterior distributions are well-calibrated ($\lesssim 5\%$ deviation) and accurate. This represents a significant improvement over light profile fitting algorithms which underestimate uncertainties by as much as $\sim60\%$. For an overlapping sub-sample, we also compare the derived morphological parameters with values in two external catalogs and find that the results agree within the limits of uncertainties predicted by GaMPEN. This step also permits us to define an empirical relationship between the S\'ersic index and $L_B/L_T$ that can be used to convert between these two parameters. The catalog presented here represents a significant improvement in size ($\sim10 \times $), depth ($\sim4$ magnitudes), and uncertainty quantification over previous state-of-the-art bulge+disk decomposition catalogs. With this work, we also release GaMPEN's source code and trained models, which can be adapted to other datasets.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Michael J. Koss
Ezequiel Treister
Darshan Kakkad
J. Andrew Casey-Clyde
Taiki Kawamuro
Jonathan Williams
Adi Foord
Benny Trakhtenbrot
Franz E. Bauer
George C. Privon
Claudio Ricci
Richard Mushotzky
Loreto Barcos-Munoz
Laura Blecha
Thomas Connor
Fiona Harrison
Tingting Liu
Macon Magno
Chiara M. F. Mingarelli
Francisco Muller-Sanchez
摘要： We present multi-wavelength high-spatial resolution (~0.1'', 70 pc) observations of UGC 4211 at z=0.03474, a late-stage major galaxy merger at the closest nuclear separation yet found in near-IR imaging (0.32'', ~230 pc projected separation). Using Hubble Space Telescope/STIS, VLT/MUSE+AO, Keck/OSIRIS+AO spectroscopy, and ALMA observations, we show that the spatial distribution, optical and NIR emission lines, and millimeter continuum emission are all consistent with both nuclei being powered by accreting supermassive black holes (SMBHs). Our data, combined with common black hole mass prescriptions, suggests that both SMBHs have similar masses, log MBH~8.1 (south) and log MBH~8.3 (north), respectively. The projected separation of 230 pc (~6X the black hole sphere of influence) represents the closest-separation dual AGN studied to date with multi-wavelength resolved spectroscopy and shows the potential of nuclear (<50 pc) continuum observations with ALMA to discover hidden growing SMBH pairs. While the exact occurrence rate of close-separation dual AGN is not yet known, it may be surprisingly high, given that UGC 4211 was found within a small, volume-limited sample of nearby hard X-ray detected AGN. Observations of dual SMBH binaries in the sub-kpc regime at the final stages of dynamical friction provide important constraints for future gravitational wave observatories.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Alessandro Peca
Nico Cappelluti
Meg Urry
Stephanie LaMassa
Stefano Marchesi
Tonima Ananna
Mislav Baloković
David Sanders
Connor Auge
Ezequiel Treister
Meredith Powell
Tracey Jane Turner
Allison Kirkpatrick
Chuan Tian
摘要： We present X-ray spectral analysis of XMM and Chandra observations in the 31.3 deg$^2$ Stripe-82X (S82X) field. Of the 6181 X-ray sources in this field, we analyze a sample of 2937 active galactic nuclei (AGN) with solid redshifts and sufficient counts determined by simulations. Our results show a population with median values of spectral index $\Gamma=1.94_{-0.39}^{+0.31}$, column density log$\,N_{\mathrm{H}}/\mathrm{cm}^{-2}=20.7_{-0.5}^{+1.2}$ and intrinsic, de-absorbed, 2-10 keV luminosity log$\,L_{\mathrm{X}}/\mathrm{erg\,s}^{-1}=44.0_{-1.0}^{+0.7}$, in the redshift range 0-4. We derive the intrinsic fraction of AGN that are obscured ($22\leq\mathrm{log}\,N_{\mathrm{H}}/\mathrm{cm}^{-2}43$. This work constrains the AGN obscuration and spectral shape of the still uncertain high-luminosity and high-redshift regimes (log$\,L_{\mathrm{X}}/\mathrm{erg\,s}^{-1}>45.5$, $z>3$), where the obscured AGN fraction rises to $64\pm12\%$. We report a luminosity and density evolution of the X-ray luminosity function, with obscured AGN dominating at all luminosities at $z>2$ and unobscured sources prevailing at log$\,L_{\mathrm{X}}/\mathrm{erg\,s}^{-1}>45$ at lower redshifts. Our results agree with evolutionary models in which the bulk of AGN activity is triggered by gas-rich environments and in a downsizing scenario. Also, the black hole accretion density (BHAD) is found to evolve similarly to the star formation rate density, confirming the co-evolution between AGN and host-galaxy, but suggesting different time scales in their growing history. The derived BHAD evolution shows that Compton-thick AGN contribute to the accretion history of AGN as much as all other AGN populations combined.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We present a study of the molecular gas distribution and kinematics in the cicumnuclear region (radii $\lesssim 2\,$kpc) of the $z\approx0.061$ quasar I$\,$Zwicky$\,$1 using a collection of available Atacama Large Millimeter/submillimeter Array (ALMA) observations of the carbon monoxide (CO) emission. With an angular resolution of $\sim0.36''$ (corresponding to $\sim\,400\,\rm pc$), the host galaxy sub-structures including the nuclear molecular gas disk, spiral arms, and a compact bar-like component are resolved. We analyzed the gas kinematics based on the CO image cube and obtained the rotation curve and radial distribution of velocity dispersion. The velocity dispersion is about $30\,\rm km\,s^{-1}$ in the outer CO disk region and rises up to $\gtrsim 100\,\rm km\,s^{-1}$ at radius $\lesssim 1\,$kpc, suggesting that the central region of disk is dynamically hot. We constrain the CO-to-$\rm H_2$ conversion factor, $\alpha_{\rm CO}$, by modeling the cold gas disk dynamics. We find that, with prior knowledge about the stellar and dark matter components, the $\alpha_{\rm CO}$ value in the circumnuclear region of this quasar host galaxy is $1.55_{-0.49}^{+0.47}\,M_\odot\,\left(\rm K\,km\,s^{-1}\,pc^2\right)^{-1}$, which is between the value reported in ultra-luminous infrared galaxies and in the Milky-Way. The central 1$\,$kpc region of this quasar host galaxy has significant star formation activity, which can be identified as a nuclear starburst. We further investigate the high velocity dispersion in the central region. We find that the ISM turbulent pressure derived from the gas velocity dispersion is in equilibrium with the weight of the ISM. This argues against extra power from AGN feedback that significantly affects the kinematics of the cold molecular gas.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We present a study of the molecular gas distribution and kinematics in the cicumnuclear region (radii $\lesssim 2\,$kpc) of the $z\approx0.061$ quasar I$\,$Zwicky$\,$1 using a collection of available Atacama Large Millimeter/submillimeter Array (ALMA) observations of the carbon monoxide (CO) emission. With an angular resolution of $\sim0.36''$ (corresponding to $\sim\,400\,\rm pc$), the host galaxy sub-structures including the nuclear molecular gas disk, spiral arms, and a compact bar-like component are resolved. We analyzed the gas kinematics based on the CO image cube and obtained the rotation curve and radial distribution of velocity dispersion. The velocity dispersion is about $30\,\rm km\,s^{-1}$ in the outer CO disk region and rises up to $\gtrsim 100\,\rm km\,s^{-1}$ at radius $\lesssim 1\,$kpc, suggesting that the central region of disk is dynamically hot. We constrain the CO-to-$\rm H_2$ conversion factor, $\alpha_{\rm CO}$, by modeling the cold gas disk dynamics. We find that, with prior knowledge about the stellar and dark matter components, the $\alpha_{\rm CO}$ value in the circumnuclear region of this quasar host galaxy is $1.55_{-0.49}^{+0.47}\,M_\odot\,\left(\rm K\,km\,s^{-1}\,pc^2\right)^{-1}$, which is between the value reported in ultra-luminous infrared galaxies and in the Milky-Way. The central 1$\,$kpc region of this quasar host galaxy has significant star formation activity, which can be identified as a nuclear starburst. We further investigate the high velocity dispersion in the central region. We find that the ISM turbulent pressure derived from the gas velocity dispersion is in equilibrium with the weight of the ISM. This argues against extra power from AGN feedback that significantly affects the kinematics of the cold molecular gas.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Mengyuan Xiao
David Elbaz
Carlos Gómez-Guijarro
Lucas Leroy
Longji Bing
Emanuele Daddi
Benjamin Magnelli
Maximilien Franco
Luwenjia Zhou
Mark Dickinson
Tao Wang
Wiphu Rujopakarn
Georgios E. Magdis
Ezequiel Treister
Hanae Inami
Ricardo Demarco
Mark T. Sargent
Xinwen Shu
Jeyhan S. Kartaltepe
David M. Alexander
摘要： Our current understanding of the cosmic star formation history at z>3 is primarily based on UV-selected galaxies (i.e., LBGs). Recent studies of H-dropouts have revealed that we may be missing a large proportion of star formation that is taking place in massive galaxies at z>3. In this work, we extend the H-dropout criterion to lower masses to select optically dark/faint galaxies (OFGs), in order to complete the census between LBGs and H-dropouts. Our criterion (H> 26.5 mag & [4.5] 3 (z_med=4.1) in the GOODS-ALMA field, covering a wide distribution of stellar masses with log($M_{\star}$/$M_{\odot}$) = 9.4-11.1. We find that up to 75% of the OFGs with log($M_{\star}$/$M_{\odot}$) = 9.5-10.5 were neglected by previous LBGs and H-dropout selection techniques. After performing stacking analyses, the OFGs exhibit shorter gas depletion timescales, slightly lower gas fractions, and lower dust temperatures than typical star-forming galaxies. Their SFR_tot (SFR_ IR+SFR_UV) is much larger than SFR_UVcorr (corrected for dust extinction), with SFR_tot/SFR_UVcorr = $8\pm1$, suggesting the presence of hidden dust regions in the OFGs that absorb all UV photons. The average dust size measured by a circular Gaussian model fit is R_e(1.13 mm)=1.01$\pm$0.05 kpc. We find that the cosmic SFRD at z>3 contributed by massive OFGs is at least two orders of magnitude higher than the one contributed by equivalently massive LBGs. Finally, we calculate the combined contribution of OFGs and LBGs to the cosmic SFRD at z=4-5 to be 4 $\times$ 10$^{-2}$ $M_{\odot}$ yr$^{-1}$Mpc$^{-3}$, which is about 0.15 dex (43%) higher than the SFRD derived from UV-selected samples alone at the same redshift.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Mengyuan Xiao
David Elbaz
Carlos Gómez-Guijarro
Lucas Leroy
Longji Bing
Emanuele Daddi
Benjamin Magnelli
Maximilien Franco
Luwenjia Zhou
Mark Dickinson
Tao Wang
Wiphu Rujopakarn
Georgios E. Magdis
Ezequiel Treister
Hanae Inami
Ricardo Demarco
Mark T. Sargent
Xinwen Shu
Jeyhan S. Kartaltepe
David M. Alexander
摘要： Our current understanding of the cosmic star formation history at z>3 is primarily based on UV-selected galaxies (i.e., LBGs). Recent studies of H-dropouts have revealed that we may be missing a large proportion of star formation that is taking place in massive galaxies at z>3. In this work, we extend the H-dropout criterion to lower masses to select optically dark/faint galaxies (OFGs), in order to complete the census between LBGs and H-dropouts. Our criterion (H> 26.5 mag & [4.5] 3 (z_med=4.1) in the GOODS-ALMA field, covering a wide distribution of stellar masses with log($M_{\star}$/$M_{\odot}$) = 9.4-11.1. We find that up to 75% of the OFGs with log($M_{\star}$/$M_{\odot}$) = 9.5-10.5 were neglected by previous LBGs and H-dropout selection techniques. After performing stacking analyses, the OFGs exhibit shorter gas depletion timescales, slightly lower gas fractions, and lower dust temperatures than typical star-forming galaxies. Their SFR_tot (SFR_ IR+SFR_UV) is much larger than SFR_UVcorr (corrected for dust extinction), with SFR_tot/SFR_UVcorr = $8\pm1$, suggesting the presence of hidden dust regions in the OFGs that absorb all UV photons. The average dust size measured by a circular Gaussian model fit is R_e(1.13 mm)=1.01$\pm$0.05 kpc. We find that the cosmic SFRD at z>3 contributed by massive OFGs is at least two orders of magnitude higher than the one contributed by equivalently massive LBGs. Finally, we calculate the combined contribution of OFGs and LBGs to the cosmic SFRD at z=4-5 to be 4 $\times$ 10$^{-2}$ $M_{\odot}$ yr$^{-1}$Mpc$^{-3}$, which is about 0.15 dex (43%) higher than the SFRD derived from UV-selected samples alone at the same redshift.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We combine Atacama Large Millimeter/submillimeter Array and Multi Unit Spectroscopic Explorer observations tracing the molecular gas, millimeter continuum, and ionized gas emission in six low-redshift ($z \lesssim 0.06$) Palomar-Green quasar host galaxies to investigate their ongoing star formation at $\sim$kpc-scale resolution. The AGN contribution to the cold dust emission and the optical emission-line flux is carefully removed to derive spatial distributions of the star formation rate (SFR), which, complemented with the molecular gas data, enables the mapping of the depletion time ($t_{\rm dep}$). We report ubiquitous star formation activity within the quasar host galaxies, with the majority of the ongoing star formation occurring in the galaxy center. The rise of the star formation rate surface density ($\Sigma_{\rm SFR}$) toward the nucleus is steeper than that observed for the cold molecular gas surface density, reaching values up to $\Sigma_{\rm SFR} \approx 0.15-0.80\,M_\odot\,$yr$^{-1}\,$kpc$^{-2}$. The gas in the nuclear regions is converted into stars at a shortened depletion time ($t_{\rm dep} \approx 0.2-2.0\,$Gyr), suggesting that those zones can be deemed as starbursts. At large galactocentric radius, we find that the ongoing star formation takes place within spiral arms or H$\,$II region complexes, with an efficiency comparable to that reported for nearby inactive spirals ($t_{\rm dep} \approx 1.8\,$Gyr). We find no evidence of star formation activity shutoff in the PG quasar host galaxies. On the contrary, these observations shed light on how the central environments of galaxies hosting actively accreting supermassive black holes builds up stellar mass.
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