- ID:
- ivo://CDS.VizieR/J/ApJ/701/587
- Title:
- A deep HST H-band imaging survey. II. QUEST QSOs
- Short Name:
- J/ApJ/701/587
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results from a deep Hubble Space Telescope (HST) NICMOS H-band imaging survey of 28 z<0.3 QSOs from the Palomar-Green (PG) sample. This program is part of QUEST (Quasar/ULIRG Evolution Study) and complements a similar set of data on 26 highly nucleated ULIRGs presented in Paper I (Veilleux et al. 2006ApJ...643..707V). Our analysis indicates that the fraction of QSOs with elliptical hosts is higher among QSOs with undetected far-infrared (FIR) emission, small infrared excess (L_IR_/L_B_<10), and luminous hosts. The hosts of FIR-faint QSOs show a tendency to have less pronounced merger-induced morphological anomalies and larger QSO-to-host luminosity ratios on average than the hosts of FIR-bright QSOs, consistent with late-merger evolution from FIR-bright to FIR-faint QSOs.
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- ID:
- ivo://CDS.VizieR/J/ApJ/787/108
- Title:
- Age estimates for massive SFR stellar populations
- Short Name:
- J/ApJ/787/108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A major impediment to understanding star formation in massive star-forming regions (MSFRs) is the absence of a reliable stellar chronometer to unravel their complex star formation histories. We present a new estimation of stellar ages using a new method that employs near-infrared (NIR) and X-ray photometry, Age_JX_. Stellar masses are derived from X-ray luminosities using the L_X_-M relation from the Taurus cloud. J-band luminosities are compared to mass-dependent pre-main-sequence (PMS) evolutionary models to estimate ages. Age_JX_ is sensitive to a wide range of evolutionary stages, from disk-bearing stars embedded in a cloud to widely dispersed older PMS stars. The Massive Young Star-Forming Complex Study in Infrared and X-ray (MYStIX) project characterizes 20 OB-dominated MSFRs using X-ray, mid-infrared, and NIR catalogs. The Age_JX_ method has been applied to 5525 out of 31784 MYStIX Probable Complex Members. We provide a homogeneous set of median ages for over 100 subclusters in 15 MSFRs; median subcluster ages range between 0.5 Myr and 5 Myr. The important science result is the discovery of age gradients across MYStIX regions. The wide MSFR age distribution appears as spatially segregated structures with different ages. The Age_JX_ ages are youngest in obscured locations in molecular clouds, intermediate in revealed stellar clusters, and oldest in distributed populations. The NIR color index J-H, a surrogate measure of extinction, can serve as an approximate age predictor for young embedded clusters.
- ID:
- ivo://CDS.VizieR/J/ApJ/750/91
- Title:
- Ages and metallicities of old stellar systems
- Short Name:
- J/ApJ/750/91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a statistical analysis of the properties of a large sample of dynamically hot old stellar systems, from globular clusters (GCs) to giant ellipticals, which was performed in order to investigate the origin of ultracompact dwarf galaxies (UCDs). The data were mostly drawn from Forbes et al. (2008, Cat. J/MNRAS/389/1924). We recalculated some of the effective radii, computed mean surface brightnesses and mass-to-light ratios, and estimated ages and metallicities. We completed the sample with GCs of M31. We used a multivariate statistical technique (K-Means clustering), together with a new algorithm (Gap Statistics) for finding the optimum number of homogeneous sub-groups in the sample, using a total of six parameters (absolute magnitude, effective radius, virial mass-to-light ratio, stellar mass-to-light ratio, and metallicity). We found six groups. FK1 and FK5 are composed of high- and low-mass elliptical galaxies, respectively. FK3 and FK6 are composed of high-metallicity and low-metallicity objects, respectively, and both include GCs and UCDs. Two very small groups, FK2 and FK4, are composed of Local Group dwarf spheroidals. Our groups differ in their mean masses and virial mass-to-light ratios. The relations between these two parameters are also different for the various groups. The probability density distributions of metallicity for the four groups of galaxies are similar to those of the GCs and UCDs. The brightest low-metallicity GCs and UCDs tend to follow the mass-metallicity relation like elliptical galaxies. The objects of FK3 are more metal-rich per unit effective luminosity density than high-mass ellipticals.
- ID:
- ivo://CDS.VizieR/J/A+A/541/A118
- Title:
- AGN-Host Galaxy Connection
- Short Name:
- J/A+A/541/A118
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of morphological and colour analysis of X-ray detected AGN in the SXDS field. X-ray data were gathered from the XMM-Newton scientific archive, and were reduced by our team using the standard SAS procedures. The obtained catalogue of 1121 X-ray emitters was cross-matched with the publicly available optical catalogue (Furusawa et al., 2008, Cat. J/ApJS/176/1), using a cross-matched radius of 3 arcsec and obtaining 806 optical counterparts. For these objects the photometric redshifts, K-corrections, morphological, X-ray, and rest-frame colour properties were measured and analysed.
- ID:
- ivo://CDS.VizieR/J/ApJ/691/705
- Title:
- AGN host galaxy morphologies in COSMOS
- Short Name:
- J/ApJ/691/705
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use Hubble Space Telescope/Advanced Camera for Surveys images and a photometric catalog of the Cosmic Evolution Survey (COSMOS) field to analyze morphologies of the host galaxies of ~400 active galactic nucleus (AGN) candidates at redshifts 0.3<z<1.0. We compare the AGN hosts with a sample of nonactive galaxies drawn from the COSMOS field to match the magnitude and redshift distribution of the AGN hosts. We perform two-dimensional surface brightness modeling with GALFIT to yield host galaxy and nuclear point source magnitudes. X-ray-selected AGN host galaxy morphologies span a substantial range that peaks between those of early-type, bulge-dominated and late-type, disk-dominated systems. We also measure the asymmetry and concentration of the host galaxies. Unaccounted for, the nuclear point source can significantly bias results of these measured structural parameters, so we subtract the best-fit point source component to obtain images of the underlying host galaxies. Our concentration measurements reinforce the findings of our two-dimensional morphology fits, placing X-ray AGN hosts between early- and late-type inactive galaxies. AGN host asymmetry distributions are consistent with those of control galaxies.
- ID:
- ivo://CDS.VizieR/J/AJ/146/87
- Title:
- AGN photometry. II. A catalog from the CFHTLS
- Short Name:
- J/AJ/146/87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the second paper of the series Detecting Active Galactic Nuclei Using Multi-filter Imaging Data. In this paper we review shapelets, an image manipulation algorithm, which we employ to adjust the point-spread function (PSF) of galaxy images. This technique is used to ensure the image in each filter has the same and sharpest PSF, which is the preferred condition for detecting AGNs using multi-filter imaging data as we demonstrated in Paper I of this series. We apply shapelets on Canada-France-Hawaii Telescope Legacy Survey Wide Survey ugriz images. Photometric parameters such as effective radii, integrated fluxes within certain radii, and color gradients are measured on the shapelets-reconstructed images. These parameters are used by artificial neural networks (ANNs) which yield: photometric redshift with an rms of 0.026 and a regression R-value of 0.92; galaxy morphological types with an uncertainty less than 2 T types for z<=0.1; and identification of galaxies as AGNs with 70% confidence, star-forming/starburst (SF/SB) galaxies with 90% confidence, and passive galaxies with 70% confidence for z<=0.1. The incorporation of ANNs provides a more reliable technique for identifying AGN or SF/SB candidates, which could be very useful for large-scale multi-filter optical surveys that also include a modest set of spectroscopic data sufficient to train neural networks.
- ID:
- ivo://CDS.VizieR/J/ApJ/678/116
- Title:
- AGNs in nuclear star clusters
- Short Name:
- J/ApJ/678/116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study galaxies that host both nuclear star clusters and AGNs, implying the presence of a massive black hole. We select a sample of 176 galaxies with previously detected nuclear star clusters that range from ellipticals to late-type spirals. We search for AGNs in this sample using optical spectroscopy and archival radio and X-ray data. We find galaxies of all Hubble types and with a wide range of masses (10^9^-10^11^M_{sun}_) hosting both AGNs and nuclear star clusters. From the optical spectra, we classify 10% of the galaxies as AGN and an additional 15% as composite, indicating a mix of AGN and star formation spectra. The fraction of nucleated galaxies with AGNs increases strongly as a function of galaxy and nuclear star cluster mass. For galaxies with both a nuclear star cluster and a black hole, we find that the masses of these two objects are quite similar. However, nondetections of black holes in Local Group nuclear star clusters show that not all clusters host black holes of similar masses. We discuss the implications of our results for the formation of nuclear star clusters and massive black holes.
- ID:
- ivo://CDS.VizieR/J/MNRAS/443/1151
- Title:
- AIMSS Project. I. Compact Stellar Systems
- Short Name:
- J/MNRAS/443/1151
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe the structural and kinematic properties of the first compact stellar systems discovered by the Archive of Intermediate Mass Stellar Systems project. These spectroscopically confirmed objects have sizes (~6<R_e_[pc]<500) and masses (~2x10^6^<M*/M_{sun}_<6x10^9^) spanning the range of massive globular clusters, ultracompact dwarfs (UCDs) and compact elliptical galaxies (cEs), completely filling the gap between star clusters and galaxies. Several objects are close analogues to the prototypical cE, M32. These objects, which are more massive than previously discovered UCDs of the same size, further call into question the existence of a tight mass-size trend for compact stellar systems, while simultaneously strengthening the case for a universal 'zone of avoidance' for dynamically hot stellar systems in the mass-size plane. Overall, we argue that there are two classes of compact stellar systems (1) massive star clusters and (2) a population closely related to galaxies. Our data provide indications for a further division of the galaxy-type UCD/cE population into two groups, one population that we associate with objects formed by the stripping of nucleated dwarf galaxies, and a second population that formed through the stripping of bulged galaxies or are lower mass analogues of classical ellipticals. We find compact stellar systems around galaxies in low- to high-density environments, demonstrating that the physical processes responsible for forming them do not only operate in the densest clusters.
- ID:
- ivo://CDS.VizieR/J/MNRAS/435/3444
- Title:
- ALHAMBRA survey morphological catalogue
- Short Name:
- J/MNRAS/435/3444
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Advanced Large Homogeneous Area Medium Band Redshift Astronomical (ALHAMBRA) is photometric survey designed to trace the cosmic evolution and cosmic variance. It covers a large area of ~4deg^2^ in eight fields, where seven fields overlap with other surveys, allowing us to have complementary data in other wavelengths. All observations were carried out in 20 continuous, medium band (30nm width) optical and 3 near-infrared (JHK) bands, providing the precise measurements of photometric redshifts. In addition, morphological classification of galaxies is crucial for any kind of galaxy formation and cosmic evolution studies, providing the information about star formation histories, their environment and interactions, internal perturbations, etc. We present a morphological classification of >40000 galaxies in the ALHAMBRA survey. We associate to every galaxy a probability to be early type using the automated Bayesian code galsvm. Despite of the spatial resolution of the ALHAMBRA images (~1arcsec), for 22051 galaxies, we obtained the contamination by other type of less than 10 percent. Of those, 1640 and 10322 galaxies are classified as early- (down to redshifts ~0.5) and late-type (down to redshifts ~1.0), respectively, with magnitudes F_613W_<=22.0. In addition, for magnitude range 22.0<F_613W_<=23.0, we classified other 10089 late-type galaxies with redshifts <=1.3. We show that the classified objects populate the expected regions in the colour-mass and colour-magnitude planes. The presented data set is especially attractive given the homogeneous multiwavelength coverage available in the ALHAMBRA fields, and is intended to be used in a variety of scientific applications. The low-contamination catalogue (<10 percent) is made publicly available with this paper.
- ID:
- ivo://CDS.VizieR/J/ApJ/823/160
- Title:
- ALMA 106GHz continuum observations in Chamaeleon I
- Short Name:
- J/ApJ/823/160
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an Atacama Large Millimeter/submillimeter Array (ALMA) 106 GHz (Band 3) continuum survey of the complete population of dense cores in the Chamaeleon I molecular cloud. We detect a total of 24 continuum sources in 19 different target fields. All previously known Class 0 and Class I protostars in Chamaeleon I are detected, whereas all of the 56 starless cores in our sample are undetected. We show that the Spitzer+Herschel census of protostars in Chamaeleon I is complete, with the rate at which protostellar cores have been misclassified as starless cores calculated as <1/56, or <2%. We use synthetic observations to show that starless cores collapsing following the turbulent fragmentation scenario are detectable by our ALMA observations when their central densities exceed ~10^8^/cm^3^, with the exact density dependent on the viewing geometry. Bonnor-Ebert spheres, on the other hand, remain undetected to central densities at least as high as 10^10^/cm^3^. Our starless core non-detections are used to infer that either the star-formation rate is declining in Chamaeleon I and most of the starless cores are not collapsing, matching the findings of previous studies, or that the evolution of starless cores are more accurately described by models that develop less substructure than predicted by the turbulent fragmentation scenario, such as Bonnor-Ebert spheres. We outline future work necessary to distinguish between these two possibilities.
