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441. Low-z intergalactic medium. III.
ID:
ivo://CDS.VizieR/J/ApJ/679/194
Title:
Low-z intergalactic medium. III.
Short Name:
J/ApJ/679/194
Date:
21 Oct 2021
Publisher:
CDS
Description:
We conduct an ultraviolet (HST and FUSE) spectroscopic survey of HI (Lyman lines) and seven metal ions (OVI, NV, CIV, CIII, SiIV, SiIII, FeIII) in the low-redshift IGM at z<0.4. We analyzed 650 Ly{alpha} absorbers over redshift path length {Delta}z=5.27, detecting numerous absorbers: 83 OVI systems, 39 CIII, 53 SiIII, 24 CIV, 24 NV, and so on. In the low-z IGM, we have accounted for ~40% of the baryons: 30% in the photoionized Ly{alpha} forest and 10% in the (T=10^5^-10^6^) WHIM traced by OVI. Statistical metallicities are consistent with the canonical value of 10% solar, with considerable scatter.
442. Luminosity and redshift of galaxies from WISE/SDSS
ID:
ivo://CDS.VizieR/J/ApJ/788/45
Title:
Luminosity and redshift of galaxies from WISE/SDSS
Short Name:
J/ApJ/788/45
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this work, we investigate the dependence of the covering factor (CF) of active galactic nuclei (AGNs) on the mid-infrared (MIR) luminosity and the redshift. We constructed 12 and 22 {mu}m luminosity functions (LFs) at 0.006<=z<=0.3 using Wide-field Infrared Survey Explorer (WISE) data. Combining the WISE catalog (Cat. II/311) with Sloan Digital Sky Survey (SDSS, Cat. II/294) spectroscopic data, we selected 223982 galaxies at 12 {mu}m and 25721 galaxies at 22 {mu}m for spectroscopic classification. We then identified 16355 AGNs at 12 {mu}m and 4683 AGNs at 22 {mu}m by their optical emission lines and cataloged classifications in the SDSS. Following that, we estimated the CF as the fraction of Type 2 AGN in all AGNs whose MIR emissions are dominated by the active nucleus (not their host galaxies) based on their MIR colors. We found that the CF decreased with increasing MIR luminosity, regardless of the choice of Type 2 AGN classification criteria, and the CF did not change significantly with redshift for z<=0.2. Furthermore, we carried out various tests to determine the influence of selection bias and confirmed that similar dependences exist, even when taking these uncertainties into account. The luminosity dependence of the CF can be explained by the receding torus model, but the "modified" receding torus model gives a slightly better fit, as suggested by Simpson.
443. Luminosity function of broad-line quasars
ID:
ivo://CDS.VizieR/J/ApJ/746/169
Title:
Luminosity function of broad-line quasars
Short Name:
J/ApJ/746/169
Date:
21 Oct 2021
Publisher:
CDS
Description:
We jointly constrain the luminosity function (LF) and black hole mass function (BHMF) of broad-line quasars with forward Bayesian modeling in the quasar mass-luminosity plane, based on a homogeneous sample of ~58000 Sloan Digital Sky Survey (SDSS) Data Release 7 quasars at z~0.3-5. We take into account the selection effect of the sample flux limit; more importantly, we deal with the statistical scatter between true BH masses and FWHM-based single-epoch virial mass estimates, as well as potential luminosity-dependent biases of these mass estimates. The LF is tightly constrained in the regime sampled by SDSS and makes reasonable predictions when extrapolated to ~3 mag fainter. Downsizing is seen in the model LF. On the other hand, we find it difficult to constrain the BHMF to within a factor of a few at z >~ 0.7 (with Mg II and C IV-based virial BH masses). This is mainly driven by the unknown luminosity-dependent bias of these mass estimators and its degeneracy with other model parameters, and secondly driven by the fact that SDSS quasars only sample the tip of the active BH population at high redshift. Nevertheless, the most likely models favor a positive luminosity-dependent bias for Mg II and possibly for C IV, such that at fixed true BH mass, objects with higher-than-average luminosities have overestimated FWHM-based virial masses. There is tentative evidence that downsizing also manifests itself in the active BHMF, and the BH mass density in broad-line quasars contributes an insignificant amount to the total BH mass density at all times. Within our model uncertainties, we do not find a strong BH mass dependence of the mean Eddington ratio, but there is evidence that the mean Eddington ratio (at fixed BH mass) increases with redshift.
444. Luminosity function of broad-line quasars. II.
ID:
ivo://CDS.VizieR/J/ApJ/764/45
Title:
Luminosity function of broad-line quasars. II.
Short Name:
J/ApJ/764/45
Date:
21 Oct 2021
Publisher:
CDS
Description:
We employ a flexible Bayesian technique to estimate the black hole (BH) mass and Eddington ratio functions for Type 1 (i.e., broad line) quasars from a uniformly selected data set of ~58000 quasars from the Sloan Digital Sky Survey (SDSS) DR7. We find that the SDSS becomes significantly incomplete at M_BH_<~3x10^8^M_{sun}_ or L/L_Edd_<~0.07, and that the number densities of Type 1 quasars continue to increase down to these limits. Both the mass and Eddington ratio functions show evidence of downsizing, with the most massive and highest Eddington ratio BHs experiencing Type 1 quasar phases first, although the Eddington ratio number densities are flat at z<2. We estimate the maximum Eddington ratio of Type 1 quasars in the observable universe to be L/L_Edd_~3. Consistent with our results in Shen & Kelly (Paper I, Cat. J/ApJ/746/169), we do not find statistical evidence for a so-called sub-Eddington boundary in the mass-luminosity plane of broad-line quasars, and demonstrate that such an apparent boundary in the observed distribution can be caused by selection effect and errors in virial BH mass estimates. Based on the typical Eddington ratio in a given mass bin, we estimate growth times for the BHs in Type 1 quasars and find that they are comparable to or longer than the age of the universe, implying an earlier phase of accelerated (i.e., with higher Eddington ratios) and possibly obscured growth. The large masses probed by our sample imply that most of our BHs reside in what are locally early-type galaxies, and we interpret our results within the context of models of self-regulated BH growth.
445. Luminosity function of X-ray-selected AGNs
ID:
ivo://CDS.VizieR/J/ApJ/802/89
Title:
Luminosity function of X-ray-selected AGNs
Short Name:
J/ApJ/802/89
Date:
21 Oct 2021
Publisher:
CDS
Description:
We aim to constrain the evolution of active galactic nuclei (AGNs) as a function of obscuration using an X-ray-selected sample of ~2000 AGNs from a multi-tiered survey including the CDFS, AEGIS-XD, COSMOS, and XMM-XXL fields. The spectra of individual X-ray sources are analyzed using a Bayesian methodology with a physically realistic model to infer the posterior distribution of the hydrogen column density and intrinsic X-ray luminosity. We develop a novel non-parametric method that allows us to robustly infer the distribution of the AGN population in X-ray luminosity, redshift, and obscuring column density, relying only on minimal smoothness assumptions. Our analysis properly incorporates uncertainties from low count spectra, photometric redshift measurements, association incompleteness, and the limited sample size. We find that obscured AGNs with N_H_>10^22^/cm2 account for 77_-5_^+4^% of the number density and luminosity density of the accretion supermassive black hole population with L_X_>10^43^erg/s, averaged over cosmic time. Compton-thick AGNs account for approximately half the number and luminosity density of the obscured population, and 38_-7_^+8^% of the total. We also find evidence that the evolution is obscuration dependent, with the strongest evolution around N_H_{approx}10^23^/cm2. We highlight this by measuring the obscured fraction in Compton-thin AGNs, which increases toward z~3, where it is 25% higher than the local value. In contrast, the fraction of Compton-thick AGNs is consistent with being constant at {approx}35%, independent of redshift and accretion luminosity. We discuss our findings in the context of existing models and conclude that the observed evolution is, to first order, a side effect of anti-hierarchical growth.
446. Luminous AGNs and early-type SDSS galaxies
ID:
ivo://CDS.VizieR/J/ApJ/804/34
Title:
Luminous AGNs and early-type SDSS galaxies
Short Name:
J/ApJ/804/34
Date:
21 Oct 2021
Publisher:
CDS
Description:
It is not yet clear what triggers the activity of active galactic nuclei (AGNs), but galaxy merging has been suspected to be one of the main mechanisms fueling the activity. Using deep optical images taken at various ground-based telescopes, we investigate the fraction of galaxy mergers in 39 luminous AGNs (M_R_<~-22.6mag) at z<=0.3 (a median redshift of 0.155), for which the host galaxies are generally considered as early-type galaxies. Through visual inspection of the images, we find that 17 of 39 AGN host galaxies (43.6%) show evidence for current or past mergers like tidal tails, shells, and disturbed morphology. In order to see if this fraction is abnormally high, we also examined the merging fraction of normal early-type galaxies in the Sloan Digital Sky Survey (SDSS) Stripe 82 data (a median redshift of 0.04), of which the surface-brightness limit is comparable to our imaging data. To correct for the effects related to the redshift difference of the two samples, we performed an image simulation by putting a bright point source as an artificial AGN in the images of SDSS early-type galaxies and placing them onto the redshifts of AGNs. The merging fraction in this realistic sample of simulated AGNs is only ~5-15% (1/4 to 1/8 of that of real AGNs). Our result strongly suggests that luminous AGN activity is associated with galaxy merging.
447. Luminous radio galaxies & type-2 quasars
ID:
ivo://CDS.VizieR/J/MNRAS/436/997
Title:
Luminous radio galaxies & type-2 quasars
Short Name:
J/MNRAS/436/997
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of a comparison between the environments of (1) a complete sample of 46 southern 2-Jy radio galaxies at intermediate redshifts (0.05<z<0.7), (2) a complete sample of 20 radio-quiet type-2 quasars (0.3<=z<=0.41), and (3) a control sample of 107 quiescent early-type galaxies at 0.2<=z<0.7 in the Extended Groth Strip. The environments have been quantified using angular clustering amplitudes (Bgq) derived from deep optical imaging data. Based on these comparisons, we discuss the role of the environment in the triggering of powerful radio-loud and radio-quiet quasars. When we compare the Bgq distributions of the type-2 quasars and quiescent early-type galaxies, we find no significant difference between them. This is consistent with the radio-quiet quasar phase being a short-lived but ubiquitous stage in the formation of all massive early-type galaxies. On the other hand, powerful radio galaxies are in denser environments than the quiescent population, and this difference between distributions of Bgq is significant at the 3{sigma} level. This result supports a physical origin of radio loudness, with high-density gas environments favouring the transformation of active galactic nucleus (AGN) power into radio luminosity, or alternatively, affecting the properties of the supermassive black holes themselves. Finally, focusing on the radio-loud sources only, we find that the clustering of weak-line radio galaxies (WLRGs) is higher than the strong-line radio galaxies (SLRGs), constituting a 3{sigma} result. 82 percent of the 2-Jy WLRGs are in clusters, according to our definition (Bgq>~400), versus only 31 percent of the SLRGs.
448. Ly{alpha} candidates from a MUSE survey of 6 AGNs
ID:
ivo://CDS.VizieR/J/ApJ/859/53
Title:
Ly{alpha} candidates from a MUSE survey of 6 AGNs
Short Name:
J/ApJ/859/53
Date:
21 Oct 2021
Publisher:
CDS
Description:
Recent theoretical models suggest that the early phase of galaxy formation could involve an epoch when galaxies are gas rich but inefficient at forming stars: a "dark galaxy" phase. Here, we report the results of our Multi-Unit Spectroscopic Explorer (MUSE) survey for dark galaxies fluorescently illuminated by quasars at z>3. Compared to previous studies which are based on deep narrowband (NB) imaging, our integral field survey provides a nearly uniform sensitivity coverage over a large volume in redshift space around the quasars as well as full spectral information at each location. Thanks to these unique features, we are able to build control samples at large redshift distances from the quasars using the same data taken under the same conditions. By comparing the rest-frame equivalent width (EW0) distributions of the Ly{alpha} sources detected in proximity to the quasars and in control samples, we detect a clear correlation between the locations of high-EW0 objects and the quasars. This correlation is not seen in other properties, such as Ly{alpha} luminosities or volume overdensities, suggesting the possible fluorescent nature of at least some of these objects. Among these, we find six sources without continuum counterparts and EW0 limits larger than 240{AA} that are the best candidates for dark galaxies in our survey at z>3.5. The volume densities and properties, including inferred gas masses and star formation efficiencies, of these dark galaxy candidates are similar to those of previously detected candidates at z~2.4 in NB surveys. Moreover, if the most distant of these are fluorescently illuminated by the quasar, our results also provide a lower limit of t=60Myr on the quasar lifetime.
449. Ly{alpha}-emitting galaxies at 0.2<z<0.35
ID:
ivo://CDS.VizieR/J/ApJ/680/1072
Title:
Ly{alpha}-emitting galaxies at 0.2<z<0.35
Short Name:
J/ApJ/680/1072
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have used the GALEX (Galaxy Evolution Explorer) spectroscopic survey mode, with a resolution of ~8{AA} in the far-ultraviolet (FUV; 1350-1750{AA}) and ~20{AA} in the near-ultraviolet (NUV; 1950-2750{AA}) for a systematic search of Ly{alpha}-emitting galaxies at low redshift. Our aim is to fill a gap between high-redshift surveys and a small set of objects studied in detail in the nearby universe. A blind search of 7018 spectra extracted in five deep exposures (5.65deg^2^) has resulted in 96 Ly{alpha}-emitting galaxy candidates in the FUV domain after accounting for broad-line AGNs.
450. Lyman Continuum in 111 GOODS and ERS galaxies
ID:
ivo://CDS.VizieR/J/ApJ/897/41
Title:
Lyman Continuum in 111 GOODS and ERS galaxies
Short Name:
J/ApJ/897/41
Date:
11 Mar 2022
Publisher:
CDS
Description:
We present our analysis of the Lyman continuum (LyC) emission and escape fraction of 111 spectroscopically verified galaxies with and without active galactic nuclei (AGN) from 2.26<z<4.3. We extended our ERS sample from Smith et al. with 64 galaxies in the GOODS North and South fields using WFC3/UVIS F225W, F275W, and F336W mosaics we independently drizzled using the HDUV, CANDELS, and UVUDF data. Among the 17 AGN from the 111 galaxies, one provided a LyC detection in F275W at m_AB_=23.19mag (signal-to-noise ratio, S/N~133) and GALEX NUV at m_AB_=23.77mag (S/N~13). We simultaneously fit SDSS and Chandra spectra of this AGN to an accretion disk and Comptonization model, and find f_esc_ values of f_esc_^F275W^~28_-4_^+20^% and f_esc_^NUV^~30_-5_^+22^% . For the remaining 110 galaxies, we stack image cutouts that capture their LyC emission using the F225W, F275W, and F336W data of the GOODS and ERS samples, and both combined, as well as subsamples of galaxies with and without AGN, and all galaxies. We find the stack of 17 AGN dominate the LyC production from <z>~2.3-4.3 by a factor of ~10 compared to all 94 galaxies without AGN. While the IGM of the early universe may have been reionized mostly by massive stars, there is evidence that a significant portion of the ionizing energy came from AGN.