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- ID:
- ivo://CDS.VizieR/J/ApJ/887/5
- Title:
- COS CGM compendium (CCC). III. z<=1 Ly{alpha} syst.
- Short Name:
- J/ApJ/887/5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We characterize the metallicities and physical properties of cool, photoionized gas in a sample of 152 z<=1 strong Ly{alpha} forest systems (SLFSs, absorbers with 15<logN_HI_<16.2). The sample is drawn from our Cosmic Origins Spectrograph (COS) circumgalactic medium compendium (CCC), an ultraviolet survey of HI-selected circumgalactic gas around z<=1 galaxies that targets 261 absorbers with 15<logN_HI_<19. We show that the metallicity probability distribution function of the SLFSs at z<=1 is unimodal, skewed to low metallicities with a mean and median of [X/H]=-1.47 and -1.18dex. Very metal-poor gas with [X/H]{<}-1.4 represents about half of the population of absorbers with 15<logN_HI_<=18, while it is rare at higher N_HI_. Thus, there are important reservoirs of primitive (though not pristine) diffuse ionized gas around z<=1 galaxies. The photoionized gas around z<=1 galaxies is highly inhomogeneous based on the wide range of metallicities observed (-3<=[X/H]<=+0.4) and the fact that there are large metallicity variations (factors of 2 to 25) for most of the closely spaced absorbers ({Delta}v<=300km/s) along the same sightlines. These absorbers show a complex evolution with redshift and HI column density, and we identify subtle cosmic evolution effects that affect the interpretation of metallicity distributions and comparison with other absorber samples. We discuss the physical conditions and cosmic baryon and metal budgets of the CCC absorbers. Finally, we compare the CCC results to recent cosmological zoom simulations and explore the origins of the 15<logN_HI_<19 absorbers within the Evolution and Assembly of GaLaxies and their Environments (EAGLE) high-resolution simulations.
- ID:
- ivo://CDS.VizieR/J/ApJ/669/821
- Title:
- CO Tully-Fisher relation for host galaxies of QSOs
- Short Name:
- J/ApJ/669/821
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The integrated line width derived from CO spectroscopy provides a powerful tool to study the internal kinematics of extragalactic objects, including quasars at high redshift, provided that the observed line width can be properly translated to more conventionally used kinematical parameters of galaxies. We show, through the construction of a Ks-band CO Tully-Fisher relation for nearby galaxies spanning a wide range in infrared luminosity, that the CO line width measured at 20% of the peak intensity, when corrected for inclination and other effects, successfully recovers the maximum rotation velocity of the disk. The line width at 50% of the peak intensity performs much more poorly, in large part because CO lines have a wide range of profiles, which are shown to vary systematically with infrared luminosity. We present a practical prescription for converting observed CO line widths into the stellar velocity dispersion of the bulge ({sigma}*) and then apply it to a sample of low-redshift (z<~0.2) and high-redshift (1.4<~z<~6.4) quasars to study their host galaxies.
- ID:
- ivo://CDS.VizieR/J/MNRAS/430/3445
- Title:
- Covering factor of warm dust in quasars
- Short Name:
- J/MNRAS/430/3445
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- By combining newly obtained infrared photometric data from the All-Sky Data Release of the Wide-field Infrared Survey Explorer with spectroscopic data from the Seventh Data Release of the Sloan Digital Sky Survey, we study the covering factor of warm dust (CFWD) for a large quasar sample, as well as the relations between CFWD and other physical parameters of quasars. We find a strong correlation between the flux ratio in the mid-infrared to near-ultraviolet and the slope of the near-ultraviolet spectra, which is interpreted as a dust extinction effect. After correcting for dust extinction utilizing the above correlation, we examine the relations between CFWD and active galactic nucleus properties: bolometric luminosity (L_bol_), black hole mass (M_BH_) and Eddington ratio (L/L_Edd_). We confirm the anticorrelation between CFWD and L_bol_. Further, we find that CFWD is anticorrelated with M_BH_ but is independent of L/L_Edd_. Radio-loud quasars are found to follow the same correlations as radio-quiet quasars. Monte Carlo simulations show that the anisotropy of the UV-optical continuum of the accretion disc can have a significant effect, but is not likely to dominate the CFWD-L_bol_ correlation.
- ID:
- ivo://CDS.VizieR/J/MNRAS/453/1562
- Title:
- CRTS close supermassive black hole binaries
- Short Name:
- J/MNRAS/453/1562
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Hierarchical assembly models predict a population of supermassive black hole (SMBH) binaries. These are not resolvable by direct imaging but may be detectable via periodic variability (or nanohertz frequency gravitational waves). Following our detection of a 5.2-year periodic signal in the quasar PG 1302-102, we present a novel analysis of the optical variability of 243 500 known spectroscopically confirmed quasars using data from the Catalina Real-time Transient Survey (CRTS) to look for close (<0.1pc) SMBH systems. Looking for a strong Keplerian periodic signal with at least 1.5 cycles over a baseline of nine years, we find a sample of 111 candidate objects. This is in conservative agreement with theoretical predictions from models of binary SMBH populations. Simulated data sets, assuming stochastic variability, also produce no equivalent candidates implying a low likelihood of spurious detections. The periodicity seen is likely attributable to either jet precession, warped accretion discs or periodic accretion associated with a close SMBH binary system. We also consider how other SMBH binary candidates in the literature appear in CRTS data and show that none of these are equivalent to the identified objects. Finally, the distribution of objects found is consistent with that expected from a gravitational-wave-driven population. This implies that circumbinary gas is present at small orbital radii and is being perturbed by the black holes. None of the sources is expected to merge within at least the next century. This study opens a new unique window to study a population of close SMBH binaries that must exist according to our current understanding of galaxy and SMBH evolution.
- ID:
- ivo://CDS.VizieR/J/ApJ/636/610
- Title:
- Damped Ly{alpha} systems at z<1.65
- Short Name:
- J/ApJ/636/610
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of our Hubble Space Telescope Cycle 11 survey for low-redshift (z<1.65) damped Ly{alpha} (DLA) systems in the UV spectra of quasars selected from the Sloan Digital Sky Survey (SDSS) Early Data Release (Cat. <J/AJ/123/567>). These quasars have strong intervening MgII-FeII systems that are known signatures of high column density neutral gas. In total, including our previous surveys, UV observations of Ly{alpha} absorption in 197 MgII systems with z<1.65 and rest equivalent width (REW) W_0_^{lambda}2796^>=0.3{AA} have now been obtained.
- ID:
- ivo://CDS.VizieR/J/A+A/508/133
- Title:
- Damped Lyman{alpha} absorbers in z>4 QSOs
- Short Name:
- J/A+A/508/133
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a survey of damped (DLA, logN(HI)>20.3) and sub-damped Lyman-{alpha} systems (19.5<logN(HI)<20.3) at z>2.55 along the lines-of-sight to 77 quasars with emission redshifts in the range 4<z_em_<6.3. Intermediate resolution (R~4300) spectra were obtained with the Echellette Spectrograph and Imager (ESI) mounted on the Keck telescope. A total of 100 systems with logN(HI)>19.5 were detected of which 40 systems are damped Lyman-{alpha} systems for an absorption length of {Delta}X= 378. About half of the lines of sight of this homogeneous survey have never been investigated for DLAs.
- ID:
- ivo://CDS.VizieR/J/other/PASA/19.455
- Title:
- Damped Lyman alpha absorption of QSOs
- Short Name:
- J/other/PASA/19.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalogue of the 322 damped Lyman alpha absorbers taken from the literature. All damped Lyman alpha absorbers are included, with no selection on redshift or quasar magnitude. Of these, 123 are candidates and await confirmation using high resolution spectroscopy. For all 322 objects we catalogue the radio properties of the background quasars, when known. Around 60 quasars have radio flux densities above 0.1Jy and approximately half of these have optical magnitudes brighter than V=18. This compilation should prove useful in several areas of extragalactic/cosmological research.
- ID:
- ivo://CDS.VizieR/J/MNRAS/392/998
- Title:
- Damped Lyman{alpha} systems
- Short Name:
- J/MNRAS/392/998
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using a sample of 21 damped Lyman alpha systems (DLAs) and 35 sub-DLAs, we evaluate the D-index=[EW({AA})/{Delta}v(km/s)]x1000 from high-resolution spectra of the MgII {lambda}2796 profile. This sample represents an increase in the sub-DLA statistics by a factor of 4 over the original D-index sample. We investigate various techniques to define the velocity spread ({Delta}v) of the MgII line to determine an optimal D-index for the identification of DLAs. The success rate of DLA identification is 50-55 per cent, depending on the velocity limits used, improving by a few per cent when the column density of FeII is included in the D-index calculation. We recommend the set of parameters that are judged to be most robust, have a combination of high DLA identification rate (57 per cent) and low DLA miss rate (6 per cent) and most cleanly separate the DLAs and sub-DLAs (Kolmogorov-Smirnov probability 0.5 per cent). These statistics demonstrate that the D-index is the most efficient technique for selecting low-redshift DLA candidates.
- ID:
- ivo://CDS.VizieR/J/MNRAS/471/3428
- Title:
- Damped Lyman Alpha systems equivalent width
- Short Name:
- J/MNRAS/471/3428
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We derive the statistical properties of neutral gas at redshifts 0.11<z<1.65 from ultraviolet (UV) measurements of quasar Ly{alpha} absorption lines corresponding to 369 MgII systems with W{lambda}2796_0_>=0.3{AA}. In addition to the 41 damped Lyman alpha (DLA) systems presented in Rao et al. (2006ApJ...636..610R, Cat. J/ApJ/636/610), the current DLA sample includes 29 newly discovered DLAs. Formally, this DLA sample includes 70 systems with N_HI_>=2*10^20^atoms/cm^2^. We find that the incidence of DLAs, or the product of their gas cross-section and their comoving number density, can be described by n_DLA_(z)=(0.027+/-0.007)(1+z)^(1.682+/-0.200)^ over the redshift range of 0<z<5. The cosmic mass density of neutral gas can be described by {Omega}_DLA_(z)=(4.77+/-1.60)x10^-4^(1+z)^(0.64+/-0.27)^. The low-redshift column density distribution function is well fitted by a power law of the form f(N)~N^{beta}^ with {beta}=-1.46+/-0.20. It is consistent with the high redshift as well as z=0 estimates at the high-column density end but lies between them at the low-column density end. We discuss possible N_HI_ and metallicity bias in Mg II-selected DLA samples and show that such biases do not exist in the current data at z<1.65. Thus, at least at z<1.65, DLAs found through MgII selection statistically represent the true population of DLAs. However, we caution that studies of DLA metallicities should take into account the relative incidence of DLAs with respect to W_0_{lambda}2796^ (or gas velocity spread) in order to
