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621. Properties of BQS objects in the SDSS DR3 area
ID:
ivo://CDS.VizieR/J/AJ/130/873
Title:
Properties of BQS objects in the SDSS DR3 area
Short Name:
J/AJ/130/873
Date:
21 Oct 2021
Publisher:
CDS
Description:
We investigate the extent to which the Palomar-Green (PG) Bright Quasar Survey (BQS) is complete and representative of the general quasar population by comparing it with imaging and spectroscopy from the Sloan Digital Sky Survey (SDSS).
622. Properties of low z QSO absorption systems
ID:
ivo://CDS.VizieR/J/ApJS/122/355
Title:
Properties of low z QSO absorption systems
Short Name:
J/ApJS/122/355
Date:
21 Oct 2021
Publisher:
CDS
Description:
(Partial): We examine the clustering properties of low-redshift Ly{alpha} and heavy-element QSO absorption line systems seen in the spectra of 13 QSOs at the Galactic poles. This is the densest sample of ~1 degree separated QSOs observed spectroscopically with the Hubble Space Telescope to date. At the median redshift of the Ly{alpha} sample (z{=~}0.7), the QSO lines of sight are separated on transverse scales from about 15 to 200h^-1^Mpc (q_0_=0.5, H=100h.km/s/Mpc), allowing the three-dimensional clustering of the absorbers to be examined on those scales. The Galactic poles are also regions where relatively deep and wide-field galaxy redshift surveys have taken place, so the distributions of galaxies and Ly{alpha} systems can be compared within the same volume of space. There are 545 total absorption lines detected in the complete sample from 13 QSOs. We identify 307 Ly{alpha} systems, of which 18 contain heavy-element lines. We confirm the relatively slow redshift number density evolution for Ly systems at z{<=}1. There are also five likely C IV doublets in our sample, for which the Ly{alpha} line is not accessible.
623. Properties of radio-loud BAL quasars
ID:
ivo://CDS.VizieR/J/MNRAS/427/1135
Title:
Properties of radio-loud BAL quasars
Short Name:
J/MNRAS/427/1135
Date:
21 Oct 2021
Publisher:
CDS
Description:
We recently presented radio observations of a large sample of radio-loud broad absorption line (BAL) quasars from the Sloan Digital Sky Survey (SDSS) and Faint Images of the Radio Sky at Twenty-cm surveys, as well as a well matched sample of unabsorbed quasars, primarily to measure their radio spectral indices and estimate ensemble orientations. Here, we analyse the SDSS spectra of these samples and compare the rest-frame ultraviolet properties of radio-loud BAL and non-BAL quasars. Ultraviolet properties include the continuum shape, emission-line measurements of CIV, AlIII, CIII], FeII and MgII, and BAL properties including the balnicity index, absorption index and minimum and maximum outflow velocities. We find that radio-loud BAL quasars have similar ultraviolet properties compared to radio-loud non-BAL sources, though they do appear to have redder continua and stronger FeII emission, which is consistent with what is found for radio-quiet BAL sources. No correlations exist between outflow properties and orientation (radio spectral index), suggesting that BAL winds along any line of sight are driven by the same mechanisms. There are also few correlations between spectral index and other properties. We conclude that BAL outflows occur along all lines of sight with similar strengths and velocities.
624. Properties of SDSS QSOs in the ChaMP
ID:
ivo://CDS.VizieR/J/ApJ/690/644
Title:
Properties of SDSS QSOs in the ChaMP
Short Name:
J/ApJ/690/644
Date:
21 Oct 2021
Publisher:
CDS
Description:
We study the spectral energy distributions and evolution of a large sample of optically selected quasars from the Sloan Digital Sky Survey that were observed in 323 Chandra images analyzed by the Chandra Multiwavelength Project. Our highest-confidence matched sample includes 1135 X-ray detected quasars in the redshift range 0.2<z<5.4, representing some 36Msec of effective exposure. We provide catalogs of QSO properties, and describe our novel method of calculating X-ray flux upper limits and effective sky coverage. Spectroscopic redshifts are available for about 1/3 of the detected sample; elsewhere, redshifts are estimated photometrically. We detect 56 QSOs with redshift z>3, substantially expanding the known sample. We find no evidence for evolution out to z~5 for either the X-ray photon index {Gamma} or for the ratio of optical/UV to X-ray flux {alpha}_ox_.
625. Properties of the highly ionized gas of quasars
ID:
ivo://CDS.VizieR/J/ApJ/788/119
Title:
Properties of the highly ionized gas of quasars
Short Name:
J/ApJ/788/119
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the first results from our NASA Keck Observatory Database of Ionized Absorbers toward Quasars (KODIAQ) survey which aims to characterize the properties of the highly ionized gas of galaxies and their circumgalactic medium (CGM) at 2<z<4. We select absorbers optically thick at the Lyman limit ({tau}_LL_>1, logN_HI_>17.3}) as probes of these galaxies and their CGM where both transitions of the O VI doublet have little contamination from the Ly{alpha}, {beta} forests. We found 20 absorbers that satisfy these rules: 7 Lyman limit systems (LLSs), 8 super-LLSs (SLLSs) and 5 damped Ly{alpha} (DLAs). The O VI detection rate is 100% for the DLAs, 71% for the LLSs, and 63% for the SLLSs. When O VI is detected, log(N_O VI_)=14.9+/-0.3, an average O VI column density substantially larger and with a smaller dispersion than found in blind O VI surveys at similar redshifts. Strong O VI absorption is therefore nearly ubiquitous in the CGM of z~2-3 galaxies. The total velocity widths of the O VI profiles are also large (200<={Delta}_{upsilon}_O VI_<=400 km/s). These properties are quite similar to those seen for O VI in low-z star-forming galaxies, and therefore we hypothesize that these strong CGM O VI absorbers (with {tau}_LL_>1) at 2<z<~3.5 also probe outflows of star-forming galaxies. The LLSs and SLLSs with no O VI absorption have properties consistent with those seen in cosmological simulations tracing cold streams feeding galaxies. When the highly ionized (Si IV and O VI) gas is taken into account, we determine that the {tau}_LL_>1 absorbers could contain as much as 3%-14% of the cosmic baryon budget at z~2-3, only second to the Ly{alpha} forest. We conservatively show that 5%-20% of the metals ever produced at z~2-3 are in form of highly ionized metals ejected in the CGM of galaxies.
626. Properties of weak emission-line QSOs (WLQ)
ID:
ivo://CDS.VizieR/J/ApJ/696/580
Title:
Properties of weak emission-line QSOs (WLQ)
Short Name:
J/ApJ/696/580
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present Chandra observations of nine high-redshift quasars (z=2.7-5.9) discovered by the Sloan Digital Sky Survey with weak or undetectable high-ionization emission lines in their UV spectra (WLQs). Adding archival X-ray observations of six additional sources of this class has enabled us to place the strongest constraints yet on the X-ray properties of this remarkable class of active galactic nuclei (AGNs). Although our data cannot rule out the possibility that the emission lines are overwhelmed by a relativistically boosted continuum, as manifested by BL Lac objects, we find that WLQs are considerably weaker in the X-ray and radio bands than the majority of BL Lacs found at much lower redshifts. If WLQs are high-redshift BL Lacs, then it is difficult to explain the lack of a large parent population of X-ray and radio bright weak-lined sources at high redshift. We also consider the possibility that WLQs are quasars with extreme properties, and in particular that the emission lines are suppressed by high accretion rates. Using joint spectral fitting of the X-ray spectra of 11 WLQs, we find that the mean photon index in the hard X-ray band is consistent with those observed in typical radio-quiet AGNs with no hint of an unusually steep hard-X-ray spectrum. This result poses a challenge to the hypothesis that WLQs have extremely high accretion rates, and we discuss additional observations required to test this idea.
627. Proximate damped Ly{alpha} systems in SDSS-DR5
ID:
ivo://CDS.VizieR/J/ApJ/675/1002
Title:
Proximate damped Ly{alpha} systems in SDSS-DR5
Short Name:
J/ApJ/675/1002
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using the Sloan Digital Sky Survey Data Release 5 (SDSS-DR5), we survey proximate damped Ly{alpha} systems (PDLAs): absorption-line systems with HI column density N_H_>=2x10^20^cm^-2^ at velocity separation {delta}v<2999km/s from their background quasar. Many of these absorbers may be physically associated with their background quasars, and their statistics allow us to study quasar environments out to z~5. However, the large ionizing flux emitted by a quasar can ionize the neutral gas in a nearby galaxy, possibly giving rise to a "proximity effect", analogous to the similar effect observed in the Ly{alpha} forest. From a sample of 108 PDLAs, we measure the HI frequency distribution f(N_H_,X) incidence, and gas mass density of the PDLAs near luminous quasars over the redshift interval z=2.2-5. The incidence and mass density of PDLAs at z~3 is approximately twice that of intervening DLAs, while at z<2.5 and >3.5 the f(N_H_X) distribution is enhanced but statistically consistent with the intervening population. We interpret the observed enhancement of PDLAs around quasars in terms of quasar-galaxy clustering and compare the strength of the clustering signal to the expectation from independent measures of the respective clustering strengths of DLAs and quasars, as well as a complementary analysis of the clustering of absorbers around quasars in the transverse direction. We find that there are a factor of 5-10 fewer PDLAs around quasars than expected and interpret this result as evidence for the hypothesis that the ionizing flux from the quasars photoevaporates HI in nearby DLA galaxies, thus reducing their cross section for DLA absorption. This constitutes the first detection of a "proximity effect" for DLAs.
628. PS1 photometry of 2863 ICRF3 quasars
ID:
ivo://CDS.VizieR/J/AJ/162/21
Title:
PS1 photometry of 2863 ICRF3 quasars
Short Name:
J/AJ/162/21
Date:
14 Mar 2022 06:53:33
Publisher:
CDS
Description:
We make use of individual (epoch) detection data from the Pan-STARRS "3{pi}" survey for 2863 optical ICRF3 counterparts in the five wavelength bands g, r, i, z, and y, published as part of the Data Release 2. A dedicated method based on the Functional Principal Component Analysis is developed for these sparse and irregularly sampled data. With certain regularization and normalization constraints, it allows us to obtain uniform and compatible estimates of the variability amplitudes and average magnitudes between the passbands and objects. We find that the starting assumption of affinity of the light curves for a given object at different wavelengths is violated for several percent of the sample. The distributions of rms variability amplitudes are strongly skewed toward small values, peaking at ~0.1mag with tails stretching to 2mag. Statistically, the lowest variability is found for the r band and the largest for the reddest y band. A small "brighter-redder" effect is present, with amplitudes in y greater than amplitudes in g in 57% of the sample. The variability versus redshift dependence shows a strong decline with z toward redshift 3, which we interpret as the time dilation of the dominant time frequencies. The colors of radio-loud ICRF3 quasars are correlated with redshift in a complicated, wavy pattern governed by the emergence of brightest emission lines within the five passbands.
629. PS1 z>5.6 quasars follow-up
ID:
ivo://CDS.VizieR/J/ApJS/227/11
Title:
PS1 z>5.6 quasars follow-up
Short Name:
J/ApJS/227/11
Date:
21 Oct 2021
Publisher:
CDS
Description:
Luminous quasars at z>5.6 can be studied in detail with the current generation of telescopes and provide us with unique information on the first gigayear of the universe. Thus far, these studies have been statistically limited by the number of quasars known at these redshifts. Such quasars are rare, and therefore, wide-field surveys are required to identify them, and multiwavelength data are required to separate them efficiently from their main contaminants, the far more numerous cool dwarfs. In this paper, we update and extend the selection for the z~6 quasars presented in Banados+ (2014AJ....148...14B) using the Pan-STARRS1 (PS1) survey. We present the PS1 distant quasar sample, which currently consists of 124 quasars in the redshift range 5.6<~z<~6.7 that satisfy our selection criteria. Of these quasars, 77 have been discovered with PS1, and 63 of them are newly identified in this paper. We present the composite spectra of the PS1 distant quasar sample. This sample spans a factor of ~20 in luminosity and shows a variety of emission line properties. The number of quasars at z>5.6 presented in this work almost doubles the previously known quasars at these redshifts, marking a transition phase from studies of individual sources to statistical studies of the high-redshift quasar population, which was impossible with earlier, smaller samples.
630. QJ0643-5041 UVES spectra
ID:
ivo://CDS.VizieR/J/A+A/562/A88
Title:
QJ0643-5041 UVES spectra
Short Name:
J/A+A/562/A88
Date:
21 Oct 2021
Publisher:
CDS
Description:
Molecular hydrogen in the interstellar medium (ISM) of high-redshift galaxies can be detected directly from its UV absorptions imprinted in the spectrum of background quasars. Associated absorptions from HI and metals allow for the study of the chemical enrichment of the gas, while the analysis of excited species and molecules make it possible to infer the physical state of the ISM gas. In addition, given the numerous H_2_ lines usually detected, these absorption systems are unique tools to constrain the cosmological variation of the proton-to-electron mass ratio, {mu}. We intend to study the chemical and physical state of the gas in the H_2_-bearing cloud at z_abs_=2.658601 towards the quasar QJ0643-5041 (z_em_=3.09) and to derive a useful constraint on the variation of {mu}. We use high signal-to-noise ratio, high-resolution VLT-UVES data of QJ0643-5041 amounting to a total of more than 23 hours exposure time and fit the HI, metals, and H_2_ absorption features with multiple-component Voigt profiles. We study the relative populations of H_2_ rotational levels and the fine-structure excitation of neutral carbon to determine the physical conditions in the H_2_-bearing cloud.