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831. SDSS quasar lens search
ID:
ivo://CDS.VizieR/J/AJ/132/999
Title:
SDSS quasar lens search
Short Name:
J/AJ/132/999
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present an algorithm for selecting a uniform sample of gravitationally lensed quasar candidates from low-redshift (0.6<z<2.2) quasars brighter than i=19.1 that have been spectroscopically identified in the Sloan Digital Sky Survey (SDSS). Our algorithm uses morphological and color selections that are intended to identify small- and large-separation lenses, respectively. Our selection algorithm only relies on parameters that the SDSS standard image processing pipeline generates, allowing easy and fast selection of lens candidates. The algorithm has been tested against simulated SDSS images, which adopt distributions of field and quasar parameters taken from the real SDSS data as input. Furthermore, we take differential reddening into account. We find that our selection algorithm is almost complete down to separations of 1" and flux ratios of 10^-0.5^.
832. SDSS quasar lens search. II.
ID:
ivo://CDS.VizieR/J/AJ/135/496
Title:
SDSS quasar lens search. II.
Short Name:
J/AJ/135/496
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the first results of our systematic search for strongly lensed quasars using the spectroscopically confirmed quasars in the Sloan Digital Sky Survey (SDSS). Among 46420 quasars from the SDSS Data Release 3 (~4188deg^2^), we select a subsample of 22683 quasars that are located at redshifts between 0.6 and 2.2 and are brighter than the Galactic extinction-corrected i-band magnitude of 19.1. We identify 220 lens candidates from the quasar subsample, for which we conduct extensive and systematic follow-up observations in optical and near-infrared wavebands, in order to construct a complete lensed quasar sample at image separations between 1" and 20" and flux ratios of faint to bright lensed images larger than 10^-0.5^. We construct a statistical sample of 11 lensed quasars. Ten of these are galaxy-scale lenses with small image separations (~1"-2") and one is a large separation (15") system which is produced by a massive cluster of galaxies, representing the first statistical sample of lensed quasars including both galaxy- and cluster-scale lenses. The Data Release 3 spectroscopic quasars contain an additional 11 lensed quasars outside the statistical sample.
833. SDSS Quasar Lens Search. IV.
ID:
ivo://CDS.VizieR/J/AJ/140/403
Title:
SDSS Quasar Lens Search. IV.
Short Name:
J/AJ/140/403
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the second report of our systematic search for strongly lensed quasars from the data of the Sloan Digital Sky Survey (SDSS). From extensive follow-up observations of 136 candidate objects, we find 36 lenses in the full sample of 77,429 spectroscopically confirmed quasars in the SDSS Data Release 5.
834. SDSS Quasar Lens Search. V. Final catalog
ID:
ivo://CDS.VizieR/J/AJ/143/119
Title:
SDSS Quasar Lens Search. V. Final catalog
Short Name:
J/AJ/143/119
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the final statistical sample of lensed quasars from the Sloan Digital Sky Survey (SDSS) Quasar Lens Search (SQLS). The well-defined statistical lens sample consists of 26 lensed quasars brighter than i=19.1 and in the redshift range of 0.6<z<2.2 selected from 50826 spectroscopically confirmed quasars in the SDSS Data Release 7 (DR7), where we restrict the image separation range to 1"<{theta}<20" and the i-band magnitude differences in two images to be smaller than 1.25mag. The SDSS-DR7 quasar catalog also contains 36 additional lenses identified with various techniques. In addition to these lensed quasars, we have identified 81 pairs of quasars from follow-up spectroscopy, 26 of which are physically associated binary quasars. The statistical lens sample covers a wide range of image separations, redshifts, and magnitudes, and therefore is suitable for systematic studies of cosmological parameters and surveys of the structure and evolution of galaxies and quasars.
835. SDSS quasars balmer emission lines
ID:
ivo://CDS.VizieR/J/ApJ/789/140
Title:
SDSS quasars balmer emission lines
Short Name:
J/ApJ/789/140
Date:
21 Oct 2021
Publisher:
CDS
Description:
A small fraction of quasars have long been known to show bulk velocity offsets (of a few hundred to thousands of km/s) in the broad Balmer lines with respect to the systemic redshift of the host galaxy. Models to explain these offsets usually invoke broad-line region gas kinematics/asymmetry around single black holes (BHs), orbital motion of massive (~sub-parsec (sub-pc)) binary black holes (BBHs), or recoil BHs, but single-epoch spectra are unable to distinguish between these scenarios. The line-of-sight (LOS) radial velocity (RV) shifts from long-term spectroscopic monitoring can be used to test the BBH hypothesis. We have selected a sample of 399 quasars with kinematically offset broad H{beta} lines from the Sloan Digital Sky Survey (SDSS) Seventh Data Release quasar catalog, and have conducted second-epoch optical spectroscopy for 50 of them. Combined with the existing SDSS spectra, the new observations enable us to constrain the LOS RV shifts of broad H{beta} lines with a rest-frame baseline of a few years to nearly a decade. While previous work focused on objects with extreme velocity offset (>10^3^ km/s), we explore the parameter space with smaller (a few hundred km/s) yet significant offsets (99.7% confidence). Using cross-correlation analysis, we detect significant (99% confidence) radial accelerations in the broad H{beta} lines in 24 of the 50 objects, of ~10-200 km/s/yr with a median measurement uncertainty of ~10 km/s/yr, implying a high fraction of variability of the broad-line velocity on multi-year timescales. We suggest that 9 of the 24 detections are sub-pc BBH candidates, which show consistent velocity shifts independently measured from a second broad line (either H{alpha} or Mg II) without significant changes in the broad-line profiles. Combining the results on the general quasar population studied in Paper I (Shen et al. 2013ApJ...775...49S), we find a tentative anti-correlation between the velocity offset in the first-epoch spectrum and the average acceleration between two epochs, which could be explained by orbital phase modulation when the time separation between two epochs is a non-negligible fraction of the orbital period of the motion causing the line displacement. We discuss the implications of our results for the identification of sub-pc BBH candidates in offset-line quasars and for the constraints on their frequency and orbital parameters.
836. SDSS quasars in SWIRE ELAIS N1 field
ID:
ivo://CDS.VizieR/J/AJ/129/1198
Title:
SDSS quasars in SWIRE ELAIS N1 field
Short Name:
J/AJ/129/1198
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a mid-infrared (MIR) analysis of 35 quasars with spectroscopic redshifts selected from the Spitzer Wide-Area Infrared Extragalactic Survey (SWIRE). We discuss their optical and MIR colors and show that these quasars occupy well-defined regions in MIR color-color space. We examine the issue of type 1 active galactic nuclei candidate selection in detail and propose new selection methods based on MIR colors. The available multiband data allow us to construct two new, well-sampled quasar templates, covering wavelengths from the ultraviolet to the MIR.
837. SDSS quasars in the COSMOS field
ID:
ivo://CDS.VizieR/J/ApJ/644/100
Title:
SDSS quasars in the COSMOS field
Short Name:
J/ApJ/644/100
Date:
21 Oct 2021
Publisher:
CDS
Description:
We obtained medium-resolution spectra of 336 quasar candidates in the COSMOS HST Treasury field using the MMT 6.5m telescope and the Hectospec multiobject spectrograph. Candidates were drawn from the Sloan Digital Sky Survey (SDSS) DR1 catalog using quasar flags set by the SDSS multicolor quasar target selection algorithm. In this paper we present our discovery spectra from 1.39deg^2^ (69.5% of the COSMOS field) and a discussion of the selection method and yields. We confirmed 95 quasars, including at least two BAL quasars; 80 of these are new quasars that do not appear in previous quasar confirmation follow-up studies. The candidates additionally included 184 compact emission-line galaxies, a third of which are likely type 2 AGNs, and 12 stars. The quasars span a range in magnitude of 18.3<g<22.5 and a range in redshift of 0.2<z<2.3. Our results are consistent with a lower limit quasar surface density from SDSS color selection of 102deg^-2^ down to g=22.5 over the entire COSMOS field. This work is the first step toward the eventual goal of setting up a grid of quasar absorption line probes of the 2deg^2^ field and of conducting a complete census of supermassive black holes in this well-studied survey region. The total quasar count at the conclusion of this study is 139, making COSMOS one of the most densely sampled regions of sky where a grid of quasar sight lines can be used to probe the intervening volume.
838. SDSS quasars with PV broad absorption
ID:
ivo://CDS.VizieR/J/MNRAS/469/323
Title:
SDSS quasars with PV broad absorption
Short Name:
J/MNRAS/469/323
Date:
21 Oct 2021
Publisher:
CDS
Description:
Broad absorption lines (BALs) found in a significant fraction of quasar spectra identify high-velocity outflows that might be present in all quasars and could be a major factor in feedback to galaxy evolution. Understanding the nature of these flows requires further constraints on their physical properties, including their column densities, for which well-studied BALs, such as CIV {lambda}{lambda}1548,1551, typically provide only a lower limit because of saturation effects. Low-abundance lines, such as PV {lambda}{lambda}1118,1128, indicate large column densities, implying that outflows more powerful than measurements of CIV alone would indicate. We search through a sample of 2694 BAL quasars from the Sloan Digital Sky Survey III/Baryon Oscillation Spectroscopic Survey data release 9 quasar catalogue for such absorption, and we identify 81 'definite' and 86 'probable' detections of PV broad absorption, yielding a firm lower limit of 3.0-6.2 per cent for the incidence of such absorption among BAL quasars. The PV-detected quasars tend to have stronger CIV and SiIV absorption, as well as a higher incidence of LoBAL absorption, than the overall BAL quasar population. Many of the PV-detected quasars have CIV troughs that do not reach zero intensity (at velocities where PV is detected), confirming that the outflow gas only partially covers the UV continuum source. P V appears significantly in a composite spectrum of non-PV-detected BAL quasars, indicating that P V absorption (and large column densities) is much more common than indicated by our search results. Our sample of PV detections significantly increases the number of known PV detections, providing opportunities for follow-up studies to better understand BAL outflow energetics.
839. SDSS quasars with weak emission lines
ID:
ivo://CDS.VizieR/J/A+A/568/A114
Title:
SDSS quasars with weak emission lines
Short Name:
J/A+A/568/A114
Date:
21 Oct 2021
Publisher:
CDS
Description:
A tiny fraction of the quasar population shows remarkably weak emission lines. Several hypotheses have been developed, but the weak line quasar (WLQ) phenomenon still remains puzzling. The aim of this study was to create a sizeable sample of WLQs and WLQ-like objects and to evaluate various properties of this sample. We performed a search for WLQs in the spectroscopic data from the Sloan Digital Sky Survey Data Release 7 based on Kohonen self-organising maps for nearly 10^5^ quasar spectra. The final sample consists of 365 quasars in the redshift range z=0.6-4.2 (z{bar}=1.50+/-0.45) and includes in particular a subsample of 46 WLQs with equivalent widths W_MgII_<11{AA} and W_CIV_<4.8{AA} We compared the luminosities, black hole masses, Eddington ratios, accretion rates, variability, spectral slopes, and radio properties of the WLQs with those of control samples of ordinary quasars. Particular attention was paid to selection effects.
840. SDSS RM Project: CIV lags & LCs from 4yrs of data
ID:
ivo://CDS.VizieR/J/ApJ/887/38
Title:
SDSS RM Project: CIV lags & LCs from 4yrs of data
Short Name:
J/ApJ/887/38
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present reverberation-mapping (RM) lags and black hole mass measurements using the CIV{lambda}1549 broad emission line from a sample of 348 quasars monitored as a part of the Sloan Digital Sky Survey RM Project. Our data span four years of spectroscopic and photometric monitoring for a total baseline of 1300 days, allowing us to measure lags up to ~750days in the observed frame (this corresponds to a rest-frame lag of ~300days in a quasar at z=1.5 and ~190days at z=3). We report significant time delays between the continuum and the CIV{lambda}1549 emission line in 48 quasars, with an estimated false-positive detection rate of 10%. Our analysis of marginal lag measurements indicates that there are on the order of ~100 additional lags that should be recoverable by adding more years of data from the program. We use our measurements to calculate black hole masses and fit an updated CIV radius-luminosity relationship. Our results significantly increase the sample of quasars with CIV RM results, with the quasars spanning two orders of magnitude in luminosity toward the high-luminosity end of the CIV radius-luminosity relation. In addition, these quasars are located at some of the highest redshifts (z~1.4-2.8) of quasars with black hole masses measured with RM.

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