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5381. QSO MgII absorption line systems
ID:
ivo://CDS.VizieR/J/AJ/106/848
Title:
QSO MgII absorption line systems
Short Name:
J/AJ/106/848
Date:
21 Oct 2021
Publisher:
CDS
Description:
The results of a large R-band imaging survey of 71 bright (m(V)<18) quasars are presented. The quasars were chosen from published samples which have intermediate resolution optical spectroscopy available, so the presence of low redshift Mg II absorption lines can be determined. We have searched our data for galaxies close to the line-of-sight to the quasars, which we might be able to identify with the absorption systems. We find a high coincidence between galaxies very near the line-of-sight and quasars showing absorption systems in their spectra, a result consistent with other studies. These galaxies have a mean luminosity of 0.5L_star_ (assuming they lie at the absorption redshift). The distribution of impact parameters between the galaxies and the quasars extends with a flat distribution to large radii (>30h^-1^kpc). This suggests that the absorption systems may not be gravitationally bound to the observed galaxies, but may be part of larger extended systems. We also find a significant number of galaxies near the line-of-sight to the quasar where no absorption is seen in the quasar spectrum. The selection of our quasars is unbiased with respect to galaxies near the line-of-sight, so we can compare the observed number of absorption systems to that predicted by a simple model with a constant covering factor in Mg II absorbing gas within a maximum radius of each detected galaxy. The model is consistent with a covering factor of unity, but allowing for incompleteness in the detection of galaxies, the covering factor is less than unity. The redshifts of the galaxies are required to confirm this result.
5382. QSO 2237+0305 photometry and light curves
ID:
ivo://CDS.VizieR/J/A+A/637/A89
Title:
QSO 2237+0305 photometry and light curves
Short Name:
J/A+A/637/A89
Date:
21 Oct 2021
Publisher:
CDS
Description:
Quasar microlensing offers a unique opportunity to resolve tiny sources in distant active galactic nuclei and study compact object populations in lensing galaxies. We therefore searched for microlensing-induced variability of the gravitationally lensed quasar QSO 2237+0305 (Einstein Cross) using 4374 optical frames taken with the 2.0m Liverpool Telescope and the 1.5m Maidanak Telescope. These gVrRI frames over the 2006-2019 period were homogeneously processed to generate accurate long-term multi-band light curves of the four quasar images A-D. Through difference light curves, we found strong microlensing signatures. We then focused on the analytical modelling of two putative caustic-crossing events in image C, finding compelling evidence that this image experienced a double caustic crossing. Additionally, our overall results indicate that a standard accretion disc accounts reasonably well for the brightness profile of UV continuum emission sources and for the growth in source radius when the emission wavelength increases: R_{lambda}_{prop.to}{lambda}^{alpha}^, {alpha}=1.33+/-0.09. However, we caution that numerical microlensing simulations are required before firm conclusions can be reached on the UV emission scenario because the VRI-band monitoring during the first caustic crossing and one of our two {alpha} indicators lead to a few good solutions with {alpha}~~1.
5383. QSO properties from SDSS-DR7
ID:
ivo://CDS.VizieR/J/ApJS/194/45
Title:
QSO properties from SDSS-DR7
Short Name:
J/ApJS/194/45
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a compilation of properties of the 105783 quasars in the Sloan Digital Sky Survey Data Release 7 (DR7) quasar catalog (Cat. VII/260). In this product, we compile continuum and emission line measurements around the H{alpha}, H{beta}, MgII, and CIV regions, as well as other quantities such as radio properties, and flags indicating broad absorption line quasars, disk emitters, etc. We also compile virial black hole mass estimates based on various calibrations. For the fiducial virial mass estimates we use the Vestergaard & Peterson (VP06; 2006ApJ...641..689V) calibrations for H{beta} and CIV, and our own calibration for MgII which matches the VP06 H{beta} masses on average. We describe the construction of this catalog and discuss its limitations.
5384. QSO selection based on photometric variability
ID:
ivo://CDS.VizieR/J/ApJ/728/26
Title:
QSO selection based on photometric variability
Short Name:
J/ApJ/728/26
Date:
21 Oct 2021
Publisher:
CDS
Description:
We develop a method for separating quasars from other variable point sources using Sloan Digital Sky Survey (SDSS) Stripe 82 light-curve data for ~10000 variable objects. To statistically describe quasar variability, we use a damped random walk (DRW) model parametrized by a damping timescale, {tau}, and an asymptotic amplitude (structure function), SF_{infinite}_. With the aid of an SDSS spectroscopically confirmed quasar sample, we demonstrate that variability selection in typical extragalactic fields with low stellar density can deliver complete samples with reasonable purity (or efficiency, E). Compared to a selection method based solely on the slope of the structure function, the inclusion of the {tau} information boosts E from 60% to 75% while maintaining a highly complete sample (98%) even in the absence of color information. For a completeness of C=90%, E is boosted from 80% to 85%. Conversely, C improves from 90% to 97% while maintaining E=80% when imposing a lower limit on {tau}. With the aid of color selection, the purity can be further boosted to 96%, with C=93%. Hence, selection methods based on variability will play an important role in the selection of quasars with data provided by upcoming large sky surveys, such as Pan-STARRS and the Large Synoptic Survey Telescope (LSST). In summary, given an adequate survey cadence, photometric variability provides an even better method than color selection for separating quasars from stars.
5385. QSOs in 2MASS second incremental data release
ID:
ivo://CDS.VizieR/J/AJ/121/2843
Title:
QSOs in 2MASS second incremental data release
Short Name:
J/AJ/121/2843
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using the 2MASS Second Incremental Data Release (Cat. <B/2mass>), we have searched for near-infrared counterparts to 13214 quasars from the Veron-Cetty & Veron (Cat. <VII/215>) catalog. We have detected counterparts within 4" for 2277 of the approximately 6320 quasars within the area covered by the 2MASS Second Incremental Data Release. Only 1.6% of these are expected to be chance coincidences. Though this sample is heterogeneous, we find that known radio-loud quasars are more likely to have large near-infrared-to-optical luminosity ratios than radio-quiet quasars are, at a statistically significant level. This is consistent with dust-reddened quasars being more common in radio-selected samples than in optically selected samples, due to stronger selection effects against dust-reddened quasars in the latter. We also find a statistically significant dearth of optically luminous quasars with large near-infrared-to-optical luminosity ratios. This can be explained in a dust obscuration model but not in a model where synchrotron emission extends from the radio into the near-infrared and creates such large ratios. We also find that selection of quasar candidates from the B-J/J-K color-color diagram, modeled on the V-J/J-K selection method of Warren, Hewett, & Foltz, is likely to be more sensitive to dust-obscured quasars than selection using only infrared-infrared colors.
5386. QSOs in the M3 field
ID:
ivo://CDS.VizieR/J/A+A/392/851
Title:
QSOs in the M3 field
Short Name:
J/A+A/392/851
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present results from a variability and proper motion (VPM) search for QSOs in the field around M3. The VPM search is demonstrated to be powerful technique for efficiently finding QSOs without major selection effects with regard to the spectral energy distribution. Remarkably, the properties of the VPM QSOs do not significantly differ from those of samples from more conventional optical search techniques. The lightcurves of the QSOs from the resulting sample provide an interesting data set for the statistical investigation of QSO long-term variability.
5387. QSOs selection from SDSS and WISE
ID:
ivo://CDS.VizieR/J/ApJS/219/39
Title:
QSOs selection from SDSS and WISE
Short Name:
J/ApJS/219/39
Date:
21 Oct 2021
Publisher:
CDS
Description:
We identify 885503 type 1 quasar candidates to i<~22 using the combination of optical and mid-IR photometry. Optical photometry is taken from the Sloan Digital Sky Survey-III: Baryon Oscillation Spectroscopic Survey (SDSS-III/BOSS), while mid-IR photometry comes from a combination of data from the Wide-field Infrared Survey Explorer (WISE) "AllWISE" data release and several large-area Spitzer Space Telescope fields. Selection is based on a Bayesian kernel density algorithm with a training sample of 157701 spectroscopically confirmed type 1 quasars with both optical and mid-IR data. Of the quasar candidates, 733713 lack spectroscopic confirmation (and 305623 are objects that we have not previously classified as photometric quasar candidates). These candidates include 7874 objects targeted as high-probability potential quasars with 3.5<z<5 (of which 6779 are new photometric candidates). Our algorithm is more complete to z>3.5 than the traditional mid-IR selection "wedges" and to 2.2<z<3.5 quasars than the SDSS-III/BOSS project. Number counts and luminosity function analysis suggest that the resulting catalog is relatively complete to known quasars and is identifying new high-z quasars at z>3. This catalog paves the way for luminosity-dependent clustering investigations of large numbers of faint, high-redshift quasars and for further machine-learning quasar selection using Spitzer and WISE data combined with other large-area optical imaging surveys.
5388. Quadruply lensed quasar WFI2033-4723 light curves
ID:
ivo://CDS.VizieR/J/A+A/629/A97
Title:
Quadruply lensed quasar WFI2033-4723 light curves
Short Name:
J/A+A/629/A97
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present new measurements of the time delays of WFI2033-4723. The data sets used in this work include 14 years of data taken at the 1.2m Leonhard Euler Swiss telescope, 13 years of data from the SMARTS 1.3m telescope at Las Campanas Observatory and a single year of high-cadence and high-precision monitoring at the MPIA 2.2m telescope. The time delays measured from these different data sets, all taken in the R-band, are in good agreement with each other and with previous measurements from the literature. Combining all the time-delay estimates from our data sets results in Dt_AB_=36.2_-0.8_^+0.7^days (2.1% precision), Dt_AC_=-23.3_-1.4_^+1.2^days (5.6%) and Dt_BC_=-59.4_-1.3_^+1.3^days (2.2%). In addition, the close image pair A1-A2 of the lensed quasars can be resolved in the MPIA 2.2m data. We measure a time delay consistent with zero in this pair of images. We also explore the prior distributions of microlensing time-delay potentially affecting the cosmological time-delay measurements of WFI2033-4723. There is however no strong indication in our measurements that microlensing time delay is neither present nor absent. This work is part of a H0LiCOW series focusing on measuring the Hubble constant from WFI2033-4723.
5389. Quasar from SDSS and UKIDSS
ID:
ivo://CDS.VizieR/J/MNRAS/406/1583
Title:
Quasar from SDSS and UKIDSS
Short Name:
J/MNRAS/406/1583
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a sample of 8498 quasars with both Sloan Digital Sky Survey (SDSS) ugriz optical and United Kingdom Infrared Telescope (UKIRT) Infrared Deep Sky Survey (UKIDSS) YJHK near-infrared (near-IR) photometric data. With this sample, we obtain the median colour-z relations based on 7400 quasars with magnitude uncertainties less than 0.1mag in all bands. By analysing the quasar colours, we propose an empirical criterion in the Y-K versus g-z colour-colour diagram to separate stars and quasars with redshift z<4, and two other criteria for selecting high-redshift quasars. Using the SDSS-UKIDSS colour-z relations, we estimate the photometric redshifts of 8498 SDSS-UKIDSS quasars, and find that 85.0 per cent of them are consistent with the spectroscopic redshifts within |{Delta}z|<0.2, which leads to a significant increase of the photometric redshift accuracy from that based on the SDSS colour-z relations only. As two tests, we compare our colour-selection criterion with a small UKIDSS/EDR quasar/star sample and a sample of 4671 variable sources in the SDSS Stripe 82 region with both SDSS and UKIDSS data. We find that they can be clearly divided into two classes (quasars and stars) by our criterion in the Y-K versus g-z plot.
5390. Quasar luminosity function
ID:
ivo://CDS.VizieR/J/MNRAS/260/202
Title:
Quasar luminosity function
Short Name:
J/MNRAS/260/202
Date:
21 Oct 2021
Publisher:
CDS
Description:
A sample of quasars is selected from a 10-yr sequence of 30 UK Schmidt plates. Luminosity functions are derived in several redshift intervals, which in each case show a featureless power-law rise towards low luminosities. There is no sigh of the 'break' found in the recent UVX sample of Boyle, Shanks & Peterson. It is suggested that reasons for the disagreement are connected with biases in the selection of the UVX sample. The question of the nature of quasar evolution appears to be still unresolved.