- 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.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/817/73
- Title:
- QSOs and RR Lyrae in Pan-STARRS1 3{pi} Data
- Short Name:
- J/ApJ/817/73
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In area and depth, the Pan-STARRS1 (PS1) 3{pi} survey is unique among many-epoch, multi-band surveys and has enormous potential for the all-sky identification of variable sources. PS1 has observed the sky typically seven times in each of its five bands (grizy) over 3.5 years, but unlike SDSS, not simultaneously across the bands. We developed a new approach for quantifying statistical properties of non-simultaneous, sparse, multi-color light curves through light curve structure functions, effectively turning PS1 into a {sim}35-epoch survey. We use this approach to estimate variability amplitudes and timescales for point sources brighter than r_P1_=21.5 mag in the survey. On this basis we provide a catalog of all likely variable point sources and likely QSOs in PS1.
- ID:
- ivo://CDS.VizieR/J/MNRAS/434/3104
- Title:
- QSOs SED shapes from optical to NIR
- Short Name:
- J/MNRAS/434/3104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We define a quasar-galaxy mixing diagram using the slopes of their spectral energy distributions (SEDs) from 1{mu}m to 3000{AA} and from 1 to 3{mu}m in the rest frame. The mixing diagram can easily distinguish among quasar-dominated, galaxy-dominated and reddening-dominated SED shapes. By studying the position of the 413 XMM-selected type 1 AGN in the wide-field 'Cosmic Evolution Survey' in the mixing diagram, we find that a combination of the Elvis et al. (2012ApJ...759....6E, Cat. J/ApJ/759/6) mean quasar SED with various contributions from galaxy emission and some dust reddening is remarkably effective in describing the SED shape from 0.3 to 3{mu}m for large ranges of redshift, luminosity, black hole mass and Eddington ratio of type 1 AGN. In particular, the location in the mixing diagram of the highest luminosity AGN is very close (within 1{sigma}) to that of the Elvis et al. (2012ApJ...759....6E, Cat. J/ApJ/759/6) SED template. The mixing diagram can also be used to estimate the host galaxy fraction and reddening in quasar. We also show examples of some outliers which might be AGN in different evolutionary stages compared to the majority of AGN in the quasar-host galaxy co-evolution cycle.
- ID:
- ivo://CDS.VizieR/J/AJ/137/3884
- Title:
- Quasar candidates selected from the SDSS
- Short Name:
- J/AJ/137/3884
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We explore the multidimensional, multiwavelength selection of quasars from mid-infrared (MIR) plus optical data, specifically from Spitzer-Infrared Array Camera (IRAC) and the Sloan Digital Sky Survey (SDSS). Traditionally, quasar selection relies on cuts in two-dimensional color space despite the fact that most modern surveys (optical and IR) are done in more than three bandpasses. In this paper, we apply modern statistical techniques to combined Spitzer MIR and SDSS optical data, allowing up to eight-dimensional (8-D) color selection of quasars. Using a Bayesian selection method, we catalog 5546 quasar candidates to an 8.0{mu}m depth of 56{mu}Jy over an area of ~24{deg}^2^. Roughly 70% of these candidates are not identified by applying the same Bayesian algorithm to 4-color SDSS optical data alone. The 8-D optical+MIR selection on this data set recovers 97.7% of known type 1 quasars in this area and greatly improves the effectiveness of identifying 3.5<z<5 quasars which are challenging to identify (without considerable contamination) using MIR data alone.
1335. Quasar evolution
- ID:
- ivo://CDS.VizieR/J/ApJ/269/352
- Title:
- Quasar evolution
- Short Name:
- J/ApJ/269/352
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the Bright Quasar Survey (BQS) consisting of 114 objects to an average limiting magnitude B=16.16 over an area of 10714{deg}^2^. There are 92 quasars with M_B_<-23 in the sample. We use the BQS and complete samples from published surveys to derive models of the statistical evolution of quasars. The increase of space density with redshift depends strongly on absolute luminosity, being close to zero for low-luminosity quasars. Detailed predictions are given for the distribution of redshifts and magnitudes and for the total counts based on the evolution models.
- 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.
- ID:
- ivo://CDS.VizieR/J/AJ/131/2766
- Title:
- Quasar luminosity function from SDSS-DR3
- Short Name:
- J/AJ/131/2766
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We determine the number counts and z=0-5 luminosity function for a well-defined, homogeneous sample of quasars from the Sloan Digital Sky Survey (SDSS). We conservatively define the most uniform statistical sample possible, consisting of 15343 quasars within an effective area of 1622{deg}^2^ that was derived from a parent sample of 46420 spectroscopically confirmed broad-line quasars in the 5282{deg}^2^ of imaging data from SDSS Data Release 3. The sample extends from i=15 to 19.1 at z<~3 and to i=20.2 for z>~3.
1338. Quasars from 7C survey
- ID:
- ivo://CDS.VizieR/J/MNRAS/307/293
- Title:
- Quasars from 7C survey
- Short Name:
- J/MNRAS/307/293
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe the selection of candidate radio-loud quasars obtained by cross-matching radio source positions from the low-frequency (151-MHz) 7C survey with optical positions from five pairs of EO POSS-1 plates scanned with the Cambridge Automatic Plate-measuring Machine (APM). The sky region studied is centred at RA=10h28m, DE=+41{deg} and covers ~0.057sr. We present VLA observations of the quasar candidates, and tabulate various properties derived from the radio maps. We discuss the selection criteria of the resulting '7CQ' sample of radio-loud quasars. The 70 confirmed quasars, and some fraction of the 36 unconfirmed candidates, constitute a filtered sample with the following selection criteria: 151-MHz flux density S_151_>100mJy; POSS-I E-plate magnitude E~R<20; POSS-I colour (O-E)<1.8; the effective area of the survey drops significantly below S_151_~200mJy. We argue that the colour criterion excludes few if any quasars, but note, on the basis of recent work by Willott et al. (1998MNRAS.300..625W), that the E magnitude limit probably excludes more than 50 per cent of the radio-loud quasars.
- ID:
- ivo://CDS.VizieR/J/AJ/144/49
- Title:
- Quasars from SDSS-DR7, WISE and UKIDSS surveys
- Short Name:
- J/AJ/144/49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of 37842 quasars in the Sloan Digital Sky Survey (SDSS) Data Release 7, which have counterparts within 6" in the Wide-field Infrared Survey Explorer (WISE) Preliminary Data Release. The overall WISE detection rate of the SDSS quasars is 86.7%, and it decreases to less than 50.0% when the quasar magnitude is fainter than i=20.5. We derive the median color-redshift relations based on this SDSS-WISE quasar sample and apply them to estimate the photometric redshifts of the SDSS-WISE quasars. We find that by adding the WISE W1- and W2-band data to the SDSS photometry we can increase the photometric redshift reliability, defined as the percentage of sources with photometric and spectroscopic redshift difference less than 0.2, from 70.3% to 77.2%. We also obtain the samples of WISE-detected normal and late-type stars with SDSS spectroscopy, and present a criterion in the z-W1 versus g-z color-color diagram, z-W1>0.66(g-z)+2.01, to separate quasars from stars. With this criterion we can recover 98.6% of 3089 radio-detected SDSS-WISE quasars with redshifts less than four and overcome the difficulty in selecting quasars with redshifts between 2.2 and 3 from SDSS photometric data alone. We also suggest another criterion involving the WISE color only, W1-W2>0.57, to efficiently separate quasars with redshifts less than 3.2 from stars. In addition, we compile a catalog of 5614 SDSS quasars detected by both WISE and UKIDSS surveys and present their color-redshift relations in the optical and infrared bands. By using the SDSS ugriz, UKIDSS, YJHK, and WISE W1- and W2-band photometric data, we can efficiently select quasar candidates and increase the photometric redshift reliability up to 87.0%. We discuss the implications of our results on the future quasar surveys. An updated SDSS-WISE quasar catalog consisting of 101853 quasars with the recently released WISE all-sky data is also provided.
- ID:
- ivo://CDS.VizieR/J/ApJ/753/106
- Title:
- Quasar variability with SDSS and POSS imaging
- Short Name:
- J/ApJ/753/106
- Date:
- 11 Mar 2022 15:31:25
- Publisher:
- CDS
- Description:
- We provide a quantitative description and statistical interpretation of the optical continuum variability of quasars. The Sloan Digital Sky Survey (SDSS) has obtained repeated imaging in five UV-to-IR photometric bands for 33,881 spectroscopically confirmed quasars. About 10,000 quasars have an average of 60 observations in each band obtained over a decade along Stripe 82 (S82), whereas the remaining ~25,000 have 2-3 observations due to scan overlaps. The observed time lags span the range from a day to almost 10 years, and constrain quasar variability at rest-frame time lags of up to 4 years, and at rest-frame wavelengths from 1000{AA} to 6000{AA}. We publicly release a user-friendly catalog of quasars from the SDSS Data Release 7 that have been observed at least twice in SDSS or once in both SDSS and the Palomar Observatory Sky Survey, and we use it to analyze the ensemble properties of quasar variability. Based on a damped random walk (DRW) model defined by a characteristic timescale and an asymptotic variability amplitude that scale with the luminosity, black hole mass, and rest wavelength for individual quasars calibrated in S82, we can fully explain the ensemble variability statistics of the non-S82 quasars such as the exponential distribution of large magnitude changes. All available data are consistent with the DRW model as a viable description of the optical continuum variability of quasars on timescales of ~5-2000 days in the rest frame. We use these models to predict the incidence of quasar contamination in transient surveys such as those from the Palomar Transient Factory and Large Synoptic Survey Telescope.
