- ID:
- ivo://CDS.VizieR/J/A+A/618/A144
- Title:
- QSO candidates catalog with APOP & ALLWISE (QCC)
- Short Name:
- J/A+A/618/A144
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Quasars are spatially stationary, and they are essential objects in astrometry when defining reference frames. However, the census of quasars is far from complete. Mid-infared colors can be used to find quasar candidates because AGNs show a peculiar appearance in mid-infrared color, but these methods are incapable of separating quasars from AGNs.The aim of our study is to use astrometric and mid-infrared methods to select quasars and get a reliable quasar candidates catalog. We used a near-zero proper motion criterion in conjuction with WISE (all-sky Wide-field Infrared Survey Explorer) [W1-W2] color to select quasar candidates. The [W1-W2] color criterion is defined by the linear boundary of two samples: LAMOST DR5 quasars, which serve as the quasar sample, and LAMOST DR5 stars/galaxies, which serve as the non-quasar sample. The contamination and completeness are evaluated. We present a catalog of 662753 quasar candidates, with a completeness of about 75% and a reliability of 77.2%.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/747/107
- Title:
- QSO Candidates in the MACHO LMC database
- Short Name:
- J/ApJ/747/107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog the 2566 QSO candidates in the MACHO LMC database. In these catalogs, we complied number of properties of the objects including RA, Dec, crossmatched IDs with several catalogs, magnitudes, photometric redshifts, etc. See Kim et al. (2011ApJ...735...68K) for the SVM (a.k.a. Support Vector Machine, a supervised machine learning algorithm) QSO classification model based on the time variability of lightcurves. We used the model to select the 2566 QSO candidates. In this work, we employed multiple diagnostics such as X-ray flux, mid-IR color and AGN SED fitting in order to select 663 promising QSO candidates among the 2,566 candidates. These candidates are flagged in the catalog. We calibrated the MACHO RA and Dec of the candidates using the UCAC3 catalog and improved the average astrometric accuracy from ~3" to ~0.5".
- ID:
- ivo://CDS.VizieR/J/MNRAS/396/223
- Title:
- QSO candidates selection in VO era
- Short Name:
- J/MNRAS/396/223
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a method for the photometric selection of candidate quasars in multiband surveys. The method makes use of a priori knowledge derived from a subsample of spectroscopic confirmed quasi-stellar objects (QSOs) to map the parameter space. The disentanglement of QSOs candidates and stars is performed in the colour space through the combined use of two algorithms, the probabilistic principal surfaces and the negative entropy clustering, which are for the first time used in an astronomical context. Both methods have been implemented in the voneural package on the Astrogrid Virtual Observatory platform. Even though they belong to the class of the unsupervised clustering tools, the performances of the method are optimized by using the available sample of confirmed quasars and it is therefore possible to learn from any improvement in the available 'base of knowledge'. The method has been applied and tested on both optical and optical plus near-infrared data extracted from the visible Sloan Digital Sky Survey (SDSS) and infrared United Kingdom Infrared Deep Sky Survey-Large Area Survey public data bases. In all cases, the experiments lead to high values of both efficiency and completeness, comparable if not better than the methods already known in the literature. A catalogue of optical candidate QSOs extracted from the SDSS Data Release 7 Legacy photometric data set has been produced.
- ID:
- ivo://CDS.VizieR/J/ApJ/710/1498
- Title:
- QSO luminosity function at z~4
- Short Name:
- J/ApJ/710/1498
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The evolution of the quasar luminosity function (QLF) is one of the basic cosmological measures providing insight into structure formation and mass assembly in the universe. We have conducted a spectroscopic survey to find faint quasars (-26.0<M_1450_<-22.0) at redshifts z=3.8-5.2 in order to measure the faint end of the QLF at these early times. Using available optical imaging data from portions of the NOAO Deep Wide-Field Survey and the Deep Lens Survey, we have color-selected quasar candidates in a total area of 3.76deg^2^. Thirty candidates have R<=23mag. We conducted spectroscopic follow-up for 28 of our candidates and found 23 QSOs, 21 of which are reported here for the first time, in the 3.74<z<5.06 redshift range.
- 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.
- 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.
1389. 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.
