- ID:
- ivo://CDS.VizieR/J/MNRAS/399/2231
- Title:
- SDSS DR5 BALQSO catalog
- Short Name:
- J/MNRAS/399/2231
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We apply a recently developed method for classifying broad absorption line quasars (BALQSOs) to the latest QSO catalogue constructed from Data Release 5 of the Sloan Digital Sky Survey. Our new hybrid classification method combines the power of simple metrics, supervised neural networks and visual inspection. The resulting BALQSO catalogue is both more complete and more robust than all previous BALQSO catalogues, containing 3552 sources selected from a parent sample of 28421 QSOs in the redshift range 1.7<z<4.2. This equates to a raw BAL QSO fraction of 12.5%. In the process of constructing a robust catalogue we shed light on the main problems encountered when dealing with BALQSO classification, in particular when the astronomical objects in question do not yet have a formal definition as is the case for BALQSOs. This introduces some subjectivity on what is meant by BALQSO, and because of this we also provide meta-data of our catalogue, comprising our whole parent sample which can be used to quickly isolate and explore various sub-samples.
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772. SDSS DR2 BAL QSOs
- ID:
- ivo://CDS.VizieR/J/ApJ/665/990
- Title:
- SDSS DR2 BAL QSOs
- Short Name:
- J/ApJ/665/990
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have investigated a sample of 5088 quasars from the SDSS DR2 in order to determine how the frequency and properties of BALs depend on black hole mass, bolometric luminosity, Eddington fraction (L/L_Edd_), and spectral slope. We focus only on high-ionization BALs and find a number of significant results. While quasars accreting near the Eddington limit are more likely to show BALs than lower L/LEdd systems, BALs are present in quasars accreting at only a few percent Eddington. We find a stronger effect with bolometric luminosity, such that the most luminous quasars are more likely to show BALs. There is an additional effect, previously known, that BAL quasars are redder on average than unabsorbed quasars. The strongest effects involving the quasar physical properties and BAL properties are related to terminal outflow velocity. Maximum observed outflow velocities increase with both the bolometric luminosity and the blueness of the spectral slope, suggesting that the ultraviolet luminosity to a great extent determines the acceleration. These results support the idea of outflow acceleration via ultraviolet line scattering.
- ID:
- ivo://CDS.VizieR/J/ApJ/804/L15
- Title:
- SDSS-DR7 broad-line QSOs
- Short Name:
- J/ApJ/804/L15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The diverse properties of broad-line quasars appear to follow a well-defined main sequence along which the optical FeII strength increases. It has been suggested that this sequence is mainly driven by the Eddington ratio (L/L_Edd_) of the black hole (BH) accretion. Shen & Ho (2014Natur.513..210S) demonstrated with quasar clustering analysis that the average BH mass decreases with increasing FeII strength when quasar luminosity is fixed, consistent with this suggestion. Here we perform an independent test by measuring the stellar velocity dispersion {sigma}_*_ (hence, the BH mass via the M-{sigma}_*_ relation) from decomposed host spectra in low-redshift Sloan Digital Sky Survey quasars. We found that at fixed quasar luminosity, {sigma}_*_ systematically decreases with increasing FeII strength, confirming that the Eddington ratio increases with FeII strength. We also found that at fixed luminosity and FeII strength, there is little dependence of {sigma}_*_ on the broad H{beta} FWHM. These new results reinforce the framework that the Eddington ratio and orientation govern most of the diversity seen in broad-line quasar properties.
- ID:
- ivo://CDS.VizieR/J/MNRAS/450/3893
- Title:
- SDSS DR10 catalogue of candidate quasars
- Short Name:
- J/MNRAS/450/3893
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We discuss whether modern machine learning methods can be used to characterize the physical nature of the large number of objects sampled by the modern multi-band digital surveys. In particular, we applied the MLPQNA (Multi Layer Perceptron with Quasi Newton Algorithm) method to the optical data of the Sloan Digital Sky Survey - Data Release 10, investigating whether photometric data alone suffice to disentangle different classes of objects as they are defined in the SDSS spectroscopic classification. We discuss three groups of classification problems: (i) the simultaneous classification of galaxies, quasars and stars; (ii) the separation of stars from quasars; (iii) the separation of galaxies with normal spectral energy distribution from those with peculiar spectra, such as starburst or starforming galaxies and AGN. While confirming the difficulty of disentangling AGN from normal galaxies on a photometric basis only, MLPQNA proved to be quite effective in the three-class separation. In disentangling quasars from stars and galaxies, our method achieved an overall efficiency of 91.31% and a QSO class purity of ~95%. The resulting catalogue of candidate quasars/AGNs consists of ~3.6 million objects, of which about half a million are also flagged as robust candidates.
- ID:
- ivo://CDS.VizieR/J/MNRAS/477/5625
- Title:
- SDSSDR12 eclipsing damped Lyalpha systems
- Short Name:
- J/MNRAS/477/5625
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of our automatic search for proximate damped Ly{alpha} absorption (PDLA) systems in the quasar spectra from the Sloan Digital Sky Survey Data Release 12. We constrain our search to those PDLAs lying within 1500km/s from the quasar to make sure that the broad DLA absorption trough masks most of the strong Ly{alpha} emission from the broad-line region (BLR) of the quasar. When the Ly{alpha} emission from the BLR is blocked by these so-called eclipsing DLAs, narrow Ly{alpha} emission from the host galaxy could be revealed as a narrow emission line (NEL) in the DLA trough. We define a statistical sample of 399 eclipsing DLAs with logN(HI)>=21.10. We divide our statistical sample into three subsamples based on the strength of the NEL detected in the DLA trough. By studying the stacked spectra of these subsamples, we found that absorptions from high ionization species are stronger in DLAs with stronger NEL in their absorption core. Moreover, absorption from the excited states of species like SIII are also stronger in DLAs with stronger NEL. We also found no correlation between the luminosity of the Ly{alpha} NEL and the quasar luminosity. These observations are consistent with a scenario in which the DLAs with stronger NEL are denser and physically closer to the quasar. We propose that these eclipsing DLAs could be the product of the interaction between infalling and outflowing gas. High-resolution spectroscopic observation would be needed to shed some light on the nature of these eclipsing DLAs.
- ID:
- ivo://CDS.VizieR/J/MNRAS/397/1713
- Title:
- SDSS DR3 flat-spectrum radio quasars
- Short Name:
- J/MNRAS/397/1713
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We constructed a sample of 185 flat-spectrum radio quasars (FSRQs) by cross-correlating Shen et al.'s (2006MNRAS.369.1639S) Sloan Digital Sky Survey Data Release 3 (SDSS DR3) X-ray quasar sample with the Faint Images of the Radio Sky at Twenty Centimeters (FIRST) and Green Bank 6-cm survey (GB6) radio catalogues. From the spectral energy distribution (SED) constructed using multi-band (radio, UV, optical, infrared and X-ray) data, we derived the synchrotron peak frequency and peak luminosity. The black hole mass MBH and the broad-line region (BLR) luminosity (then the bolometric luminosity Lbol) were obtained by measuring the linewidth and strength of broad emission lines from SDSS spectra. We define a subsample of 118 FSRQs for which non-thermal jet emission is thought to dominate over thermal emission from the accretion disc and host galaxy.
- ID:
- ivo://CDS.VizieR/J/AJ/142/122
- Title:
- SDSS DR7 galaxy/QSOs pairs
- Short Name:
- J/AJ/142/122
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The aim of this project is to identify low-redshift host galaxies of quasar absorption-line systems by selecting galaxies that are seen in projection onto quasar sightlines. To this end, we use the Seventh Data Release of the Sloan Digital Sky Survey to construct a parent sample of 97489 galaxy/quasar projections at impact parameters of up to 100 kpc to the foreground galaxy. We then search the quasar spectra for absorption-line systems of CaII and NaI within +/-500km/s1 of the galaxy's velocity. This yields 92 CaII and 16 NaI absorption systems.
- ID:
- ivo://CDS.VizieR/J/ApJS/194/42
- Title:
- SDSS-DR3 MgII-based black hole masses
- Short Name:
- J/ApJS/194/42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present MgII-based black hole (BH) mass estimates for 27602 quasars with rest-frame UV spectra available in the Sloan Digital Sky Survey Data Release Three (Cat. II/259; superseded by II/294). This estimation is possible due to the existence of an empirical correlation between the radius of the broad-line region (BLR) and the continuum luminosity at 3000{AA}. We regenerate this correlation by applying our measurement method to UV spectra of low-redshift quasars in the Hubble Space Telescope/International Ultraviolet Explorer databases which have corresponding reverberation mapping estimates of the H{beta} BLR's radius. Our mass estimation method uses the line dispersion rather than the full width at half-maximum of the low-ionization MgII emission line.
- ID:
- ivo://CDS.VizieR/J/AJ/140/817
- Title:
- SDSS-DR3 OVI QSOs absorbers
- Short Name:
- J/AJ/140/817
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of a systematic search for signatures of metal lines in quasar spectra of the Sloan Digital Sky Survey (SDSS) data release 3 (DR3), focusing on finding intervening absorbers via detection of their OVI doublet. Here, we present the search algorithm and criteria for distinguishing candidates from spurious Ly{alpha} forest lines. In addition, we compare our findings with simulations of the Ly{alpha} forest in order to estimate the detectability of OVI doublets over various redshift intervals. We have obtained a sample of 1756 OVI doublet candidates with rest-frame equivalent width (EW)>=0.05{AA} in 855 active galactic nuclei spectra (out of 3702 objects with redshifts in the accessible range for OVI detection).
- ID:
- ivo://CDS.VizieR/J/MNRAS/354/L31
- Title:
- SDSS DR2 QSO and DLA properties
- Short Name:
- J/MNRAS/354/L31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use Sloan Digital Sky Survey (SDSS) Data Release 2 quasi-stellar object (QSO) spectra to constrain the dust-reddening caused by intervening damped Lyman {alpha} systems (DLAs). Comparing the spectral index distribution of a 70 sight-line DLA sample with that of a large control sample reveals no evidence for dust-reddening at z~3.
