- 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.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/452/4153
- Title:
- SDSS DR12 QSOs [OIII] doublet
- Short Name:
- J/MNRAS/452/4153
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- From the Sloan Digital Sky Survey (SDSS) Data Release 12, which covers the full Baryonic Oscillation Spectroscopic Survey (BOSS) footprint, we investigate the possible variation of the fine-structure constant over cosmological time-scales. We analyse the largest quasar sample considered so far in the literature, which contains 13175 spectra (10363 from SDSS-III/BOSS DR12+2812 from SDSS-II DR7) with redshift z<1. We apply the emission-line method on the [OIII] doublet ({lambda}{lambda}4960, 5008{AA}) and obtain {Delta}{alpha}/{alpha}=(0.9+/-1.8)x10^-5^ for the relative variation of the fine-structure constant. We also investigate the possible sources of systematics: misidentification of the lines, sky OH lines, H{beta} and broad line contamination, Gaussian and Voigt fitting profiles, optimal wavelength range for the Gaussian fits, chosen polynomial order for the continuum spectrum, signal-to-noise ratio and good quality of the fits. The uncertainty of the measurement is dominated by the sky subtraction. The results presented in this work, being systematics limited, have sufficient statistics to constrain robustly the variation of the fine-structure constant in redshift bins ({Delta}z~0.06) over the last 7.9Gyr. In addition, we study the [NeIII] doublet ({lambda}{lambda}3869, 3968{AA}) present in 462 quasar spectra and discuss the systematic effects on using these emission lines to constrain the fine-structure constant variation. Better constraints on {Delta}{alpha}/{alpha}(<10^-6^) using the emission-line method would be possible with high-resolution spectroscopy and large galaxy/qso surveys.
- ID:
- ivo://CDS.VizieR/J/MNRAS/464/553
- Title:
- SDSS DR7 QSOs spectral doppelgangers
- Short Name:
- J/MNRAS/464/553
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The spectrum of a quasar contains important information about its properties. Thus, it can be expected that two quasars with similar spectra will have similar properties, but just how similar has not before been quantified. Here we compare the ultraviolet spectra of a sample of 5553 quasars from Data Release 7 of the Sloan Digital Sky Survey, focusing on the 1350{AA}<={lambda}<=2900{AA} rest-frame region which contains prominent emission lines from SiIV, OIV], CIV, CIII], and MgII species. We use principal component analysis to determine the dominant components of spectral variation, as well as to quantitatively measure spectral similarity. As suggested by both the Baldwin effect and modified Baldwin effect, quasars with similar spectra have similar properties: bolometric luminosity, Eddington fraction, and black hole mass. The latter two quantities are calculated from the luminosity in conjunction with spectral features, and the variation between quasars with virtually identical spectra (which we call doppelgangers) is driven by the variance in the luminosity plus measurement uncertainties. In the doppelgangers the luminosity differences show 1{sigma} uncertainties of 57 per cent (or 0.63mag) and ~70 per cent 1{sigma} uncertainties for mass and Eddington fraction. Much of the difference in luminosities may be attributable to time lags between the spectral lines and the continuum. Furthermore, we find that suggestions that the mostly highly accreting quasars should be better standard candles than other quasars are not borne out for doppelgangers. Finally, we discuss the implications for using quasars as cosmological probes and the nature of the first two spectral principal components.
- ID:
- ivo://CDS.VizieR/J/ApJ/819/154
- Title:
- SDSS-DR7 QSOs with X-ray and UV luminosities
- Short Name:
- J/ApJ/819/154
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The observed relation between the soft X-ray and the optical-ultraviolet emission in active galactic nuclei (AGNs) is nonlinear and it is usually parametrized as a dependence between the logarithm of the monochromatic luminosity at 2500{AA} and at 2keV. Previous investigations have found that the dispersion of this relation is rather high (~0.35-0.4 in log units), which may be caused by measurement uncertainties, variability, and intrinsic dispersion due to differences in the AGN physical properties (e.g., different accretion modes). We show that, once optically selected quasars with homogeneous SED and X-ray detection are selected, and dust reddened and/or gas obscured objects are not included, the measured dispersion drops to significantly lower values (i.e., ~0.21-0.24dex). We show that the residual dispersion is due to some extent to variability, and to remaining measurement uncertainties. Therefore, the real physical intrinsic dispersion should be <0.21dex. Such a tight relation, valid over four decades in luminosity, must be the manifestation of an intrinsic (and universal) physical relation between the disk, emitting the primary radiation, and the hot electron corona emitting X-rays.
- ID:
- ivo://CDS.VizieR/VII/252
- Title:
- SDSS-DR5 quasar catalog
- Short Name:
- VII/252
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The fourth edition of the Sloan Digital Sky Survey (SDSS) Quasar Catalog, made from the SDSS Fifth Data Release, contains 77,429 objects; this is an increase of over 30,000 entries since the previous edition (Schneider et al., Cat. <VII/243>). The catalog consists of the objects in the SDSS Fifth Data Release that have luminosities larger than M_i_=-22.0 (in a cosmology with Ho=70km.s-1.Mpc-1, {Omega}_M_=0.3, and {Omega}_{Lambda}_=0.7), have at least one emission line with FWHM larger than 1000km.s-1 or have interesting or complex absorption features, are fainter than i~15.0, and have highly reliable redshifts. The area covered by the catalog is about 5740deg^2^. The quasar redshifts range from 0.08 to 5.41, with a median value of 1.48; the catalog includes 891 quasars at redshifts greater than 4, of which 36 are at redshifts greater than 5. Approximately half of the catalog quasars have i<19; nearly all have i<21. For each object the catalog presents positions accurate to better than 0.2" rms per coordinate, five-band (ugriz) CCD-based photometry with typical accuracy of 0.03mag, and information on the morphology and selection method. The catalog also contains basic radio, near-infrared, and X-ray emission properties of the quasars, when available, from other large-area surveys. The calibrated digital spectra cover the wavelength region 3800-9200{AA} at a spectral resolution of about 2000; the spectra can be retrieved from the public database using the information provided in the catalog. The average SDSS colors of quasars as a function of redshift, derived from the catalog entries, are presented in tabular form. Approximately 96% of the objects in the catalog were discovered by the SDSS.
- ID:
- ivo://CDS.VizieR/J/A+A/631/A46
- Title:
- SDSS DR10 radio-loud quasars sample
- Short Name:
- J/A+A/631/A46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of a sample of 223 radio loud quasars (up to redshift <0.3) in order to investigate their spectral properties. Twenty-six of these radio loud quasars are identified as Flat Spect rum Radio Quasars (FSRQs) and fifty-four are identified as Steep Spectrum Radio Quasars (SSRQs) based on their radio spectral index. We study the [OIII] line properties of these quasars to investigate the origin and properties of blue wings (shift of the profile towards lower wavelengths) and blue outliers (shift of the whole spectroscopic feature). Most of the quasars show blue wings with velocities up to 420km/s. We find that around 17% of the quasars show outliers with velocities spanning 4 19 to -315km/s. Finally, we revisit the M_BH_-{sigma} relation of our sample using [SII]{lambda}6716, 6731 and [OIII] linewidths as surrogates for stellar velocity dispersions, {sigma}, to investigate their location on the M_BH_-{sigma} relation for quiescent galaxies. Due to strong blending of [SII] with H_{alpha}_, we could estimate {sigma}_[SII]_ of only 123 quasars. We find that the radio-loud quasars do not show a relationship between M_BH_ and {sigma}_[SII]/[OIII]_ up to a redshift of 0.3, although they cluster around the local relation. We find an overall offset of 0.12+/-0.05dex of our sample of radio loud quasars from the M_BH_-{sigma} relation of quiescent galaxies. Quasars in our highest redshift bin (z=0.25-0.3) show a deviation of ~0.33+/-0.06dex with respect to the local relation. Implications of the results are discussed.
- ID:
- ivo://CDS.VizieR/J/ApJ/639/766
- Title:
- SDSS-DR3 strong MgII absorbers
- Short Name:
- J/ApJ/639/766
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of two complementary investigations into the nature of strong (rest equivalent width, Wr>1.0{AA}) MgII absorption systems at high redshift. The first line of questioning examines the complete Sloan Digital Sky Survey Data Release 3 set of quasar spectra to determine the evolution of the incidence of strong MgII absorption. This search resulted in 7421 confirmed MgII systems of Wr>1.0{AA}, yielding a >95% complete statistical sample of 4835 absorbers (systems detected in S/N>7 spectral regions) spanning a redshift range 0.35<z<2.3.
- ID:
- ivo://CDS.VizieR/J/ApJ/680/169
- Title:
- SDSS DR5 virial black hole masses
- Short Name:
- J/ApJ/680/169
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We compile black hole (BH) masses for ~60000 quasars in the redshift range 0.1~<z~<4.5 included in the Fifth Data Release of the Sloan Digital Sky Survey (Schneider et al. 2007, Cat. VII/252), using virial BH mass estimators based on the H{beta}, MgII, and CIV emission lines.
- ID:
- ivo://CDS.VizieR/J/A+A/630/A110
- Title:
- SDSS-FIRST quasar sample study
- Short Name:
- J/A+A/630/A110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- When can an active galactic nucleus (AGN) be considered radio-loud? Following the established view of the AGNs inner workings, an AGN is radio-loud if associated with relativistic ejections emitting a radio synchrotron spectrum (i.e., it is a "jetted" AGN). In this paper we exploit the AGN main sequence that offers a powerful tool to contextualize radio properties. If large samples of optically-selected quasars are considered, AGNs are identified as radio-loud if their Kellermann's radio loudness ratio R_K_>10. Our aims are to characterize the optical properties of different classes based on radioloudness within the main sequence and to test whether the condition R_K_>10 is sufficient for the identification of RL AGNs, since the origin of relatively strong radio emission may not be necessarily due to relativistic ejection. A sample of 355 quasars was selected by cross-correlating the FIRST survey with the SDSS DR14 quasar catalog. We classified the optical spectra according to their spectral types along the main sequence of quasars. For each spectral type, we distinguished compact and extended morphology (providing a FIRST-based atlas of radio maps in the latter case), and three classes of radio-loudness: detected (specific flux ratio in the g band and at 1.4GHz, R_K'_<10), intermediate (10R_K'_<70), and radio loud (R_K'_>=70). The analysis revealed systematic differences between radio-detected (i.e., radio-quiet), radio-intermediate, and radio-loud in each spectral type along the main sequence. We show that spectral bins that contain the extreme Population A sources have radio power compatible with emission by mechanisms ultimately due to star formation processes. Radio-loud sources of Population B are characteristically jetted. Their broad H{beta} profiles can be interpreted as due to a binary broad-line region. We suggest that RL Population B sources should be preferential targets for the search of black hole binaries, and present a sample of binary black hole AGN candidates. The validity of the Kellermann's criterion may be dependent on the source location along the quasar main sequence. The consideration of the MS trends allowed to distinguish between sources whose radio emission mechanisms is "jetted" from the ones where the mechanism is likely to be fundamentally different.
- ID:
- ivo://CDS.VizieR/J/AJ/140/1987
- Title:
- SDSS-GALEX QSO catalog
- Short Name:
- J/AJ/140/1987
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We discuss a sample of ~60000 objects from the combined Sloan Digital Sky Survey-Galaxy Evolution Explorer (SDSS-GALEX) database with UV-optical colors that should isolate QSOs in the redshift range 0.5-1.5. We use SDSS spectra of a subsample of ~4500 to remove stellar and galaxy contaminants in the sample to a very high level, based on the 7-band photometry. We discuss the distributions of redshift, luminosity, and reddening of the 19100 QSOs (~96%) that we estimate to be present in the final sample of 19812 point sources.
