- ID:
- ivo://CDS.VizieR/J/MNRAS/440/799
- Title:
- Low Ionization BALQSOs MgII and AlIII variability
- Short Name:
- J/MNRAS/440/799
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of our time variability studies of MgII and AlIII absorption lines in a sample of 22 Low Ionization Broad Absorption Line QSOs (LoBAL QSOs) at 0.2<=z_em_<=2.1 using the 2-m telescope at IUCAA Girawali Observatory over a time-scale of 10d to 7.69years in the QSO's rest frame. Spectra are analysed in conjunction with photometric light curves from Catalina Real-Time Transient Survey. Long time-scale (i.e. >=1-year) absorption line variability is seen in eight cases (36 per cent systems) while only four of them (i.e. 18 per cent systems) show variability over short time-scales (i.e. <1-year). We notice a tendency of highly variable LoBAL QSOs to have high ejection velocity, low equivalent width and low redshift. The detection rate of variability in LoBAL QSOs showing Fe fine-structure lines (FeLoBAL QSOs) is less than that seen in non-Fe LoBAL QSOs. Absorption line variability is more frequently detected in QSOs having continuum dominated by Fe emission lines compared to rest of the QSOs. Confirming these trends with a bigger sample will give vital clues for understanding the physical distinction between different BAL QSO sub-classes. We correlate the absorption line variability with various parameters derived from continuum light curves and find no clear correlation between continuum flux and absorption line variabilities. However, sources with large absorption line variability also show large variability in their light curves. We also see appearance/disappearance of absorption components in two cases and clear indications for profile variations in four cases. The observed variability can be best explained by a combination of process driven by continuum variations and clouds transiting across the line of sight.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/561/A140
- Title:
- Low-luminosity type-1 QSO sample
- Short Name:
- J/A+A/561/A140
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recognizing the properties of the host galaxies of quasi-stellar objects (QSOs) is essential to understand the suspected coevolution of central supermassive black holes (BHs) and their host galaxies. We selected a subsample of the Hamburg/ESO survey for bright UV-excess QSOs, containing only the 99 nearest QSOs with redshift z<=0.06, that are close enough to allow detailed structural analysis. From this "low-luminosity type-1 QSO sample", we observed 20 galaxies and performed aperture photometry and bulge-disk-bar-AGN-decomposition with BUDDA on near-infrared J, H, K band images. From the photometric decomposition of these 20 objects and visual inspection of images of another 26, we find that ~50% of the hosts are disk galaxies and most of them (86%) are barred. Stellar masses, calculated from parametric models based on inactive galaxy colors, range from 2x10^9^M_{sun}_ to 2x10^11^M_{sun}_. Black hole masses measured from single epoch spectroscopy range from 1x10^6^M_{sun}_ to 5x10^8^M_{sun}_. In comparison to higher luminosity QSO samples, LLQSOs tend to have lower stellar and BH masses. Also, in the effective radius vs. mean surface-brightness projection of the fundamental plane, they lie in the transition area between luminous QSOs and "normal" galaxies. This can be seen as further evidence that they can be pictured as a "bridge" between the local Seyfert population and luminous QSOs at higher redshift. Eleven low-luminosity QSOs for which we have reliable morphological decompositions and BH mass estimations lie below the published BH mass vs. bulge luminosity relations for inactive galaxies. This could be partially explained by bulges of active galaxies containing much younger stellar populations than bulges of inactive galaxies. Also, one could suspect that their BHs are undermassive. This might hint at the growth of the host spheroid to precede that of the BH.
- ID:
- ivo://CDS.VizieR/J/ApJ/633/630
- Title:
- Low-mass stars found in CFHTLS
- Short Name:
- J/ApJ/633/630
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present preliminary results of a new quasar survey being undertaken with multicolor optical imaging from the Canada-France-Hawaii Telescope. The current data consist of 3.83deg^2^ of imaging in the i' and z' filters to a 10{sigma} limit of z'<23.35. Near-infrared photometry of 24 candidate 5.7<z<6.4 quasars confirms them all to be low-mass stars, including two T dwarfs and four or five L dwarfs. Photometric estimates of the spectral type of the two T dwarfs are T3 and T6.
- ID:
- ivo://CDS.VizieR/J/MNRAS/441/1802
- Title:
- Low-redshift QSOs in SDSS Stripe 82
- Short Name:
- J/MNRAS/441/1802
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the environments of low-redshift (z<0.5) quasars based on a large and homogeneous data set from the Stripe 82 region of the Sloan Digital Sky Survey (SDSS). We have compared the <1Mpc scale environments of 302 quasars that were resolved in our recent study to those of 288 inactive galaxies with closely matched redshifts. Crucially, the luminosities of the inactive galaxies and the quasar host galaxies are also closely matched, unlike in most previous studies. The environmental overdensities were studied by measuring the number density of galaxies within a projected distance of 200kpc to 1Mpc. The galaxy number density of the quasar environments is comparable to that of the inactive galaxies with similar luminosities, both classes of objects showing significant excess compared to the background galaxy density for distances <400kpc. There is no significant dependence of the galaxy number density on redshift, quasar or host galaxy luminosity, black hole mass or radio loudness. This suggests that the fuelling and triggering of the nuclear activity is only weakly dependent on the local environment of quasars, and the quasar phase may be a short-lived common phase in the life cycle of all massive galaxies.
- ID:
- ivo://CDS.VizieR/J/MNRAS/440/476
- Title:
- Low-redshift quasars in SDSS Stripe 82
- Short Name:
- J/MNRAS/440/476
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a photometrical and morphological study of the properties of low-redshift (z<0.5) quasars based on a large and homogeneous data set of objects derived from the Sloan Digital Sky Survey Data Release 7. This study over number by a factor of ~5 any other previous study of quasi-stellar object (QSO) host galaxies at low redshift undertaken either on ground or on space surveys. We used ~400 quasars that were imaged in the SDSS Stripe 82 that is up to 2mag deeper than standard Sloan images. For these quasars we undertake a study of the host galaxies and of their environments. In this paper we report the results for the quasar hosts. We are able to detect the host galaxy for more than 3/4 of the whole data set and characterize the properties of their hosts. We found that QSO hosts are dominated by luminous galaxies of absolute magnitude M*-3<M(R)<M*. For the unresolved objects we computed an upper limit to the host luminosity. For each well-resolved quasar we are also able to characterize the morphology of the host galaxy that turn out to be more complex than what found in previous studies. QSOs are hosted in a variety of galaxies from pure ellipticals to complex/composite morphologies that combine spheroids, disc, lens and halo. The black hole (BH) mass of the quasar, estimated from the spectral properties of the nuclei, is poorly correlated with the total luminosity of the host galaxy. However, taking into account only the bulge component we found a significant correlation between the BH mass and the bulge luminosity of the host.
436. Low-z BQS Quasars
- ID:
- ivo://CDS.VizieR/J/MNRAS/263/425
- Title:
- Low-z BQS Quasars
- Short Name:
- J/MNRAS/263/425
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
- ID:
- ivo://CDS.VizieR/I/313
- Title:
- LQRF: Large Quasar Reference Frame
- Short Name:
- I/313
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The LQRF (Large Quasar Reference Frame) was built with the care of avoiding wrong matches of its constituents quasars, of homogenizing the astrometry from the different catalogs and lists from which the constituent quasars are gathered, and of attaining the milli-arcsec global alignment to the ICRF (International Celestial Reference Frame), as well as typical individual source position accuracies even to better than 100 milli-arcsec. Starting from the updated and presumably complete LQAC (Large Quasar Astrometric Catalog) list of QSOs, initial optical positions for those quasars are found in the USNO B1.0 and GSC2.3 catalogs, and from the SDSS Data Release 5. The initial positions are next placed onto UCAC2 based reference frames, following by an alignment to the ICRF, as well as of the most precise sources from the VLBA calibrator list and from the VLA calibrator list - when reliable optical counterparts exist. Finally the LQRF axes are inspected through spherical harmonics, contemplating right ascension, declination and magnitude terms.
- ID:
- ivo://CDS.VizieR/J/ApJ/746/169
- Title:
- Luminosity function of broad-line quasars
- Short Name:
- J/ApJ/746/169
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We jointly constrain the luminosity function (LF) and black hole mass function (BHMF) of broad-line quasars with forward Bayesian modeling in the quasar mass-luminosity plane, based on a homogeneous sample of ~58000 Sloan Digital Sky Survey (SDSS) Data Release 7 quasars at z~0.3-5. We take into account the selection effect of the sample flux limit; more importantly, we deal with the statistical scatter between true BH masses and FWHM-based single-epoch virial mass estimates, as well as potential luminosity-dependent biases of these mass estimates. The LF is tightly constrained in the regime sampled by SDSS and makes reasonable predictions when extrapolated to ~3 mag fainter. Downsizing is seen in the model LF. On the other hand, we find it difficult to constrain the BHMF to within a factor of a few at z >~ 0.7 (with Mg II and C IV-based virial BH masses). This is mainly driven by the unknown luminosity-dependent bias of these mass estimators and its degeneracy with other model parameters, and secondly driven by the fact that SDSS quasars only sample the tip of the active BH population at high redshift. Nevertheless, the most likely models favor a positive luminosity-dependent bias for Mg II and possibly for C IV, such that at fixed true BH mass, objects with higher-than-average luminosities have overestimated FWHM-based virial masses. There is tentative evidence that downsizing also manifests itself in the active BHMF, and the BH mass density in broad-line quasars contributes an insignificant amount to the total BH mass density at all times. Within our model uncertainties, we do not find a strong BH mass dependence of the mean Eddington ratio, but there is evidence that the mean Eddington ratio (at fixed BH mass) increases with redshift.
- ID:
- ivo://CDS.VizieR/J/ApJ/764/45
- Title:
- Luminosity function of broad-line quasars. II.
- Short Name:
- J/ApJ/764/45
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We employ a flexible Bayesian technique to estimate the black hole (BH) mass and Eddington ratio functions for Type 1 (i.e., broad line) quasars from a uniformly selected data set of ~58000 quasars from the Sloan Digital Sky Survey (SDSS) DR7. We find that the SDSS becomes significantly incomplete at M_BH_<~3x10^8^M_{sun}_ or L/L_Edd_<~0.07, and that the number densities of Type 1 quasars continue to increase down to these limits. Both the mass and Eddington ratio functions show evidence of downsizing, with the most massive and highest Eddington ratio BHs experiencing Type 1 quasar phases first, although the Eddington ratio number densities are flat at z<2. We estimate the maximum Eddington ratio of Type 1 quasars in the observable universe to be L/L_Edd_~3. Consistent with our results in Shen & Kelly (Paper I, Cat. J/ApJ/746/169), we do not find statistical evidence for a so-called sub-Eddington boundary in the mass-luminosity plane of broad-line quasars, and demonstrate that such an apparent boundary in the observed distribution can be caused by selection effect and errors in virial BH mass estimates. Based on the typical Eddington ratio in a given mass bin, we estimate growth times for the BHs in Type 1 quasars and find that they are comparable to or longer than the age of the universe, implying an earlier phase of accelerated (i.e., with higher Eddington ratios) and possibly obscured growth. The large masses probed by our sample imply that most of our BHs reside in what are locally early-type galaxies, and we interpret our results within the context of models of self-regulated BH growth.
- ID:
- ivo://CDS.VizieR/J/ApJ/779/104
- Title:
- Luminous dust-poor SDSS QSOs at z<4.5
- Short Name:
- J/ApJ/779/104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We identify and characterize a population of luminous, dust-poor quasars at 0<z<5 that is photometrically similar to objects previously found at z>6. This class of active galactic nuclei is known to show little IR emission from dusty structure, but it is poorly understood in terms of number evolution and dependence on physical quantities. To better understand the properties of these quasars, we compile a rest-frame UV to IR library of 41000 optically selected type 1 quasars with L_bol_>10^45.7^erg/s. After fitting the broadband spectral energy distributions (SEDs) with accretion disk and dust components, we find 0.6% of our sample to be hot dust-poor, with rest-frame 2.3{mu}m to 0.51{mu}m flux density ratios of -0.5dex or less. The dust-poor SEDs are blue in the UV-optical and weak in the mid-IR, such that their accretion disks are less obscured and the hot dust emission traces that of warm dust down to the dust-poor regime. At a given bolometric luminosity, dust-poor quasars are lower in black hole mass and higher in Eddington ratio than general luminous quasars, suggesting that they are in a rapidly growing evolutionary state in which the dust-poor phase appears as a short or rare phenomenon. The dust-poor fraction increases with redshift, and possible implications for their evolution are discussed.
