- ID:
- ivo://CDS.VizieR/J/PAZh/33/403
- Title:
- Globular clusters as gravitational lenses
- Short Name:
- J/PAZh/33/403
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on the SDSS catalog, we have found new close quasar-galaxy pairs. We analyze the radial distribution of quasars from pairs around galaxies of different types. We show that the quasars from pairs follow the density profile of halo globular clusters. This is new observational evidence that the quasars projected onto the halos of galaxies are magnified by gravitational lensing by halo globular clusters.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/544/A25
- Title:
- GPS radio sources multifrequency study
- Short Name:
- J/A+A/544/A25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Gigahertz peaked spectrum (GPS) radio sources are a class of extragalactic radio sources characterized by a spectral peak in the gigahertz domain. They are a mixed class of quasars and galaxies. A large proportion of the sources studied in the literature have only few data points in the radio domain, and the determination of variability and shape of the simultaneous spectra is inadequate. Sources currently included in the GPS source lists are very heterogeneous. We present the observational results from 12 observing campaigns (carried out between 2006 and 2010) at the RATAN-600 radio telescope to obtain the simultaneous radio spectra, which is valuable and necessary to derive genuine GPS sources from flat-spectrum radio sources caught in a flaring state when their spectra are temporarily inverted. The sample contains both quasar- and galaxy-type GPS (122 sources) identified in the literature.
- ID:
- ivo://CDS.VizieR/J/AJ/131/49
- Title:
- Gravitational lenses among z>=4.0 quasars
- Short Name:
- J/AJ/131/49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on i-band snapshot observations of 157 Sloan Digital Sky Survey quasars at 4.0<z<5.4 using the Advanced Camera for Surveys on the Hubble Space Telescope (HST) to search for evidence of gravitational lensing of these sources.
- ID:
- ivo://CDS.VizieR/J/ApJ/409/28
- Title:
- Gravitationally Lensed Quasars
- Short Name:
- J/ApJ/409/28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Snapshot Survey was a search for cases of gravitational lensing among intrinsically-luminous, high-redshift quasars using the Hubble Space Telescope (HST) Planetary Camera (PC). The accompanying ASCII tables summarize the results of the survey.
- ID:
- ivo://CDS.VizieR/J/MNRAS/458/2
- Title:
- Gravitationally lensed quasars
- Short Name:
- J/MNRAS/458/2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of an imaging observation campaign conducted with the Subaru Telescope adaptive optics system (IRCS+AO188) on 28 gravitationally lensed quasars and candidates (23 doubles, 1 quad, 1 possible triple, and 3 candidates) from the SDSS Quasar Lens Search. We develop a novel modelling technique that fits analytical and hybrid point spread functions (PSFs), while simultaneously measuring the relative astrometry, photometry, as well as the lens galaxy morphology. We account for systematics by simulating the observed systems using separately observed PSF stars. The measured relative astrometry is comparable with that typically achieved with the Hubble Space Telescope, even after marginalizing over the PSF uncertainty. We model for the first time the quasar host galaxies in five systems, without a priori knowledge of the PSF, and show that their luminosities follow the known correlation with the mass of the supermassive black hole. For each system, we obtain mass models far more accurate than those previously published from low-resolution data, and we show that in our sample of lensing galaxies the observed light profile is more elliptical than the mass, for ellipticity >~0.25. We also identify eight doubles for which the sources of external and internal shear are more reliably separated, and should therefore be prioritized in monitoring campaigns aimed at measuring time delays in order to infer the Hubble constant.
- ID:
- ivo://CDS.VizieR/J/ApJ/862/123
- Title:
- griz light curves of 15 DES quasars
- Short Name:
- J/ApJ/862/123
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present accretion disk size measurements for 15 luminous quasars at 0.7<=z<=1.9 derived from griz light curves from the Dark Energy Survey. We measure the disk sizes with continuum reverberation mapping using two methods, both of which are derived from the expectation that accretion disks have a radial temperature gradient and the continuum emission at a given radius is well described by a single blackbody. In the first method we measure the relative lags between the multiband light curves, which provides the relative time lag between shorter and longer wavelength variations. From this, we are only able to constrain upper limits on disk sizes, as many are consistent with no lag the 2{sigma} level. The second method fits the model parameters for the canonical thin disk directly rather than solving for the individual time lags between the light curves. Our measurements demonstrate good agreement with the sizes predicted by this model for accretion rates between 0.3 and 1 times the Eddington rate. Given our large uncertainties, our measurements are also consistent with disk size measurements from gravitational microlensing studies of strongly lensed quasars, as well as other photometric reverberation mapping results, that find disk sizes that are a factor of a few (~3) larger than predictions.
297. Group of quasars
- ID:
- ivo://CDS.VizieR/J/MNRAS/249/218
- Title:
- Group of quasars
- Short Name:
- J/MNRAS/249/218
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have found evidence for a large, elongated group of at least ten quasars with largest dimension ~100-200h-1Mpc at z~1.3, in the direction of ESO/SERC field 927, which has the field centre (1950) 10h40m00s, 05deg00'00". There are probably further members that have not yet been observed. The morphology of the group seems to be like a clump, but there might be some sub-grouping on scales ~20h-1Mpc. The group is similar in size and number of quasars to that found by Crampton, Cowley & Hartwick (1989). The fact that two such groups are now known is evidence that the distribution of quasars is not so simple as was previously thought: at large scales (>10h-1Mpc) the majority of quasars may be distributed uniformly and at random, but rare, large groups also occur. The groups may be large physical structures, but a strong association with the large structures of galaxies seems doubtful.
- ID:
- ivo://CDS.VizieR/J/A+A/513/A21
- Title:
- GRS 1915+105 timing analysis
- Short Name:
- J/A+A/513/A21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- GRS 1915+105 was observed by BeppoSAX for about 10 days in October 2000. For about 80% of the time, the source was in the variability class rho, characterised by a series of recurrent bursts. We describe the results of the timing analysis performed on the MECS (1.6-10keV) and PDS (15-100keV) data. The X-ray count rate from GRS 1915+105 showed an increasing trend with different characteristics in the various energy bands: in the bands (1.6-3keV) and (15-100keV), it was nearly stable in the first part of the pointing and increased in a rather short time by about 20%, while in the energy range (3-10keV) the increase had a smoother trend.
- ID:
- ivo://CDS.VizieR/J/A+A/570/A96
- Title:
- GTC spectra of z~2.3 quasars
- Short Name:
- J/A+A/570/A96
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The advent of 8-10m class telescopes for the first time makes it possible to compare in detail quasars with similar luminosity and very different redshifts. We conducted a search for z-dependent gradients in line-emission diagnostics and derived physical properties by comparing, in a narrow bolometric luminosity range (logL~46.1+/-0.4erg/s), some of the most luminous local z<0.6 quasars with some of the lowest luminosity sources yet found at redshift z=2.1-2.5. Moderate signal-to-noise ratio spectra for 22 high-redshift sources were obtained with the 10.4m Gran Telescopio Canarias (GTC), for which the HST (largely the Faint Object Spectrograph) archive provides a low-redshift control sample. We compared the spectra in the context of the 4D Eigenvector 1 formalism, meaning that we divided both source samples into highly accreting population A and population B sources accreting at a lower rate. CIV {lambda}1549, the strongest and most reliable diagnostic line, shows very similar properties at both redshifts, which confirms the CIV {lambda}1549 profile differences at high redshift between populations A and B, which are well established in local quasars. The CIV {lambda}1549 blueshift that appears quasi-ubiquitous in higher L sources is found in only half (population A) of the quasars observed in the two samples. A CIV {lambda}1549 evolutionary Baldwin effect is certainly disfavored. We find evidence for lower metallicity in the GTC sample that may point toward a gradient with z. No evidence for a gradient in black hole mass or Eddington ratio is found. Spectroscopic differences established at low z are also present in much higher redshift quasars. Our results on the CIV {lambda}1549 blueshift suggest that it depends both on source luminosity and Eddington ratio. Given that our samples involve sources with very similar luminosity, the evidence for a systematic metallicity decrease, if real, points toward an evolutionary effect. Our samples are not large enough to effectively constrain possible changes of black hole mass or Eddington ratio with redshift. The two samples appear representative of a slowly evolving quasar population that is most likely present at all redshifts.
- ID:
- ivo://CDS.VizieR/J/ApJS/234/16
- Title:
- H{alpha} & H{beta} spectral regions of low-z QSOs
- Short Name:
- J/ApJS/234/16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the quasars with z_em_<0.9 from the Baryon Oscillation Spectroscopic Survey, we measure the spectral characteristics, including continuum and emission lines, around the H{beta} and H{alpha} spectral regions, which are lacking in Quasar Data Release 12 (DR12Q). We estimate the virial black hole mass from broad H{alpha} and/or H{beta}, and infer quasar redshifts from [OIII]{lambda}5007 emission lines. All the measurements and derived quantities are publicly available. A comparison between [OIII]{lambda}5007 redshifts and the visual inspection redshifts included in DR12Q indicates that the visual inspection redshifts are robust. We find that the full widths at half maximum of the broad H{alpha} are consistent with those of the broad H{beta}, while both the equivalent widths and line luminosities of the broad H{alpha} are obviously larger than the corresponding quantities of the broad H{beta}. We also find that there is an obviously systematic offset between the H{beta} and H{alpha} based mass if they are inferred from the empirical relationships in the literature. Using our large quasar sample, we have improved the H{beta} and H{alpha} based mass estimators by minimizing the difference between the H{beta}- and H{alpha}-based masses. For the black hole mass estimator (Equation (1)), we find that the coefficients (a,b)=(7.00,0.50) for H{alpha} and (a,b)=(6.96,0.50) for H{beta} are the best choices.
