Related papers: The Quasar Mass-Luminosity Plane III: Smaller Erro…

The ensemble variability properties of nearly 23,000 quasars are studied using the Palomar-QUEST Survey. The survey has covered 15,000 square degrees multiple times over 3.5 years using 7 optical filters, and has been calibrated…

We present the results of a multi-colour (VIZ) survey for low luminosity (M_B<-23.5) quasars with z~5 using the 12K CCD mosaic camera on CFHT. The survey covers 1.8deg^2 to a limiting magnitude of m_z=22.5(Vega), about two magnitudes…

We perform a systematic search for high-redshift ($z >$ 1.5) extreme variability quasars (EVQs) using repeat spectra from the Sixteenth Data Release of Sloan Digital Sky Survey, which provides a baseline spanning up to $\sim$18 yrs in the…

We present a strong lensing analysis of the galaxy cluster SDSS J1029+2623 at $z=0.588$, one of the few currently known lens clusters with multiple images of a background ($z=2.1992$) quasar with a measured time delay. We use archival…

{}From three quasar samples with a total of 1038 objects in the redshift range $1.0 \div 2.2$ we measure the variance $\sigma^2$ of counts in cells of volume $V_u$. By a maximum likelihood analysis applied separately on these samples we…

We present a correlation between the 2-10 keV spectral slope Gamma and the Eddington ratio L/L_{EDD} in a sample of ~400 Sloan Digital Sky Survey quasars with available hard X-ray spectra from XMM-Newton serendipitous observations. We find…

Recently, Carnall et al. discovered two bright high redshift quasars using the combination of the VST ATLAS and WISE surveys. The technique involved using the 3-D colour plane i-z:z-W1:W1-W2 with the WISE W1 (3.4 micron) and W2 (4.5 micron)…

We investigate the properties of the most distant quasars ULASJ134208.10+092838.61 ($z = 7.54$), ULASJ112001.48+064124.3 ($z = 7.08$) and DELSJ003836.10-152723.6 ($z = 7.02$) studying their Optical-UV emission that shows clear evidence of…

The most reliable single-epoch supermassive black hole mass ($M_{\rm BH}$) estimates in quasars are obtained by using the velocity widths of low-ionization emission lines, typically the H$\beta$ $\lambda4861$ line. Unfortunately, this line…

We present deep near-infrared spectroscopy of six quasars at 6.1<z<6.7 with VLT/X-Shooter and Gemini-N/GNIRS. Our objects, originally discovered through a wide-field optical survey with the Hyper Suprime-Cam (HSC) Subaru Strategic Program…

We present the ensemble variability analysis results of quasars using the Dark Energy Camera Legacy Survey (DECaLS) and the Sloan Digital Sky Survey (SDSS) quasar catalogs. Our dataset includes 119,305 quasars with redshifts up to 4.89.…

We study the dependence of the number density and properties of quasars on the background galaxy density using the currently largest spectroscopic datasets of quasars and galaxies. We construct a galaxy number density field smoothed over…

Over the last few years, the Sloan Digital Sky Survey (SDSS) has discovered several hundred quasars with redshift between 4.0 and 6.4. Including the effects of magnification bias, one expects a priori that an appreciable fraction of these…

We use the Sloan Digital Sky Survey (SDSS) Quasar Data Release 12 (DR12Q), containing nearly 300,000 AGNs, to calculate the monochromatic luminosities at 5100\AA, 3000\AA, and 1350\AA, derived from the broad-band extinction-corrected SDSS…

We present the discovery of five quasars at z~6 selected from 260 deg^2 of the Sloan Digital Sky Survey (SDSS) southern survey, a deep imaging survey obtained by repeatedly scanning a stripe along the Celestial Equator. The five quasars…

We present the discovery of a new quadruply lensed quasar. The lens system, SDSS J1330+1810 at z_s=1.393, was identified as a lens candidate from the spectroscopic sample of the Sloan Digital Sky Survey. Optical and near-infrared images…

We report the discovery of a bright (g = 14.5 mag (AB), K = 11.9 mag (Vega)) quasar at redshift z = 0.83 -- the optically brightest (unbeamed) quasar at z > 0.4. SMSS J114447.77-430859.3, at a Galactic latitude of b = +18.1deg, was…

We present the second edition of the Sloan Digital Sky Survey (SDSS) Quasar Catalog. The catalog consists of 16713 objects in the SDSS First Data Release (DR1) that have luminosities larger than M_i=-22 (H_0=70 km/s, Omega_M=0.3,…

Most of the successful physical theories rely on the constancy of few fundamental quantities (such as the speed of light, $c$, the fine-structure constant, \alpha, the proton to electron mass ratio, \mu, etc), and constraining the possible…

Molecular transitions recently discovered at redshift z_abs=2.059 toward the bright background quasar J2123-0050 are analysed to limit cosmological variation in the proton-to-electron mass ratio, mu=m_p/m_e. Observed with the Keck…