Related papers: Quasar identifications from the slitless spectra: …

We obtained SDSS spectra for a set of 37 radio-quiet quasars (RQQSOs) that had been previously examined for rapid small scale optical variations, or microvariability. Their H-beta and Mg II emission lines were carefully fit to determine…

The census of obscured quasar populations is incomplete, and remains a major unsolved problem, especially at higher redshifts, where we expect a greater density of galaxy formation and quasar activity. We present Gemini GNIRS near-infrared…

(Abridged) We report on the X-ray and multiwavelength properties of 11 radio-quiet quasars with weak or no emission lines identified by the Sloan Digital Sky Survey (SDSS) with redshift z=0.4-2.5. The distribution of relative X-ray…

Identifications of quasars at intermediate redshifts (2.2<z<3.5) are inefficient in most previous quasar surveys as their optical colors are similar to those of stars. The near-IR K-band excess technique has been suggested to overcome this…

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,…

We develop a method for separating quasars from other variable point sources using SDSS Stripe 82 light curve data for ~10,000 variable objects. To statistically describe quasar variability, we use a damped random walk model parametrized by…

The KPNO International Spectroscopic Survey (KISS) is a new objective-prism survey for extragalactic emission-line objects. It combines many of the features of previous slitless spectroscopic surveys with the advantages of modern CCD…

The main goal of this study was to determine the effects on equivalent widths (EWs) of some spectral lines produced in the quasars by the presence of surrounding galaxies. To carry this out, a sample of 4663 quasars (QSOs) in the redshift…

Upcoming surveys such as Euclid, the Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST) and the Nancy Grace Roman Telescope (Roman) will detect hundreds of high-redshift (z > 7) quasars, but distinguishing them from the…

The largest K-band flux-limited sample of luminous quasars to date has been constructed from the UKIDSS Large Area Survey Early Data Release, covering an effective area of 12.8 deg^2. Exploiting the K-band excess of all quasars with respect…

We present Chandra observations of 2106 radio-quiet quasars in the redshift range 1.7<z<2.7 from the Sloan Digital Sky Survey (SDSS), through data release fourteen (DR14), that do not contain broad absorption lines (BAL) in their rest-frame…

The KPNO International Spectroscopic Survey (KISS) is an objective-prism survey for extragalactic emission-line objects. It combines many of the features of previous slitless spectroscopic surveys with the advantages of modern CCD…

We present 3D-HST, a near-infrared spectroscopic Treasury program with the Hubble Space Telescope for studying the processes that shape galaxies in the distant Universe. 3D-HST provides rest-frame optical spectra for a sample of ~7000…

Nearly one-third of the gamma-ray sources detected by Fermi are still unidentified, despite significant recent progress in this effort. On the other hand, all the gamma-ray extragalactic sources associated in the second Fermi-LAT catalog…

We searched for the presence of extended emission-line regions (EELRs) around low-redshift QSOs. We observed a sample of 20 mainly radio-quiet low-redshift quasars (z<0.3) by means of integral field spectroscopy. After decomposing the…

The Grism Lens-Amplified Survey from Space (GLASS) is a Hubble Space Telescope (HST) Large Program, which will obtain 140 orbits of grism spectroscopy of the core and infall regions of 10 galaxy clusters, selected to be among the very best…

The Star Formation Across Cosmic Time (SFACT) survey is a new narrowband survey designed to detect emission-line galaxies (ELGs) and quasi-stellar objects (QSOs) over a wide range of redshifts in discrete redshift windows. The survey…

We exploit the spectral archive of the Sloan Digital Sky Survey (SDSS) Data Release 7 to select unusual quasar spectra. The selection method is based on a combination of the power of self-organising maps and the visual inspection of a huge…

We present a new measurement of the space density of high redshift (3.0<z<4.5), X-ray selected QSOs obtained by exploiting the deep and uniform multiwavelength coverage of the COSMOS survey. We have assembled a statistically large (40…

We identify 885,503 type 1 quasar candidates to i<22 using the combination of optical and mid-IR photometry. Optical photometry is taken from the Sloan Digital Sky Survey-III: Baryon Oscillation Spectroscopic Survey (SDSS-III/BOSS), while…