Results 81 to 90 of about 116,814 (325)
Understanding extreme quasar optical variability with CRTS – II. Changing-state quasars [PDF]
Monthly notices of the Royal Astronomical Society, 2019 We present the results of a systematic search for quasars in the Catalina Real-time Transient Survey exhibiting both strong photometric variability and spectroscopic variability over a decadal baseline. We identify 111 sources with specific patterns of
M. Graham +10 more
semanticscholar +1 more source
Quasars Probing Quasars. II. The Anisotropic Clustering of Optically Thick Absorbers around Quasars [PDF]
The Astrophysical Journal, 2007 With close pairs of quasars at different redshifts, a background quasar sightline can be used to study a foreground quasar's environment in absorption. We used a sample of 17 Lyman limit systems with column density N_HI > 10^19 cm^-2 selected from 149 projected quasar pair sightlines, to investigate the clustering pattern of optically thick ...
Joseph F. Hennawi, Jason X. Prochaska
openaire +3 more sources
The Nature of Radio-Intermediate Quasars: What is Radio-Loud and what is Radio-Quiet? [PDF]
, 1996 We have performed quasi-simultaneous radio flux density measurements at 2.7 and 10 GHz for all PG quasars with radio flux densities between 4-200 mJy. We find that a large fraction of these sources are variable, flat-spectrum quasars. This brings the total fraction of flat-spectrum quasars with a ratio between radio and optical flux of R>10 - a value ...
arxiv +1 more source
Baryon acoustic oscillations in the Lyα forest of BOSS DR11 quasars [PDF]
, 2014 We report a detection of the baryon acoustic oscillation (BAO) feature in the flux-correlation function of the Ly forest of high-redshift quasars with a statistical significance of five standard deviations.
T. Delubac +37 more
semanticscholar +1 more source
Spectroscopic Target Selection in the Sloan Digital Sky Survey: The Quasar Sample [PDF]
, 2002 We describe the algorithm for selecting quasar candidates for optical spectroscopy in the Sloan Digital Sky Survey. Quasar candidates are selected via their non-stellar colors in "ugriz" broad-band photometry, and by matching unresolved sources to the ...
Adam Boucher +24 more
core +2 more sources
Exploiting the IRT-THESEUS Capability to Observe Lensed Quasars
Galaxies, 2021 THESEUS is an ESA space based project, which aims to explore the early universe by unveiling a complete census of Gamma-ray Burst (GRB) population in the first billion years.
Lindita Hamolli +3 more
doaj +1 more source
Relations Between Environments of Quasars and Galaxy Formation [PDF]
Publ.Astron.Soc.Jpn. 55 (2003) 134, 2002 We investigate the environments of quasars such as number distribution of galaxies using a semi-analytic model which includes both galaxy and quasar formations based on the hierarchical clustering scenario. We assume that a supermassive black hole is fueled by accretion of cold gas and that it is a source of quasar activity during a major merger of the
arxiv +1 more source
, 2008 We investigate the $\mbh- \sigma_*$ relation for radio-loud quasars with redshift ...
Abazajian K +55 more
core +1 more source
Four quasars above redshift 6 discovered by the Canada-France High-z Quasar Survey [PDF]
, 2007 The Canada-France High-z Quasar Survey (CFHQS) is an optical survey designed to locate quasars during the epoch of reionization. In this paper we present the discovery of the first four CFHQS quasars at redshift greater than 6, including the most distant
Alain Omont +22 more
core +5 more sources
Imprints of the super-Eddington accretion on the quasar clustering [PDF]
, 2017 Super-Eddington mass accretion has been suggested as an efficient mechanism to grow supermassive black holes (SMBHs). We investigate the imprint left by the radiative efficiency of the super-Eddington accretion process on the clustering of quasars using a new semi-analytic model of galaxy and quasar formation based on large-volume cosmological $N$-body
arxiv +1 more source