Results 41 to 50 of about 86,681 (283)
Shedding New Light on Weak Emission-line Quasars in the C iv–Hβ Parameter Space
The Astrophysical Journal, 2023 Weak emission-line quasars (WLQs) are a subset of type 1 quasars that exhibit extremely weak Ly α + N v λ 1240 and/or C iv λ 1549 emission lines. We investigate the relationship between emission-line properties and accretion rate for a sample of 230 ...
Trung Ha +22 more
doaj +1 more source
Why radio quiet quasars are preferred over radio loud quasars regardless of environment and redshift [PDF]
The Astrophysical Journal 2020, 2020 Evidence has accumulated suggesting the clustering of radio loud quasars is greater than for radio quiet quasars. We interpret these results in a context in which the fraction of radio loud quasar formation is less than or equal to that for radio quiet quasars for all environments and redshift.
arxiv +1 more source
Quasar-galaxy associations [PDF]
Monthly Notices of the Royal Astronomical Society, 1995 uuencoded Postscript file (including figures and tables), SUSSEX-AST 94/8 ...
Thomas, P. A. +2 more
openaire +6 more sources
Gaia Space Mission and Quasars
Frontiers in Astronomy and Space Sciences, 2017 Quasars are often considered to be point-like objects. This is largely true and allows for an excellent alignment of the optical positional reference frame of the ongoing ESA mission Gaia with the International Celestial Reference Frame.
Tomaž Zwitter
doaj +1 more source
The Astrophysical Journal, 2023 We explore reprocessing models for a sample of 17 hypervariable quasars, taken from the Sloan Digital Sky Survey Reverberation Mapping project, which all show coordinated optical luminosity hypervariability with amplitudes of factors ≳2 between 2014 and ...
Tatsuya Akiba +7 more
doaj +1 more source
Science, 1986 In the quarter century since the first optical identification of a "radio star" (3C 48), astronomers have come to general agreement that the underlying quasar energy source is accretion onto a massive black hole. There is much less agreement on the detailed physics of the processes by which this energy is converted to the forms observed, but this has ...
Trimble, Virginia, Woltjer, Lodewijk
openaire +4 more sources
The quasar luminosity function at $z\sim5$ via deep learning and Bayesian information criterion [PDF]
, 2022 Understanding the faint end of quasar luminosity function at a high redshift is important since the number density of faint quasars is a critical element in constraining ultraviolet (UV) photon budgets for ionizing the intergalactic medium (IGM) in the early universe.
arxiv +1 more source
Determining the fraction of reddened quasars in COSMOS with multiple selection techniques from X-ray to radio wavelengths [PDF]
, 2016 The sub-population of quasars reddened by intrinsic or intervening clouds of dust are known to be underrepresented in optical quasar surveys. By defining a complete parent sample of the brightest and spatially unresolved quasars in the COSMOS field, we ...
Fynbo, J. P. U. +10 more
core +1 more source
The Sloan Digital Sky Survey Quasar Lens Search. II. Statistical lens sample from the third data release [PDF]
, 2007 We report the first results of our systematic search for strongly lensed quasars using the spectroscopically confirmed quasars in the Sloan Digital Sky Survey (SDSS).
Anderson, Scott F. +33 more
core +3 more sources
Proceedings of the International Astronomical Union, 2014 AbstractAlthough the extragalactic nature of 3C 48 and other quasi stellar radio sources was discussed as early as 1960 by John Bolton and others, it was rejected largely because of preconceived ideas about what appeared to be unrealistically high radio and optical luminosities.
openaire +3 more sources