Results 11 to 20 of about 94,086 (264)
Do Quasars Lens Quasars? [PDF]
The Astrophysical Journal, 1996 If the unexpectedly high frequency of quasar pairs with very different component redshifts is due to the lensing of a population of background quasars by the foreground quasar, typical lens masses must be $\sim10^{12}M_{\sun}$ and the sum of all such ...
Boyle B. J. +6 more
core +4 more sources
Quasars Probing Quasars. X. The Quasar Pair Spectral Database [PDF]
The Astrophysical Journal Supplement Series, 2018 Abstract The rare close projection of two quasars on the sky provides the opportunity to study the host galaxy environment of a foreground quasar in absorption against the continuum emission of a background quasar. For over a decade the “Quasars probing quasars” series has utilized this technique to further the understanding of galaxy ...
Joseph R. Findlay +10 more
openaire +6 more sources
The Astrophysical Journal Supplement Series, 2023 We report the fourth installment in the series of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) quasar survey, which includes quasars observed between 2017 September and 2021 June.
Jun-Jie Jin +12 more
doaj +1 more source
A hidden population of high-redshift double quasars unveiled by astrometry [PDF]
Nature Astronomy, 2021 Galaxy mergers occur frequently in the early Universe1 and bring multiple supermassive black holes (SMBHs) into the nucleus, where they may eventually coalesce.
Yue Shen +8 more
semanticscholar +1 more source
Quasars Probing Quasars. I. Optically Thick Absorbers near Luminous Quasars [PDF]
The Astrophysical Journal, 2006 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 search 149 moderate resolution background quasar spectra, from Gemini, Keck, the MMT, and the SDSS to survey Lyman Limit Systems (LLSs) and Damped Ly-alpha systems (DLAs) in the vicinity of 1.8 < ...
Hennawi, Joseph F. +13 more
openaire +2 more sources
Investigating Gravitationally Lensed Quasars Observable by Nancy Grace Roman Space Telescope
Galaxies, 2023 In this work, we investigate the possibility of observing quasars, particularly lensed quasars, by the Nancy Grace Roman Space Telescope (Roman).
Lindita Hamolli +3 more
doaj +1 more source
A Test of the Cosmological Principle with Quasars [PDF]
, 2020 We study the large-scale anisotropy of the universe by measuring the dipole in the angular distribution of a flux-limited, all-sky sample of 1.36 million quasars observed by the Wide-field Infrared Survey Explorer (WISE).
N. Secrest +5 more
semanticscholar +1 more source
Quasars as standard candles [PDF]
Astronomy & Astrophysics, 2020 We present a new catalogue of ∼2400 optically selected quasars with spectroscopic redshifts and X-ray observations from either Chandra or XMM–Newton. The sample can be used to investigate the non-linear relation between the ultraviolet (UV) and X-ray ...
E. Lusso +17 more
semanticscholar +1 more source
Reverberation Measurements for 17 Quasars and the Size-Mass-Luminosity Relations in Active Galactic Nuclei [PDF]
, 1999 Correlated variations in the line and continuum emission from active galactic nuclei (AGNs) can be used to determine the size and geometry of the broad emission-line regions (BLRs).
S. Kaspi +5 more
semanticscholar +1 more source
Extreme Quasars as Distance Indicators in Cosmology
Frontiers in Astronomy and Space Sciences, 2020 Quasars accreting matter at very high rates (known as extreme Population A [xA] quasars, possibly associated with super-Eddington accreting massive black holes) may provide a new class of distance indicators covering cosmic epochs from present day up to ...
Deborah Dultzin +10 more
doaj +1 more source