Results 31 to 40 of about 10,418 (177)

GB:1508+5714: a radio-loud quasar with z = 4.30 and the space density of high-redshift radio-loud quasars [PDF]

Monthly Notices of the Royal Astronomical Society, 1995
We report the discovery of a radio loud quasar with a redshift of 4.30. This object, which is the first radio selected quasar with a redshift greater than four, was discovered during an observational investigation into the evolution of the luminosity function of radio loud quasars. Here we describe results based on a sample of ~300, flat spectrum radio
HOOK, IM, MCMAHON, RG, PATNAIK, AR, Browne, Ian, WILKINSON, PN, IRWIN, MJ, HAZARD, C   +6 more
openaire   +3 more sources

Astrometric Apparent Motion of High-redshift Radio Sources

The Astronomical Journal, 2023
Radio-loud quasars at high redshift ( z ≥ 4) are rare objects in the universe and rarely observed with Very Long Baseline Interferometry (VLBI). But some of them have flux density sufficiently high for monitoring of their apparent position.
Oleg Titov, Sándor Frey, Alexey Melnikov, Fengchun Shu, Bo Xia, Javier González, Belén Tercero, Leonid Gurvits, Aletha de Witt, Jamie McCallum, Mikhail Kharinov, Vladimir Zimovsky, Máté Krezinger   +12 more
doaj   +1 more source

QSO environments at intermediate redshifts [PDF]

, 2001
We have made a survey of quasar environments at 0.5 < z < 0.8, using a sample of both radio-loud and radio-quiet quasars matched in B-band luminosity.
Lacy, M., Lilje, P. B., Serjeant, S., Wold, M.   +3 more
core   +2 more sources

Spectroscopic properties of radio-loud and radio-quiet quasars [PDF]

Proceedings of the International Astronomical Union, 2019
AbstractSurveys have shown radio-loud (RL) quasars constitute 10%-15% of the total quasar population and rest are radio-quiet (RQ). However, it is unknown if this radio-loud fraction (RLF) remains consistent among different parameter spaces. This study shows that RLF increases for increasing full width half maximum (FWHM) velocity of the Hβ broad ...
Chakraborty, Avinanda, Bhattacharjee, Anirban   +1 more
openaire   +3 more sources

The radio luminosity, black hole mass and Eddington ratio for quasars from the Sloan Digital Sky Survey [PDF]

, 2008
We investigate the $\mbh- \sigma_*$ relation for radio-loud quasars with redshift ...
Abazajian K, Akritas M G, Bonning E W, Boroson T A, Chen Hu, Dasyra K M, Drory N, Ferrarese L, Gebhardt K, Greene J E, Greene J E, Greene J E, Greene J E, Grupe D, Heckman T M, Ho L C, Ho L C, Kai Huang, Kaspi S, Kaspi S, Komossa S, Komossa S, Lacy M, Laor A, Laor A, Lauer T R, LaValley M P, Liu Y, Nelson C H, Netzer H, Onken C A, Peterson B M, Richards G T, Salviander S, Schneider D P, Shen J-J, Shields J C, Sikora M, Storey P J, Strittmatter P A, Terashima Y, Tremaine S, Treu T, Vanden B, Wang J M, Wang R, Wei-Hao Bian, Whalen D J, Woo J H, Woo J H, Xu C, Yan Xu, Yan-Mei Chen, Yuan F, Zhou H, Zhou H Y   +55 more
core   +1 more source

Symmetry and the Arrow of Time in Theoretical Black Hole Astrophysics

Journal of Gravity, Volume 2015, Issue 1, 2015., 2015
While the basic laws of physics seem time‐reversal invariant, our understanding of the apparent irreversibility of the macroscopic world is well grounded in the notion of entropy. Because astrophysics deals with the largest structures in the Universe, one expects evidence there for the most pronounced entropic arrow of time.
David Garofalo, Cosimo Bambi
wiley   +1 more source

Retrograde versus Prograde Models of Accreting Black Holes

Advances in Astronomy, Volume 2013, Issue 1, 2013., 2013
There is a general consensus that magnetic fields, accretion disks, and rotating black holes are instrumental in the generation of the most powerful sources of energy in the known universe. Nonetheless, because magnetized accretion onto rotating black holes involves both the complications of nonlinear magnetohydrodynamics that currently cannot fully be
David Garofalo, Alberto J. Castro-Tirado
wiley   +1 more source

Radio Loud and Radio Quiet Quasars

, 2016
We discuss 6 GHz JVLA observations covering a volume-limited sample of 178 low redshift ($0.2 < z < 0.3$) optically selected QSOs. Our 176 radio detections fall into two clear categories: (1) About $20$\% are radio-loud QSOs (RLQs) having spectral luminosities $L_6 \gtrsim 10^{\,23.2} \mathrm{~W~Hz}^{-1}$ primarily generated in the active ...
Kellermann, K. I., Condon, J. J., Kimball, A. E., Perley, R. A., Ivezic, Zeljko   +4 more
openaire   +2 more sources

The radio spectral turnover of radio-loud quasars at z > 5 [PDF]

Astronomy & Astrophysics, 2022
We present Karl G. Jansky Very Large Array S- (2–4 GHz), C- (4–8 GHz), and X-band (8–12 GHz) continuum observations toward seven radio-loud quasars at z > 5. This sample has previously been found to exhibit spectral peaks at observed-frame frequencies above ∼1 GHz.
Yali Shao, Jeff Wagg, Ran Wang, Emmanuel Momjian, Chris L. Carilli, Fabian Walter, Dominik A. Riechers, Huib T. Intema, Axel Weiss, Andreas Brunthaler, Karl M. Menten   +10 more
openaire   +4 more sources

The Cosmic History of Black Hole Growth from Deep Multiwavelength Surveys

Advances in Astronomy, Volume 2012, Issue 1, 2012., 2012
Significant progress has been made in the last few years on understanding how supermassive black holes form and grow. In this paper, we begin by reviewing the spectral signatures of active galactic nuclei (AGN) ranging from radio to hard X‐ray wavelengths.
Ezequiel Treister, C. Megan Urry, Francesca Civano   +2 more
wiley   +1 more source