Results 31 to 40 of about 10,384 (186)

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

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

The role of black hole mass in quasar radio activity [PDF]

, 2005
We use a homogeneous sample of about 300, 0.3
Bachev, Becker, Blandford, Blandford, Brotherton, Brotherton, Cavaliere, Cirasuolo, Cirasuolo, Cirasuolo, Corbett, Croom, Croom, Di Matteo, Dunlop, Franceschini, Granato, Hewett, Ho, Ivezic, Jarvis, Kellermann, Lacy, Lahav, Laor, M. Magliocchetti, Magliocchetti, Magliocchetti, Magliocchetti, Marchesini, Marziani, Marziani, McLure, McLure, McLure, McLure, McLure, McLure, McLure, Miller, Oshlack, Porciani, R. B. Metcalf, Richards, Schade, Schneider, Silk, Snellen, Sulentic, White, Wold, Woo, Woo   +52 more
core   +3 more sources

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

An X-ray selected sample of radio-loud quasars [PDF]

, 2001
We construct the first X-ray selected sample of broad line radio-loud AGN from the EMSS survey. In order to test unifying schemes for radio-loud objects, their spectral and statistical properties (both flat and steep spectrum objects) are examined and ...
A. Celotti, A. Wolter, Avni, Becker, Boyle, Brinkmann, Caccianiga, Cavaliere, Celotti, Chiaberge, Condon, Della Ceca, Della Ceca, Dunlop, Fossati, Ghisellini, Ghisellini, Gioia, Gregory, Laurent-Muehleisen, Maccacaro, Maccacaro, Maraschi, Morris, Padovani, Padovani, Padovani, Perlman, Schmidt, Stark, Stocke, Stocke, Wall, Wolter   +33 more
core   +2 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

Hidden Blazars In Radio Loud Quasars? [PDF]

Symposium - International Astronomical Union, 2000
We present the initial results from our search for hidden blazars via CIV emission line variability among radio loud quasars. The implications on models of quasar Broad Emission Line Regions are discussed, and we focus on the tidally disrupted star model.
openaire   +1 more source

The Deep X-ray Radio Blazar Survey (DXRBS). II. New Identifications [PDF]

, 2000
We have searched the archived, pointed ROSAT Position Sensitive Proportional Counter data for blazars by correlating the WGACAT X-ray database with several publicly available radio catalogs, restricting our candidate list to serendipitous X-ray sources ...
Bignall, H., Giommi, P., Landt, H., Padovani, P., Perlman, E., Tzioumis, A.   +5 more
core   +3 more sources