Results 31 to 40 of about 796,792 (175)

The Pan-STARRS1 z > 5.6 Quasar Survey. II. Discovery of 55 Quasars at 5.6 < z < 6.5

The Astrophysical Journal Supplement Series, 2023
The identification of bright quasars at z ≳ 6 enables detailed studies of supermassive black holes, massive galaxies, structure formation, and the state of the intergalactic medium within the first billion years after the Big Bang.
Eduardo Bañados, Jan-Torge Schindler, Bram P. Venemans, Thomas Connor, Roberto Decarli, Emanuele Paolo Farina, Chiara Mazzucchelli, Romain A. Meyer, Daniel Stern, Fabian Walter, Xiaohui Fan, Joseph F. Hennawi, Yana Khusanova, Nidia Morrell, Riccardo Nanni, Gaël Noirot, Antonio Pensabene, Hans-Walter Rix, Joseph Simon, Gijs A. Verdoes Kleijn, Zhang-Liang Xie, Da-Ming Yang, Andrew Connor   +22 more
doaj   +1 more source

The optical variability of radio-loud quasars [PDF]

Proceedings of the International Astronomical Union, 2012
AbstractThe optical variability of a sample of 44 FSRQs and 18 SSRQs in the SDSS stripe 82 region is investigated by using the multi-epoch data covering nine years. The variabilities are clearly detected in each source with the amplitude in r band, from 0.18 to 3.46 mag.
Minfeng Gu, Y. L. Ai
openaire   +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

Herschel-ATLAS*: far-infrared properties of radio-loud and radio-quiet quasars [PDF]

, 2014
We have constructed a sample of radio-loud and radio-quiet quasars from the Faint Images Radio Sky at Twenty-one centimetres and the Sloan Digital Sky Survey Data Release 7, over the Herschel-ATLAS Phase 1 area (9h, 12h and 14. h 5).
de Zotti, G, Dunne, Loretta, Valiante, Elisabetta, Stevens, JA, Ibar, E, Valiante, E, de Zotti, G., Maddox, S., Smith, DJB, Ivison, RJ, Jarvis, M. J., Valiante, E., Smith, Daniel, Jarvis, M.J., Hardcastle, M.J., Hardcastle, M. J., Smith, M. W. L., Ibar, E., Smith, D. J. B., Hardcastle, MJ, Eales, Stephen Anthony, Ivison, R. J., Kalfountzou, E, Eales, S., Smith, Matthew W., Stevens, J.A., Maddox, S, Maddox, Steve, Kalfountzou, E., Bourne, N., Jarvis, MJ, Dunne, L., Ivison, R.J., Stevens, J. A., Bourne, N, Eales, S, Dunne, L, Smith, MWL   +37 more
core   +1 more source

The Fundamental Planes of Black Hole Activity for Radio-Loud and Radio-Quiet Quasars

, 2022
We examine the fundamental plane of black hole activity for correlations with redshift and radio loudness in both radio-loud and radio-quiet quasar populations.
Siemiginowska, Aneta, Bradford Snios, Aneta Siemiginowska, Sobolewska, Małgosia, Małgosia Sobolewska, Luis Gabriel C Bariuan, Bariuan, Luis Gabriel C., Schwartz, Daniel A., Daniel A Schwartz, Snios, Bradford   +9 more
core   +1 more source

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

Evidence for Higher Black Hole Spin in Radio-loud Quasars [PDF]

, 2017
One of the major unsolved questions concerning the understanding of the active galactic nucleus population is the origin of the dichotomy between radio-quiet and radio-loud quasars.
Lu, Youjun, Chris Done, Yoshiyuki Inoue, Andreas Schulze, Zhang, Fupeng, Fupeng Zhang, Done, Chris, Inoue, Yoshiyuki, Schulze, Andreas, Youjun Lu   +9 more
core   +1 more source

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

A Practical Guide to the Massive Black Hole Cosmic History

Advances in Astronomy, Volume 2012, Issue 1, 2012., 2012
I review our current understanding of massive black hole (MBH) formation and evolution along the cosmic history. After a brief introductory overview of the relevance of MBHs in the hierarchical structure formation paradigm, I discuss the main viable channels for seed BH formation at high redshift and for their subsequent mass growth and spin evolution.
A. Sesana, Francesco Shankar
wiley   +1 more source