Results 41 to 50 of about 10,384 (186)
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
Radio Observations of 4079 Quasars [PDF]
, 1997 Using the NVSS radio catalog, we have searched for radio emission from 4079 quasars taken from the 1996 version of the Veron-Cetty and Veron (1996) quasar catalog. The comparison resulted in the positive detection of radio emission from 799 quasars.
Becker, Robert H., Bischof, Otto B.
core +3 more sources
Evidence for AGN Feedback in Galaxy Clusters and Groups
Advances in Astronomy, Volume 2012, Issue 1, 2012., 2012 The current generation of flagship X‐ray missions, Chandra and XMM-Newton, has changed our understanding of the so‐called “cool‐core” galaxy clusters and groups. Instead of the initial idea that the thermal gas is cooling and flowing toward the center, the new picture envisages a complex dynamical evolution of the intracluster medium (ICM) regulated by
Myriam Gitti +3 more
wiley +1 more source
Unveiling Radio Loudness in Quasars
, 2003 We present a new approach to tackle the issue of radio loudness in quasars. We constrain a (simple) prescription for the intrinsic distribution of radio-to-optical ratios by comparing properties of Monte Carlo simulated samples with those of observed optically selected quasars.
Cirasuolo, M. +3 more
openaire +2 more sources
Radio-loud and radio-quiet quasars observed by EXOSAT [PDF]
Monthly Notices of the Royal Astronomical Society, 1992 We present results from the spectral analysis of EXOSAT data on 31 quasars, 18 radio-loud and 13 radio-quiet. Simple power-law models with fixed (Galactic) absorption give acceptable fits to the spectra obtained in the 2-10 keV band. Using the results from these fits we have compared the distributions of spectral indices α for the radio-loud and radio ...
A. J. Lawson +4 more
openaire +1 more source
Phylogenetic Analyses of Quasars and Galaxies
Frontiers in Astronomy and Space Sciences, 2017 Phylogenetic approaches have proven to be useful in astrophysics. We have recently published a Maximum Parsimony (or cladistics) analysis on two samples of 215 and 85 low-z quasars (z < 0.7) which offer a satisfactory coverage of the Eigenvector 1 ...
Didier Fraix-Burnet +2 more
doaj +1 more source
The Astrophysical Journal, 2023 Dual and off-nucleus active supermassive black holes are expected to be common in the hierarchical structure formation paradigm, but their identification at parsec scales remains a challenge due to strict angular resolution requirements.
Yu-Ching Chen +7 more
doaj +1 more source
Gravitational Lensing as a Probe of Cold Dark Matter Subhalos
Advances in Astronomy, Volume 2010, Issue 1, 2010., 2010 In the cold dark matter scenario, dark matter halos are assembled hierarchically from smaller subunits. Some of these subunits are disrupted during the merging process, whereas others survive temporarily in the form of subhalos. A long‐standing problem with this picture is that the number of subhalos predicted by simulations exceeds the number of ...
Erik Zackrisson +2 more
wiley +1 more source
The Case for Two Quasar Populations
Open Astronomy, 2011 We present evidence for two populations of quasars showing distinctly different broad line structure and kinematics. The first evidence for quasar dichotomy involve differences between radio-quiet and radio-loud sources.
Sulentic Jack +2 more
doaj +1 more source
Blueshifted Fe ii and Balmer Broad Emission lines in a Reddened Quasar
The Astrophysical Journal, 2023 We present detailed analysis of the optical and near-infrared spectrum of the reddened radio-loud quasar F2M J154043.74+492323.9 with strong optical Fe ii emission of ${R}_{4570}\equiv \tfrac{\mathrm{Fe}\,{\rm\small{II}}\lambda \lambda \,4434,4684}{{\rm ...
Yipeng Zhou +3 more
doaj +1 more source