Results 101 to 110 of about 367,227 (284)
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
Revisiting the Fraction of Radio-Loud Narrow Line Seyfert 1 Galaxies with LoTSS DR1
Universe, 2020 Radio-Loud narrow-line Seyfert 1 galaxies (NLS1s), especially the extremely radio-loud ones, are widely accepted as the jetted versions of NLS1s. We explore the radio-loud fraction for NLS1s with recently released LoTSS DR1 at 150 MHz.
Xu-Liang Fan
doaj +1 more source
Seyfert galaxies in UZC-Compact Groups [PDF]
Astronomy & Astrophysics, 2004 We present results concerning the occurrence of Seyfert galaxies in a new automatically selected sample of nearby Compact Groups of galaxies (UZC-CGs). Seventeen Seyferts are found, constituting ~3% of the UZC-CG galaxy population. CGs hosting and non-hosting a Seyfert member exhibit no significant differences, except that a relevant number of Sy2 is ...
KELM, BIRGIT, FOCARDI, PAOLA, ZITELLI V.
openaire +4 more sources
Optical Variability of Narrow-line and Broad-line Seyfert 1 Galaxies [PDF]
, 2017 We studied the optical variability (OV) of a large sample of narrow-line Seyfert 1 (NLSy1) and broad-line Seyfert 1 (BLSy1) galaxies with z < 0.8 to investigate any differences in their OV properties.
S. Rakshit, C. .. Stalin
semanticscholar +1 more source
Clustering of X‐Ray‐Selected AGN
Advances in Astronomy, Volume 2012, Issue 1, 2012., 2012 The study of the angular and spatial structure of the X‐ray sky has been under investigation since the times of the Einstein X‐ray Observatory. This topic has fascinated more than two generations of scientists and slowly unveiled an unexpected scenario regarding the consequences of the angular and spatial distribution of X‐ray sources.
N. Cappelluti +3 more
wiley +1 more source
The Unified model and the Seyfert 2 infrared dichotomy [PDF]
Mon.Not.Roy.Astron.Soc. 320 (2001) L15, 2000 An optical spectropolarimetric study has shown that the detectability of polarised broad H-alpha in Seyfert 2 galaxies is correlated to the IRAS f60/f25 flux ratio where only those Seyfert 2s with "warm" IRAS colours show polarised broad line emission.
arxiv +1 more source
The Astrophysical JournalWe analyze a sample of ~113,000 galaxies ( z
Huynh Anh N. Le, Yongquan Xue
doaj +1 more source
The Astrophysical Journal, 2023 Some Seyfert galaxies are detected in high-energy gamma rays, but the mechanism and site of gamma-ray emission are unknown. Also, the origins of the cosmic high-energy neutrino and MeV gamma-ray backgrounds have been veiled in mystery since their ...
Hiromichi Tagawa +2 more
doaj +1 more source
Symposium - International Astronomical Union, 1989 We present data for Seyfert and normal galaxies in the Revised Shapley-Ames Catalog. The type 2 Seyferts are stronger CO and Far-IR emitters (by factors of 2–4) than either normal galaxies or type 1 Seyferts. The Seyfert CO line-widths correlate with both the 21cm HI and [OIII]5007 line-widths.
openaire +1 more source
The difference between the narrow line region of Seyfert 1 and Seyfert 2 galaxies [PDF]
, 1998 This paper presents a comparative study of emission line ratios of the Narrow Line Region (NLR) of Seyfert 1 and Seyfert 2 galaxies. It includes a literature compilation of the emission line fluxes [OII]3727A, [NeIII]3869A, [OIII]5007A and [NeV]3426A, as well as 60mum continuum flux, for a sample of 52 Seyfert 1's and 68 Seyfert 2's.
arxiv +1 more source