An X-ray selected list of QSOs: Implications for the QSO luminosity function and the origin of the diffuse X-ray background

1981 ◽  
Vol 30 (1-4) ◽  
pp. 59-59
Author(s):  
Bruce Margon ◽  
Gary Chanan ◽  
Ronald Downes
Keyword(s):  
Luminosity Function ◽  
X Ray ◽  
X Ray Background

scholarly journals UHURU Results on Extragalactic X-Ray Sources

1973 ◽  
Vol 55 ◽  
pp. 171-183 ◽  
Author(s):  
Edwin M. Kellogg
Keyword(s):  
High Latitude ◽  
Luminosity Function ◽  
Optical Data ◽  
Clusters Of Galaxies ◽  
X Rays ◽  
Total Contribution ◽  
X Ray ◽  
Normal Galaxies ◽  
X Ray Background ◽  
Individual Galaxies

Data from the UHURU satellite have provided a list of more than forty high latitude sources (|b| > 20°). X-rays have been detected from among the nearest normal galaxies, giant radio galaxies, Seyferts, QSOs and clusters of galaxies. The cluster sources appear to be extended by several hundred kiloparsecs as well as being very luminous. These cluster sources have systematic differences in their X-ray spectra from individual galaxies.About twenty sources are not reliably identified so far. A few of these are located near undistinguished 3C or MSH radio sources. The rest are either located near distant clusters or undistinguished bright galaxies, or are too far south, so that we have not sufficient optical data to allow a thorough search for possible association with clusters or unusual individual galaxies.The luminosity function for weak, high latitude X-ray sources is determined, and the contribution of sources just below the UHURU threshold of detectability to observed fluctuations in the diffuse X-ray background is evaluated. The total contribution of all observed types of extragalactic sources to the X-ray background is estimated.

scholarly journals The X-Ray Background and the AGN Luminosity Function

1999 ◽  
Vol 183 ◽  
pp. 200-209
Author(s):  
G. Hasinger
Keyword(s):  
Black Holes ◽  
Luminosity Function ◽  
Cosmic Time ◽  
Volume Density ◽  
Energy Bands ◽  
X Ray ◽  
Normal Galaxies ◽  
X Ray Background ◽  
Acid Test

ROSAT deep and shallow surveys have provided an almost complete inventory of the constituents of the soft X-ray background which led to a population synthesis model for the whole X-ray background with interesting cosmological consequences. According to this model the X-ray background is the “echo” of mass accretion onto supermassive black holes, integrated over cosmic time. A new determination of the soft X-ray luminosity function of active galactic nuclei (AGN) is consistent with pure density evolution, and the comoving volume density of AGN at redshift 2–3 approaches that of local normal galaxies. This indicates that many larger galaxies contain black holes and it is likely that the bulk of the black holes was produced before most of the stars in the universe. However, only X-ray surveys in the harder energy bands, where the maximum of the energy density of the X-ray background resides, will provide the acid test of this picture.

scholarly journals Constraints on Very Faint High-z Quasars

2006 ◽  
Vol 2 (14) ◽  
pp. 261-261
Author(s):  
Mark Dijkstra
Keyword(s):  
Luminosity Function ◽  
High Redshift ◽  
X Ray ◽  
X Ray Background

AbstractI discuss the constraints that can be derived on the abundance of high redshift (z>6) (mini)quasars from the unresolved soft X-Ray background. Furthermore, I will show how existing Lyα surveys can be used to probe the very faint MB≳-21 mag (i.e., ≳7–8 mag fainter than the SDSS quasars) end of the z≥,4.5 quasar luminosity function.

The properties of X-ray-selected active galactic nuclei. I - Luminosity function, cosmological evolution, and contribution to the diffuse X-ray background

1991 ◽  
Vol 374 ◽  
pp. 117 ◽  
Author(s):  
Tommaso Maccacaro ◽  
Roberto della Ceca ◽  
Isabella M. Gioia ◽  
Simon L. Morris ◽  
John T. Stocke ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Luminosity Function ◽  
Galactic Nuclei ◽  
Cosmological Evolution ◽  
X Ray ◽  
X Ray Background

scholarly journals The Palomar Observatory Dwarf Seyfert Survey

1994 ◽  
Vol 159 ◽  
pp. 275-278
Author(s):  
Luis C. Ho ◽  
Alexei V. Filippenko ◽  
Wallace L. W. Sargent
Keyword(s):  
Active Galactic Nuclei ◽  
Luminosity Function ◽  
Galactic Nuclei ◽  
Statistical Properties ◽  
X Ray ◽  
Preliminary Results ◽  
Methods Of Analysis ◽  
Nearby Galaxies ◽  
X Ray Background

We describe an optical, spectroscopic survey of the nuclei of the 500 brightest galaxies in the northern sky. The primary goal is to search for low-luminosity active galactic nuclei (LLAGNs) in the centers of nearby galaxies. The results of this survey will have many astrophysical applications, including quantifying the faint end of the local AGN luminosity function and estimating the contribution of LLAGNs to the X-ray background. We summarize the statistical properties of the survey, describe our methods of analysis, and present some preliminary results based on ∼ 60% of the sample.

scholarly journals Cosmic Distribution of Optically Selected Quasars

1987 ◽  
Vol 124 ◽  
pp. 619-625
Author(s):  
Maarten Schmidt
Keyword(s):  
Luminosity Function ◽  
Birth Rate ◽  
Emission Lines ◽  
Short Life ◽  
Large Redshift ◽  
X Ray ◽  
Wide Range ◽  
X Ray Background ◽  
Spectral Survey ◽  
Luminosity Evolution

Counts of optically selected quasars as a function of magnitude and redshift show the effects of strong evolution. If quasars have relatively short life times, then the observed numbers at a given redshift are mostly determined by their birth rate and mean luminosity over their lifetime. In this case the evolution of the luminosity function can be described by density evolution, where the rate of evolution may depend on luminosity and other properties. On the other hand, if all quasars were formed at large redshift and have been decaying in luminosity since that time, then the evolution of the luminosity function is best described in terms of luminosity evolution. We discuss some of the consequences of luminosity evolution for the mass of quasars and for the X-ray background.We explore the observational aspects of the redshift cutoff of quasars. The situation is complicated by the unavoidable bias in slitless surveys against weak-line objects. Since quasar emission lines show a wide range of equivalent widths, a spectral survey will be characterized by a distribution of limiting continuum magnitudes rather than by a single value. The decline in the space density of quasars at large redshift may depend on luminosity, and may also have structure, such as a steep drop, but not a total cutoff, in density at a redshift near 3.

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