scholarly journals Quasar Surveys

1986 ◽  
Vol 119 ◽  
pp. 17-32
Author(s):  
M. G. Smith
Keyword(s):  
Luminosity Function ◽  
Seyfert Galaxies ◽  
Radio Sources ◽  
Selection Effects ◽  
Spectral Evolution ◽  
X Ray ◽  
Spectrum Radio ◽  
Show Evidence ◽  
Optical Surveys ◽  
Radio Luminosity Function

A review is given of progress in surveys for quasars at frequencies from radio to x-ray. Radio results show evidence for a decline in the radio luminosity function for flat-spectrum radio sources at redshifts z > 2. The IRAS survey is uncovering hitherto unknown dusty Seyfert galaxies. Optical surveys, which yield the largest number of QSOs per square degree, may suffer from selection effects which depend on intrinsic luminosity, redshift, and spectral evolution - particularly above redshift 2. Below redshifts of about 2.3, the optical magnitude-redshift plane is being filled in to the point where the evolution of the luminosity function can be seen directly. The statistics of quasar pair separations provide the best evidence so far for quasar clustering.The existence of many potentially significant selection effects means that a multi-frequency approach to quasar surveys is likely to prove essential to an understanding of the evolutionary behaviour of the quasar population as a whole.

scholarly journals Flat-spectrum Radio Sources from the Parkes 2· 7 GHz Survey ? A Study of a Complete Sample

1990 ◽  
Vol 43 (2) ◽  
pp. 241 ◽  
Author(s):  
Ann Savage ◽  
David L Jauncey ◽  
Graeme L White ◽  
Bruce A Peterson ◽  
WL Peters ◽  
...  
Keyword(s):  
Early Universe ◽  
Galactic Plane ◽  
Radio Sources ◽  
Selection Effects ◽  
Complete Sample ◽  
Spectrum Radio ◽  
Optical Surveys

We describe our complete sample, taken from the Parkes 2�7 GHz catalogue, of flat-spectrum radio sources with flux densities > 0�5 Jy. The sample covers all right ascensions and declinations from +10� to -45�, excluding the galactic plane (lhI < 10�) and contains 403 sources. Attention is drawn to the advantages of radio surveys over optical surveys. The survey is used to highlight some selection effects found in optical surveys. We also discuss how this sample can be used to give us information on the early universe

scholarly journals Active Nuclei and Redshift Problems

1983 ◽  
Vol 6 ◽  
pp. 531-533
Author(s):  
Geoffrey Burbidge
Keyword(s):  
Galactic Nuclei ◽  
Seyfert Galaxies ◽  
Radio Sources ◽  
Powerful Radio ◽  
Radiation Mechanism ◽  
X Ray ◽  
Major Interest ◽  
Relativistic Particles

More than 20 years ago V. A. Ambartsumian proposed that much of the activity in galaxies was dominated and even generated by their nuclei. Subsequent observational work in radio, optical and x-ray frequencies has borne out his prophecy, and major interest has centered about the nature of the machine in the galactic nucleus. The major characteristic of this machine is that it releases energy rapidly and often spasmodically by processes which are not thermonuclear in origin.The original studies which led to the conclusion that nuclei were all important were observations of the powerful radio sources and Seyfert galaxies, and evidence for the ejection of gas from galaxies of many types. The realization that the synchrotron mechanism was the dominant radiation mechanism and the later studies of Compton radiation were fundamental in leading to the conclusion that large fluxes of relativistic particles must be generated in galactic nuclei.

scholarly journals Bulk Relativistic Motion in a Complete Sample of Radio Selected AGN

1987 ◽  
Vol 121 ◽  
pp. 287-293
Author(s):  
C.J. Schalinski ◽  
P. Biermann ◽  
A. Eckart ◽  
K.J. Johnston ◽  
T.Ph. Krichbaum ◽  
...  
Keyword(s):  
Dynamic Range ◽  
Radio Sources ◽  
Relativistic Motion ◽  
Complete Sample ◽  
Superluminal Motion ◽  
Spectrum Radio ◽  
Wide Range ◽  
Show Evidence

A complete sample of 13 flat spectrum radio sources is investigated over a wide range of frequencies and spatial resolutions. SSC-calculations lead to the prediction of bulk relativistic motion in all sources. So far 6 out of 7 sources observed with sufficient dynamic range by means of VLBI show evidence for apparent superluminal motion.

scholarly journals Cosmological evolution of the AGN kinetic luminosity function

2006 ◽  
Vol 2 (S238) ◽  
pp. 65-70
Author(s):  
Andrea Merloni ◽  
Sebastian Heinz
Keyword(s):  
Galaxy Formation ◽  
Luminosity Function ◽  
Cosmological Evolution ◽  
Energy Output ◽  
Theoretical Assumption ◽  
X Ray ◽  
Spectrum Radio ◽  
Luminosity Functions ◽  
Jet Power ◽  
Joint Evolution

AbstractWe present a first attempt to derive the cosmological evolution of the kinetic luminosity function of AGN based on the joint evolution of the flat spectrum radio and hard X-ray selected AGN luminosity functions. An empirical correlation between jet power and radio core luminosity is found, which is consistent with the theoretical assumption that, below a certain Eddington ratio, SMBH accrete in a radiatively inefficient way, while most of the energy output is in the form of kinetic energy.We show how the redshift evolution of the kinetic power density from such a low-ṁ mode of accretion makes it a good candidate to explain the so-called “radio mode” of AGN feedback as outlined in many galaxy formation schemes.

scholarly journals Statistical Effects of Doppler Beaming and Malmquist Bias on Flux-Limited Samples of Compact Radio Sources

1998 ◽  
Vol 164 ◽  
pp. 137-138
Author(s):  
Matthew L. Lister ◽  
Alan P. Marscher
Keyword(s):  
Active Galactic Nuclei ◽  
Luminosity Function ◽  
Galactic Nuclei ◽  
Lorentz Factor ◽  
Radio Sources ◽  
Apparent Velocity ◽  
Parent Population ◽  
Relativistic Jet ◽  
Spectrum Radio ◽  
Statistical Effects

AbstractWe examine the effects of Doppler beaming on flux-limited samples of compact extragalactic radio sources using Monte Carlo simulations. We incorporate a luminosity function and z-distribution for the parent population, and investigate models in which the unbeamed synchrotron luminosity L of a relativistic jet is related to its bulk Lorentz factor Γ. The predicted flux density, redshift, monochromatic luminosity, and apparent velocity distributions of our simulated flux-limited samples are compared to the Caltech-Jodrell Bank (CJF) sample of flat-spectrum, radio core-dominated active galactic nuclei (AGNs).We find that a relation between L and Γ is not needed to reproduce the characteristics of the CJF sample. Introducing a positive correlation between these quantities results in an underabundance of objects with high viewing angles, while a negative correlation gives generally poor fits to the data.

scholarly journals The X-ray Emission of Quasars as Observed by Ginga

1994 ◽  
Vol 159 ◽  
pp. 123-125
Author(s):  
A.J. Lawson ◽  
M.J.L. Turner
Keyword(s):  
Spectral Index ◽  
Rest Frame ◽  
Line Emission ◽  
Adequate Description ◽  
Rank Tests ◽  
X Ray ◽  
Spectrum Radio ◽  
Show Evidence ◽  
The Mean ◽  
The Relationship

We present preliminary results on a spectal analysis of quasars observed by the X-ray observatory Ginga. Simple power-law models with fixed Galactic absorbtion provide an adequate description of the spectra for most of the sources in the 2–18 keV band. A small number of sources show evidence for a feature at 6.4 keV (in the source rest frame) due to Fe line emission. Maximum likelihood and Spearman rank tests were used to investigate the relationship between radio loudness and X-ray spectral index in this class of object. These tests showed, respectively, that the mean X-ray spectral index of radio quiet quasars (RQQs) is significantly different from that of flat spectrum radio loud quasars (FRSQs) at the >99% level, and that the dominant relationship with spectral index is radio loudness (not X-ray luminosity or redshift) at >99% significance. This last result has not previously been demonstrated in this band, but agrees with findings in the lower energy Einstein band (0.5–3.5 keV). These results are discussed in the context of current unified models.

scholarly journals Radio Halos in Merging Clusters

2002 ◽  
Vol 12 ◽  
pp. 513-515 ◽  
Author(s):  
Gabriele Giovannini ◽  
Luigina Feretti
Keyword(s):  
Radio Sources ◽  
Clusters Of Galaxies ◽  
Diffuse Source ◽  
X Ray ◽  
Diffuse Sources ◽  
Physical Conditions ◽  
Show Evidence ◽  
Radio Halos

AbstractThe number of known diffuse radio sources in clusters of galaxies (halos and relics) has grown in recent years, making it possible to derive statistical considerations on the physical conditions of these sources and on the properties of related clusters. We will discuss the percentage of clusters with a diffuse source and will show evidence that diffuse sources are associated with X-ray luminous clusters which have undergone recent merger processes.

An X-ray survey of flat spectrum radio sources

1981 ◽  
Vol 30 (1-4) ◽  
pp. 33-37 ◽  
Author(s):  
Peter Biermann
Keyword(s):  
Radio Sources ◽  
X Ray ◽  
Spectrum Radio
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