Physics
Scientific paper
Oct 1999
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999phdt.........6h&link_type=abstract
Thesis (PhD). UNIVERSITY OF COLORADO AT BOULDER, Source DAI-B 60/04, p. 1649, Oct 1999, 274 pages.
Physics
2
Revised 3Rd Catalog Of Radio Sources, Galaxy Clustering, Remote Sensing
Scientific paper
Optical and radio images have been gathered for a nearly complete sample of radio galaxies in the redshift range 0.15 < z < 0.65. The sample was taken from the Revised 3rd Cambridge (3CR) Catalog of Radio Sources. Total, host, and nuclear magnitudes and colors have been extracted from the optical images. The richness of the clustering environment around the objects has also been quantified by calculating the amplitude of the galaxy-galaxy spatial covariance function (Bgg) from the optical images. Radio structure parameters such as largest physical size, projected bending angle, lobe length asymmetry and hot spot placement have been measured from the highest quality radio maps available. These optical and radio data are compared to similar data from an existing sample of quasars in the same redshift range for the purpose of determining the relationship between radio galaxies and quasars. This comparison appears to rule out the hypothesis that all quasars are radio galaxies viewed from a particular angle and supports the hypothesis that quasars dim with time and eventually evolve into radio galaxies. The radio galaxy and quasar samples are then merged and the environmental and radio data are used to search for evidence of gas within the clustering environment (a.k.a. an intracluster medium or ICM) by looking for confinement and distortions of the radio structure that are correlated with the richness of the clustering environment. angle cannot be used as an indicator of a rich clustering environment as has been suggested previously. A radio survey of a sample of 19 Einstein Extended Medium Sensitivity Survey (EMSS) clusters in the redshift range 0.3 < z < 0.83 (which are some of the richest clusters known at these redshifts) provides information on the radio sources in extremely rich clustering environments. The survey shows all radio sources judged to be in these clusters to be of the FR1 type. These radio sources are compared to those in extremely rich clusters at the current epoch for the purpose of determining the evolution of radio sources in the richest clustering environments. This comparison shows that there has been very little, if any, evolution in the individual radio source properties (luminosities, morphologies, core dominance values and largest angular sizes), the spatial distribution of the radio galaxies within their respective clusters and the total number of radio galaxies in extremely rich environments since z ~ 0.5. These EMSS cluster radio sources (which are known to be surrounded by a dense ICM because the EMSS is an X-ray survey) are also compared (qualitatively) with the 3CR radio galaxies and the quasars (which have much weaker ICMs, if any at all) to further investigate the effect of the ICM on the radio structure. This comparison strongly supports the idea that a dense ICM affects the radio structure because the EMSS cluster sources all have an FR1 type radio structure while the 3CR radio galaxies and the quasars typically have an FR2 type. Based on this, it is plausible that interactions with a thickening ICM could cause an FR2 type radio source to evolve into an FR1 type. (Abstract shortened by UMI.)
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