Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992aas...181.1509l&link_type=abstract
American Astronomical Society, 181st AAS Meeting, #15.09; Bulletin of the American Astronomical Society, Vol. 24, p.1144
Astronomy and Astrophysics
Astronomy
1
Scientific paper
In an effort to better understand the properties of radio galaxies in rich-cluster enviroments, we have surveyed a complete sample of radio galaxies in Abell clusters. The survey consists of two parts: for z < 0.09, all radio galaxies with 20 cm flux densities > 10 mJy within 0.3 corrected Abell radii of the cluster center. For higher redshifts (0.09 < z < 0.20), we have included all galaxies > 200 mJy out to 0.5 Abell radii. These two samples consist of about 325 radio galaxies. We are combining both VLA imaging and CCD surface photometry to study the parent populations for these sources. We have chosen a three-parameter set of observed properties which will be used to test standard models for radio-source evolution and to construct an H-R like diagram for radio galaxies. These parameters are the radio luminosity, radio size, and R-band optical magnitude. For a complete sample, the density of points in such a diagram should be related to the amount of time a source spends in each state. By examining these properties as a function of radio morphology, an evolutionary scheme might be found. In the Radio Luminosity vs. Optical Magnitude diagram, we find a sharp division between the FR I and FR II radio galaxies which is a function of both radio and optical luminosity. This result appears to hold for radio galaxies both in and out of cluster enviroments. The slope of this break suggests a relation like Lradio ~ Loptical(2) . Past studies of the bivariate luminosity function for radio galaxies have shown a break in the function at a radio power P(*) ~ 10(25) W Hz(-1) . We find that P(*) is a strong function of optical luminosity, and follows the FR I/FR II break. Our data also suggests that the slope for P < P(*) may flatten for decreasing optical luminosity. The sharpness of this break may suggest some evolutionary relation between the two types of sources. By adding the radio size to this analysis, we should be able to test this hypothesis.
Ledlow Michael J.
Owen Frazer N.
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