Surface photometry of radio galaxies – II. Cluster sources

Abstract

CCD surface photometry of 52 radio galaxies in the R-band is reported. The project was designed to study the parent galaxies of radio sources in rich clusters of galaxies and to compare the results with our earlier study of FR I and FR II sources. A radio versus optical luminosity plot shows the same division between FR I and FRII radio sources much more clearly because of the larger sample. A good correlation between radio and optical luminosity is evident for the FR I sources alone but, as reported earlier, FR II sources do not fit this correlation. The results from the larger data set suggest that the FR I/FR II break may be a function of both radio and optical luminosity. The parent galaxies of all the radio sources studied seem to form a one-parameter family with no differences in galaxies inside and outside clusters except that optically brighter galaxies seem to occur more often in rich clusters. The fainter optical galaxies near L* fit r1/4 laws well, while more luminous galaxies deviate toward D-like structures. This change in structure seems to be smoothly correlated with increasing luminosity. There is also a trend for the more luminous galaxies to be more elongated. Classical Double sources in our sample are associated with the lowest optical luminosities near L*. Narrow Angle Tail sources and Twin Jets are associated with intermediate optical luminosities, while the most radio-loud Twin Jet sources are found in the most luminous optical galaxies. More distorted sources such as Narrow Angle Tail sources and Bent Twin Jets or Wide Angle Tail sources clearly occur more often in rich clusters; however, they seem to fit into the correlation between radio and optical luminosity independent of their structure.