Impact of the local environment on the properties of radio galaxies: a study of galaxies identified from the Texas Survey

A sample of 3196 radio sources, with absolute value b greater than or equal to 200 from the +360 strip of the 365 MHz Texas Survey, searched for optical counterparts, forms a large homogeneous data base used to investigate the incidence of and importance of, as a class of radio sources, optically first ranked galaxies occurring in small groups. The optical identification rate, for this sample, is 27%, with the identifications equally divided into red (galaxies) and blue (QSO and QSO-like) objects. Statistical tests show that the galaxies and QSO plus QSO-like objects come from different radio populations and that their distribution of number as a function of apparent magnitude is different. Detailed optical and radio observations of a subset of twenty of the radio galaxies shows that the vast majority, probably all, are in interacting systems and that local environment plays a definite role. Divided by optical morphology, the combined optical luminosity of an interacting system is correlated with its radio luminosity. Examples taken from the literature confirm and extend these correlations to cluster radio galaxies. Using the sample of twenty to calibrate the entire sample of identified radio galaxies (405), a bivariate radio luminosity function was constructed