Compact sources in the Bologna Complete Sample: high-resolution VLA observations and optical data

Abstract

Among radio galaxies, compact sources are a class of objects not yet well understood, and most of them cannot be included in classical populations of compact radio sources (flat spectrum AGN or compact steep spectrum sources). Our main goal is to analyze the radio and optical properties of a sample of compact sources and compare them with FRI/FRII extended radio galaxies. We selected in the Bologna Complete Sample a sub sample of Compact sources, naming it the C BCS sample. We collected new and literature sub-arcsecond resolution multi-frequency VLA images and optical data. We compared total and nuclear radio power with optical emission line measurements. The [OIII] luminosity - 408 MHz total power relation found in High and Low excitation galaxies, as well as in young (CSS) sources, holds also for the C BCSs. However, C BCSs present higher [OIII] luminosity than expected at a given total radio power, and they show the same correlation of Core Radio Galaxies, but with a higher radio power. C BCSs appear to be the high power tail of Core Radio Galaxies. For most of the C BCSs, the morphology seems to be strongly dependent to the presence of dense environments (e.g. cluster or HI-rich galaxies) and to a low age or restarted radio activity.