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

¹ INAF – Istituto di Radioastronomia, via Gobetti 101, 40129 Bologna, Italy
e-mail: liuzzo@ira.inaf.it
² INAF – Osservatorio Astronomico di Padova, vicolo dell Osservatorio 5, 35122 Padova, Italy
³ Dipartimento di Astronomia, Universitá di Bologna, via Ranzani 1, 40127 Bologna, Italy
⁴ INAF – Osservatorio Astronomico di Torino, via Osservatorio 20, 10025 Pino Torinese, Italy
⁵ Department of Physics and Astronomy, University of New Mexico, Albuquerque NM 87131, USA

Received: 13 July 2012
Accepted: 18 September 2012

Abstract

Context. Among radio galaxies, compact sources are a class of objects that are not yet well understood, and most of them cannot be included in classical populations of compact radio sources (flat-spectrum or compact steep-spectrum sources).

Aims. Our main goal is to analyze the radio and optical properties of a sample of compact sources and compare them with Faranoff-Riley I and II extended radio galaxies.

Methods. We selected in the Bologna Complete Sample a subsample of compact sources, naming it the C BCS sample. We collected new and literature subarcsecond resolution multi-frequency VLA images and optical data. We compared total and nuclear radio power with optical emission line measurements.

Results. 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 as core radio galaxies, but with a higher radio power.

Conclusions. The 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 on the presence of dense environments (e.g., cluster or HI-rich galaxies) and on a young age or restarted radio activity.