Parsec-scale properties of brightest cluster galaxies

¹ INAF Istituto di Radioastronomia, via Gobetti 101, 40129 Bologna, Italy e-mail: liuzzo@ira.inaf.it
² Dipartimento di Astronomia, Università di Bologna, via Ranzani 1, 40127 Bologna, Italy
³ Department of Physics and Astronomy, University of New Mexico, Albuquerque NM 87131, USA
⁴ also Adjunct Astronomer at the National Radio Astronomy Observatory, USA

Received: 16 December 2009
Accepted: 1 February 2010

Abstract

We present new VLBI observations at 5 GHz of a complete sample of brightest cluster galaxies (BCGs) in nearby Abell clusters (distance class <3). Combined with data from the literature, we provide parsec-scale information for 34 BCGs. Our analysis of the parsec-scale radio emission of BCGs and the cluster X-ray properties finds a possible dichotomy between BCGs in cool-core clusters and those in non-cool-core clusters. Among resolved sources, those in cool-core clusters tend to have two-sided parsec-scale jets, while those in less relaxed clusters have predominantly one-sided parsec-scale jets. We suggest that this difference is caused by the interplay between the jets and the surrounding medium. The one-sided structure in non-cool-core clusters may be due to Doppler boosting effects in relativistic, intrinsically symmetric jets whereas two-sided morphology in cool core clusters is probably related to the presence of heavy and mildly relativistic jets that have been decelerated on the parsec-scale. Evidence of recurrent activity is also found in BCGs in cool-core clusters.