The parsec-scale properties of the radio galaxy 4C 26.42 in the dense cooling core cluster A1795

¹ Istituto di Radioastronomia, INAF, 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

Received: 27 February 2009
Accepted: 9 May 2009

Abstract

Aims. The aim of the present work is to study the radio emission on the parsec scale of 4C 26.42, the Brightest cluster galaxy in Abell 1795, in the framework of radiosources in a dense cool core cluster.

Methods. We present Very Long Baseline Array (VLBA) observations at 1.6, 5, 8.4 and 22 GHz. We performed a spectral index and multiepoch analysis.

Results. The source appears two-sided with a well defined and symmetric Z-structure at ~5 mas from the core. The kiloparsec-scale morphology is similar to the parsec-scale structure, but reversed in PA, with symmetric 90° bends at about 2 arcsec from the nuclear region. Comparing data obtained at 3 different epochs we derive a 3σ limit to the apparent proper motion of  < 0.04. We suggest that the parsec-scale jets are sub-relativistic, in contrast with the high velocities found for most low-power radio galaxies. The origin of the unusual radio morphology remains a puzzle. We suggest that the identification of the parent galaxy with the central cD in a cooling cluster plays an important role in the properties and structure of the jets.