B2 1144+35B, a giant low power radio galaxy with superluminal motion

Orientation and evidence for recurrent activity

¹ Dipartimento di Astronomia, Universita' di Bologna, via Ranzani 1, 40127 Bologna, Italy e-mail: ggiovann@ira.inaf.it
² Istituto di Radioastronomia – INAF, via Gobetti 101, 40129 Bologna, Italy
³ Department of Physics and Astronomy, University of New Mexico, Albuquerque, NM 87131, USA

Received: 11 June 2007
Accepted: 3 August 2007

Abstract

Aims.The goal of this work is a detailed study of the nearby, low power radio galaxy B2 1144+35B.

Methods.For this purpose, we performed new Very Long Baseline Array (VLBA) and Very Large Array (VLA) observations.

Results.This source has several properties (bright, nearby, large range of spatial structures, visible counterjet, etc.) that make it an excellent astrophysical laboratory for the study of the evolution of radio jets. Here we report the detection of motion in the counterjet at  c, which allows us to estimate the orientation of the parsec-scale jet at 33 from the line of sight, with an intrinsic velocity of (0.94)c. We also report on a brightening of the core at high frequencies which we suggest could be the result of a new component emerging from the core. High dynamic range VLBA observations at 5 GHz reveal, for the first time, extended emission connecting the core with the bright complex of emission that dominates the flux density of the parsec scale structure at frequencies below 20 GHz. The evolution of this bright complex is considered and its slow decline in flux density is interpreted as the result of an interaction with the interstellar medium of the host galaxy.