The radio counter-jet of the QSO 3C 48

¹ Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030, PR China e-mail: wfeng@shao.ac.cn
² Graduate School of Chinese Academy of Sciences, Beijing 100039, PR China
³ National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, PR China
⁴ Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS 78, Cambridge, MA 02138, USA
⁵ Istituto di Radioastronomia del CNR, via Gobetti 101, 4129 Bologna, Italy

Received: 5 November 2004
Accepted: 9 December 2004

Abstract

We present multi-frequency radio observational results of the quasar 3C 48. The observations were carried out with the Very Large Array (VLA) at five frequencies, 0.33, 1.5, 4.8, 8.4, and 22.5 GHz, and with the Multi-Element Radio Linked Interferometer Network (MERLIN) at the two frequencies of 1.6 and 5 GHz. The source shows a one-sided jet to the north within 1´´, which then extends to the northeast and becomes diffuse. Two bright components (N2 and N3), containing most of the flux density, are present in the northern jet. The spectral index of the two components is and (). Our images show the presence of an extended structure surrounding component N2, suggestive of strong interaction between the jet and the interstellar medium (ISM) of the host galaxy. A steep-spectrum component, labelled S, located 0.25'' southwest to the flat-spectrum component which could be the core of 3C 48, is detected at a significance of >. Both the location and the steepness of the spectrum of component S suggest the presence of a counter-jet in 3C 48.