The radio structure of radio-quiet quasars

¹ AIRUB, University of Bochum, Universitätsstrasse 150, 44780 Bochum, Germany e-mail: [leipski;nbennert;huette]@astro.rub.de
² Radio Observatory Westerbork, ASTRON, PO Box 2, 7990 AA Dwingeloo, The Netherlands e-mail: falcke@astron.nl
³ Department of Astrophysics, Radboud University, 6525 ED Nijmegen, The Netherlands
⁴ Institute of Geophysics and Planetary Physics, University of California, Riverside, CA 92521, USA e-mail: nicola.bennert@ucr.edu

Received: 5 October 2005
Accepted: 26 April 2006

Abstract

Aims.We investigate the radio emitting structures of radio-quiet active galactic nuclei with an emphasis on radio-quiet quasars to study their connection to Seyfert galaxies.

Methods.We present and analyse high-sensitivity VLA radio continuum images of 14 radio-quiet quasars and six Seyfert galaxies.

Results.Many of the low redshift radio-quiet quasars show radio structures that can be interpreted as jet-like outflows. However, the detection rate of extended radio structures on arcsecond scales among our sample decreases with increasing redshift and luminosity, most likely due to a lack of resolution. The morphologies of the detected radio emission indicate strong interactions of the jets with the surrounding medium. We also compare the radio data of seven quasars with corresponding HST images of the [] emitting narrow-line region (NLR). We find that the scenario of interaction between the radio jet and the NLR gas is confirmed in two sources by structures in the NLR gas distribution as previously known for Seyfert galaxies. The extended radio structures of radio-quiet quasars at sub-arcsecond resolution are by no means different from that of Seyferts. Among the luminosities studied here, the morphological features found are similar in both types of objects while the overall size of the radio structures increases with luminosity. This supports the picture where radio-quiet quasars are the scaled-up versions of Seyfert galaxies. In addition to known luminosity relations we find a correlation of the NLR size and the radio size shared by quasars and Seyferts.