Astron. Astrophys. Suppl. Ser. 137, 457-471

Radio continuum morphology of southern Seyfert galaxies

R. Morganti¹ - Z.I. Tsvetanov² - J. Gallimore³ - M.G. Allen⁴

Send offprint request: R. Morganti

1 - Istituto di Radioastronomia, CNR, Via Gobetti 101, 40129 Bologna, Italy
e-mail: rmorgant@ira.bo.cnr.it
2 - Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, U.S.A.
3 - NRAO, 520 Edgemont Rd., Charlottesville, VA 22903, U.S.A.
4 - Mount Stromlo and Siding Spring Observatories, Private Bag, Weston Creek Post Office, ACT 2611, Australia

Received October 19, 1998; accepted April 16, 1999

Abstract:

We present radio observations for 29 southern Seyfert galaxies selected from a volume limited sample with cz<3600 km s^-1, and declination $\delta<0\hbox{$^\circ$}$. Objects with declination $-30\hbox{$^\circ$}<\delta<0\hbox{$^\circ$}$ were observed with the Very Large Array (VLA) at 6 cm (4.9 GHz) and objects with $\delta<-30\hbox{$^\circ$}$ were observed with the Australia Telescope Compact Array (ATCA) at 3.5 cm (8.6 GHz). Both the VLA and the ATCA observations have a resolution of $\sim 1\hbox{$^{\prime\prime}$}$. These new observations cover more than 50% of the southern sample with all but two of the 29 objects detected above our limit of 0.15 mJy. Combining these data with data available from the literature gives almost 85% coverage of the southern sample and further expands the radio observations of a distance limited sample by 22%.

Collecting additional sources from the literature, consisting of known Seyferts with cz < 4600 km s^-1, we find that 38% of the sources are unresolved at arcsecond resolution, and 34% have linear radio structure. Our results expand upon and are consistent with earlier studies. We confirm a correlation between the size of the radio structure and the radio luminosity. A comparison between Seyfert types 1 and 2 finds that type 2s tend to have a larger linear size. There is no statistically significant difference in radio power between types 1 and 2, although all the most powerful objects appear to be Seyfert 2's. No significant difference has been found in the spectral indices.

Key words: radio continuum: galaxies -- galaxies: Seyfert