Molecular gas properties of 12-μm Seyfert galaxies - I. The southern sample

Abstract

We have used the 15-m Swedish European Southern Observatory (ESO) Submillimetre Telescope (SEST) to observe the J = 1 → 0 and J = 2 → 1 transition lines of CO in 30 Southern hemisphere Seyfert galaxies from the extended 12-μm sample of Rush, Malkan & Spinoglio. We detected CO J = 1 → 0 in 16 out of the 30 Seyfert galaxies and CO J = 2 → 1 in 17 out of the 30 Seyfert galaxies. From the observed spectra, various CO gas properties have been derived including the luminosity of the CO gas and, using a standard conversion factor, the H 2 mass. The average H 2 gas mass for Seyfert 1 galaxies was 3 x 10 9 M ○. for CO J = 1 → 0 and 1 x 10 9 M ○. for CO J = 2 → 1, while in comparison the H 2 gas mass for Seyfert 2 type galaxies was 11 x 10 9 M ○. for CO J = 1 → 0 and 3 x 10 9 M ○. CO J = 2 → 1. From this small sample of Seyfert galaxies, we tentatively support the conclusion that type 2 Seyfert galaxies contain more molecular gas than their type 1 counterparts.