Free Access
Astron. Astrophys. Suppl. Ser.
Volume 141, Number 2, January II 2000
Page(s) 193 - 209
Published online 15 January 2000
DOI: 10.1051/aas:2000119

Astron. Astrophys. Suppl. Ser. 141, 193-209

Dense molecular gas in Seyfert galaxies[*]

S.J. Curran - S. Aalto - R.S. Booth

Send offprint request: S. Curran

1 - Onsala Space Observatory, Chalmers University of Technology, S-439 92 Onsala, Sweden

Received March 2; accepted October 22, 1999


We have used the 20 m Onsala and 15 m SEST telescopes to observe the CO  $J=1\rightarrow0$ (simultaneously with CO  $J=2\rightarrow1$ at SEST) and HCN   $J=1\rightarrow0$ (simultaneously with CS  $J=3\rightarrow2$ at SEST) transitions in 20 Seyfert galaxies. The sample consists of the 18 galaxies detected in CO  $J=1\rightarrow0$ by [Heckman et al. (1989)] plus 2 which were not detected in their survey. We have successfully detected all of the galaxies in the CO transition and 13 in HCN of which NGCs 1667, 2273, 5033, 5135, 6814 and Mrk 273 are new detections. For the galaxies in which the beam-width exceeds $\approx10$ kpc we find that $\frac{L_{\rm HCN}}{L_{\rm
CO}}\approx1/6$, i.e. a global ratio similar to that of ultra-luminous infrared galaxies and over 10 times the ratio for normal spiral galaxies. This implies that $\frac{L_{\rm
FIR}}{L_{\rm CO}}~(L_{\rm FIR}\sim10^{11}~L_{\odot}~{\rm
Seyferts})\approx10\frac{L_{\rm FIR}}{L_{\rm CO}}~({\rm normal
~spirals})$ and we believe that the far infrared fluxes in our sample arise from star-burst activity, although we cannot rule out the possibility of a contribution from active galactic nuclei.

Key words: galaxies: Seyfert-galaxies: abundances -- galaxies: ISM

SIMBAD Objects

Copyright The European Southern Observatory (ESO)

Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.

Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.

Initial download of the metrics may take a while.