Thick discs, and an outflow, of dense gas in the nuclei of nearby Seyfert galaxies

Ming Yi Lin, R. I. Davies, L. Burtscher, A. Contursi, R. Genzel, E. González-Alfonso, J. Graciá-Carpio, A. Janssen, D. Lutz, G. Orban de Xivry, D. Rosario, A. Schnorr-Müller, A. Sternberg, E. Sturm, L. Tacconi

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

We discuss the dense molecular gas in central regions of nearby Seyfert galaxies, and report new arcsec resolution observations of HCN (1-0) and HCO+ (1-0) for three objects. In NGC 3079, the lines show complex profiles as a result of self-absorption and saturated continuum absorption. H13CN reveals the continuum absorption profile, with a peak close to the galaxy's systemic velocity that traces disc rotation, and a second feature with a blue wing extending to -350 km s-1 that most likely traces a nuclear outflow. The morphological and spectral properties of the emission lines allow us to constrain the dense gas dynamics. We combine our kinematic analysis for these three objects, as well as another with archival data, with a previous comparable analysis of four other objects, to create a sample of eight Seyferts. In seven of these, the emission line kinematics imply thick disc structures on radial scales of ~100 pc, suggesting such structures are a common occurrence. We find a relation between the circum-nuclear LHCN and Mdyn that can be explained by a gas fraction of 10 per cent and a conversion factor αHCN ~ 10 between gas mass and HCN luminosity. Finally, adopting a different perspective to probe the physical properties of the gas around active galactic nuclei, we report on an analysis of molecular line ratios which indicates that the clouds in this region are not self-gravitating.

Original languageEnglish
Pages (from-to)1375-1392
Number of pages18
JournalMonthly Notices of the Royal Astronomical Society
Volume458
Issue number2
DOIs
StatePublished - 2 Mar 2016

Keywords

  • Galaxies: Active
  • Galaxies: ISM
  • Galaxies: Nuclei
  • Galaxies: Seyfert
  • Submillimetre: Galaxies

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