Black hole feeding and star formation in NGC 1808
Journal article, 2021
We report on Atacama Large Millimeter Array (ALMA) observations of CO(3-2) emission in the Seyfert2/starburst galaxy NGC1808, at a spatial resolution of 4 pc. Our aim is to investigate the morphology and dynamics of the gas inside the central 0.5 kpc and to probe the nuclear feeding and feedback phenomena. We discovered a nuclear spiral of radius 100 = 45 pc. Within it, we found a decoupled circumnuclear disk or molecular torus of a radius of 0:1300 = 6 pc. The HCN(4-3) and HCO+(4-3) and CS(7-6) dense gas line tracers were simultaneously mapped and detected in the nuclear spiral and they present the same misalignment in the molecular torus. At the nucleus, the HCN/HCO+ and HCN/CS ratios indicate the presence of an active galactic nucleus (AGN). The molecular gas shows regular rotation, within a radius of 400 pc, except for the misaligned disk inside the nuclear spiral arms. The computations of the torques exerted on the gas by the barred stellar potential reveal that the gas within a radius of 100 pc is feeding the nucleus on a timescale of five rotations or on an average timescale of 60 Myr. Some non-circular motions are observed towards the center, corresponding to the nuclear spiral arms. We cannot rule out that small extra kinematic perturbations could be interpreted as a weak outflow attributed to AGN feedback. The molecular outflow detected at 250 pc in the NE direction is likely due to supernovae feedback and it is connected to the kpc-scale superwind.
Galaxies: kinematics and dynamics
Galaxies: nuclei
Galaxies: ISM
Galaxies: starburst
Galaxies: individual: NGC 1808
Galaxies: active
Author
A. Audibert
Paris Observatory
Instituto de Astrofísica de Canarias
National Observatory of Athens
University of La Laguna
F. Combes
Collège de France
Paris Observatory
S. G. Burillo
Spanish National Observatory (OAN)
L. K. Hunt
Arcetri Astrophysical Observatory
A. Eckart
University of Cologne
Susanne Aalto
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
V. Casasola
Istituto di Radioastronomia
F. Boone
Institut de Recherche en Astrophysique et Planétologie (IRAP)
M. Krips
Institut de Radioastronomie Millimétrique (IRAM)
Serena Viti
University College London (UCL)
Leiden University
Sebastien Muller
Chalmers, Space, Earth and Environment, Onsala Space Observatory
K. M. Dasyra
National Observatory of Athens
University of Athens
P. van der Werf
Leiden University
S. Martin
European Southern Observatory Santiago
Atacama Large Millimeter-submillimeter Array (ALMA)
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 656 A60Subject Categories
Astronomy, Astrophysics and Cosmology
Atom and Molecular Physics and Optics
Fusion, Plasma and Space Physics
DOI
10.1051/0004-6361/202039886