The Dense Molecular Gas and Nuclear Activity in the ULIRG IRAS 13120-5453
Journal article, 2017
We present new Atacama Large Millimeter/submillimeter Array Band 7 (?340 GHz) observations of the dense gas tracers HCN, HCO+, and CS in the local, single-nucleus, ultraluminous infrared galaxy IRAS 13120-5453. We find centrally enhanced HCN (4-3) emission, relative to HCO+ (4-3), but do not find evidence for radiative pumping of HCN. Considering the size of the starburst (0.5 kpc) and the estimated supernovae rate of ?1.2 yr-1, the high HCN/HCO+ ratio can be explained by an enhanced HCN abundance as a result of mechanical heating by the supernovae, though the active galactic nucleus and winds may also contribute additional mechanical heating. The starburst size implies a high ?IR of 4.7 × 1012 L? kpc-2, slightly below predictions of radiation-pressure limited starbursts. The HCN line profile has low-level wings, which we tentatively interpret as evidence for outflowing dense molecular gas. However, the dense molecular outflow seen in the HCN line wings is unlikely to escape the Galaxy and is destined to return to the nucleus and fuel future star formation. We also present modeling of Herschel observations of the H2O lines and find a nuclear dust temperature of ?40 K. IRAS 13120-5453 has a lower dust temperature and ?IR than is inferred for the systems termed "compact obscured nuclei (CONs)" (such as Arp 220 and Mrk 231). If IRAS 13120-5453 has undergone a CON phase, we are likely witnessing it at a time when the feedback has already inflated the nuclear ISM and diluted star formation in the starburst/active galactic nucleus core.
galaxies: interactions
galaxies: individual (IRAS 13120-5453)
galaxies: ISM
galaxies: starburst
galaxies: active
Author
G. Privon
Pontificia Universidad Catolica de Chile
University of Concepcion
Susanne Aalto
Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics
Niklas Falstad
Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics
Sebastien Muller
Chalmers, Earth and Space Sciences, Onsala Space Observatory
E. Gonzalez-Alfonso
University of Alcalá
Kazimierz Sliwa
Max Planck Society
E. Treister
Pontificia Universidad Catolica de Chile
University of Concepcion
Francesco Costagliola
Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics
L. Armus
Spitzer Science Center
A. S. Evans
University of Virginia
National Radio Astronomy Observatory
S. G. Burillo
Spanish National Observatory (OAN)
T. Izumi
University of Tokyo
K. Sakamoto
Academia Sinica
P. van der Werf
Leiden University
J. Chu
University of Hawaii
Astrophysical Journal
0004-637X (ISSN) 1538-4357 (eISSN)
Vol. 835 2 Article Number: 213- 213Subject Categories
Astronomy, Astrophysics and Cosmology
DOI
10.3847/1538-4357/835/2/213