An Embedded Active Nucleus in the OH Megamaser Galaxy IRAS16399−0937

Authors

Dinalva A. Sales, Universidade Federal do Rio Grande do Sul, Brazil
A. Robinson, Rochester Institute of Technology
D. J. Axon, Rochester Institute of Technology
J. Gallimore, Bucknell University
P. Kharb, Indian Institute of Astrophysics, India
R. L. Curran, Rochester Institute of Technology
C. O'Dea, Rochester Institute of Technology
S. Baum, Rochester Institute of Technology
Moshe Elitzur, University of KentuckyFollow
R. Mittal, Rochester Institute of Technology

Abstract

We present a multiwavelength study of the OH megamaser galaxy IRAS16399–0937, based on new Hubble Space Telescope (HST)/Advanced Camera for Surveys F814W and Hα+[N II] images and archive data from HST, Two Micron All Sky Survey, Spitzer, Herschel and the Very Large Array. This system has a double nucleus, whose northern (IRAS16399N) and southern (IRAS16399S) components have a projected separation of ~6'' (3.4 kpc) and have previously been identified based on optical spectra as a low ionization nuclear emission line region (LINER) and starburst nucleus, respectively. The nuclei are embedded in a tidally distorted common envelope, in which star formation is mostly heavily obscured. The infrared spectrum is dominated by strong polycyclic aromatic hydrocarbon, but deep silicate and molecular absorption features are also present, and are strongest in the IRAS16399N nucleus. The 0.435-500 μm spectral energy distribution was fitted with a model including stellar, interstellar medium and active galactic nucleus (AGN) torus components using our new Markov Chain Monte Carlo code, CLUMPYDREAM. The results indicate that the IRAS16399N contains an AGN (L _bol ~ 10⁴⁴ erg s^–1) deeply embedded in a quasi-spherical distribution of optically thick clumps with a covering fraction ≈1. We suggest that these clumps are the source of the OHM emission in IRAS16399–0937. The high torus covering fraction precludes AGN photoionization as the origin of the LINER spectrum, however, the spectrum is consistent with shocks (v ~ 100-200 km s^–1). We infer that the ~10⁸ M _☉ black hole in IRAS16399N is accreting at a small fraction (~1%) of its Eddington rate. The low accretion rate and modest nuclear star formation rates suggest that while the gas-rich major merger forming the IRAS16399–0937 system has triggered widespread star formation, the massive gas inflows expected from merger simulations have not yet fully developed.

Document Type

Article

Publication Date

1-13-2015

Notes/Citation Information

Published in The Astrophysical Journal, v. 799, no. 1, 25, p. 1-28.

© 2015. The American Astronomical Society. All rights reserved.

The copyright holder has granted the permission for posting the article here.

Digital Object Identifier (DOI)

https://doi.org/10.1088/0004-637X/799/1/25

Funding Information

Support for program 11604 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. This material is based upon work partly supported by the National Aeronautics and Space Administration under grant No. NNX11AI03G issued through the Science Mission Directorate. D. A. Sales gratefully acknowledge for partial financial support received from FAPERGS/CAPES n.05/2013.

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Repository Citation

Sales, Dinalva A.; Robinson, A.; Axon, D. J.; Gallimore, J.; Kharb, P.; Curran, R. L.; O'Dea, C.; Baum, S.; Elitzur, Moshe; and Mittal, R., "An Embedded Active Nucleus in the OH Megamaser Galaxy IRAS16399−0937" (2015). Physics and Astronomy Faculty Publications. 260.
https://uknowledge.uky.edu/physastron_facpub/260