Black hole accretion and star formation as drivers of gas excitation and chemistry in Markarian 231

July 2010 • 2010A&A...518L..42V

Authors • van der Werf, P. P. • Isaak, K. G. • Meijerink, R. • Spaans, M. • Rykala, A. • Fulton, T. • Loenen, A. F. • Walter, F. • Weiß, A. • Armus, L. • Fischer, J. • Israel, F. P. • Harris, A. I. • Veilleux, S. • Henkel, C. • Savini, G. • Lord, S. • Smith, H. A. • González-Alfonso, E. • Naylor, D. • Aalto, S. • Charmandaris, V. • Dasyra, K. M. • Evans, A. • Gao, Y. • Greve, T. R. • Güsten, R. • Kramer, C. • Martín-Pintado, J. • Mazzarella, J. • Papadopoulos, P. P. • Sanders, D. B. • Spinoglio, L. • Stacey, G. • Vlahakis, C. • Wiedner, M. C. • Xilouris, E. M.

Abstract • We present a full high resolution SPIRE FTS spectrum of the nearby ultraluminous infrared galaxy Mrk 231. In total 25 lines are detected, including CO J = 5-4 through J = 13-12, 7 rotational lines of H₂O, 3 of OH⁺ and one line each of H₂O⁺, CH⁺, and HF. We find that the excitation of the CO rotational levels up to J = 8 can be accounted for by UV radiation from star formation. However, the approximately flat luminosity distribution of the CO lines over the rotational ladder above J = 8 requires the presence of a separate source of excitation for the highest CO lines. We explore X-ray heating by the accreting supermassive black hole in Mrk 231 as a source of excitation for these lines, and find that it can reproduce the observed luminosities. We also consider a model with dense gas in a strong UV radiation field to produce the highest CO lines, but find that this model strongly overpredicts the hot dust mass in Mrk 231. Our favoured model consists of a star forming disk of radius 560 pc, containing clumps of dense gas exposed to strong UV radiation, dominating the emission of CO lines up to J = 8. X-rays from the accreting supermassive black hole in Mrk 231 dominate the excitation and chemistry of the inner disk out to a radius of 160 pc, consistent with the X-ray power of the AGN in Mrk 231. The extraordinary luminosity of the OH⁺ and H₂O⁺ lines reveals the signature of X-ray driven excitation and chemistry in this region.

Links

• PREPRINT http://arxiv.org/abs/1005.2877
• NED https://ned.ipac.caltech.edu/uri/NED::InRefcode/2010A%26A...518L..42V
• POSTSCRIPT https://www.aanda.org/10.1051/0004-6361/201014682/postscript
• ELECTR https://doi.org/10.1051%2F0004-6361%2F201014682
• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2010A%26A...518L..42V
• PDF https://www.aanda.org/10.1051/0004-6361/201014682/pdf
• DATA http://archives.esac.esa.int/hsa/whsa/?ACTION=PUBLICATION&ID=2010A%26A...518L..42V