Black hole accretion and star formation as drivers of gas excitation and chemistry in Mrk231

• Published in: arXiv.org 2010-05
• Main Authors: P P Van der Werf, 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, Gonzalez-Alfonso, E, Naylor, D, Aalto, S, Charmandaris, V, Dasyra, K M, Evans, A, Gao, Y, Greve, T R, Guesten, R, Kramer, C, Martin-Pintado, J, Mazzarella, J, Papadopoulos, P P, Sanders, D B, Spinoglio, L, Stacey, G, Vlahakis, C, Wiedner, M C, Xilouris, E M
• Format: Article
• Language: English
• Subjects: Active galactic nuclei; Clumps; Deposition; Excitation; Galaxies; Infrared astronomy; Luminosity; Organic chemistry; Star & galaxy formation; Star formation; Supermassive black holes; Ultraviolet radiation; X-rays
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1005.2877

We present a full high resolution SPIRE FTS spectrum of the nearby ultraluminous infrared galaxy Mrk231. 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 Mrk231 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 Mrk231. 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 Mrk231 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 Mrk231. The extraordinary luminosity of the OH+ and H2O+ lines reveals the signature of X-ray driven excitation and chemistry in this region.