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

P. P. van der Werf ; K. G. Isaak ; R. Meijerink ; M. Spaans ; A. Rykala ; T. Fulton ; A. F. Loenen ; F. Walter ; A. Weiss ; L. Armus ; J. Fischer ; F. P. Israel ; A. I. Harris ; S. Veilleux ; C. Henkel ; G. Savini ; S. Lord ; H. A. Smith ; E. Gonzalez-Alfonso ; D. Naylor ; Susanne Aalto (Institutionen för rymd- och geovetenskap, Radioastronomi och astrofysik) ; V. Charmandaris ; K. M. Dasyra ; A. Evans ; Y. Gao ; T. R. Greve ; R. Gusten ; C. Kramer ; J. Martin-Pintado ; J. Mazzarella ; P. P. Papadopoulos ; D. B. Sanders ; L. Spinoglio ; G. Stacey ; C. Vlahakis ; M. C. Wiedner ; E. M. Xilouris
Astronomy & Astrophysics (0004-6361). Vol. 518 (2010), Article Number: L42 ,
[Artikel, refereegranskad vetenskaplig]

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.

Nyckelord: galaxies: individual: Mrk 231, galaxies: active, galaxies: ISM, galaxies: nuclei, galaxies: starburst, infrared: galaxies, galaxy nuclei, dense gas, diagnostics, emission, lines



Denna post skapades 2010-12-02. Senast ändrad 2014-09-02.
CPL Pubid: 129975

 

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