Volume 533, September 2011
|Number of page(s)||4|
|Published online||30 August 2011|
Letter to the Editor
Turbulent and fast motions of H2 gas in active galactic nuclei
Laboratoire AIM, CEA/DSM-CNRS-Université Paris Diderot, Irfu/Service d’Astrophysique, CEA Saclay, 91191 Gif-sur-Yvette, France
2 Observatoire de Paris, LERMA (CNRS:UMR 8112), 61 Av. de l’Observatoire, 75014 Paris, France
Received: 19 July 2011
Accepted: 13 August 2011
Querying the Spitzer archive for optically-selected active galactic nuclei (AGN) observed in high-resolution-mode spectroscopy, we identified radio and/or interacting galaxies with highly turbulent motions of H2 gas at a temperature of a few hundred Kelvin. Unlike all other AGN that have unresolved H2 line profiles at a spectral resolution of ~600, 3C 236, 3C 293, IRAS 09039+0503, MCG-2-58-22 and Mrk 463E have intrinsic velocity dispersions exceeding 200 km s-1 for at least two of the rotational S0, S1, S2, and S3 lines. In a sixth source, 4C 12.50, a blue wing was detected in the S1 and S2 line profiles, indicating the presence of a warm molecular gas component moving at − 640 km s-1 with respect to the bulk of the gas at systemic velocity. Its mass is 5.2 × 107 M⊙, accounting for more than one fourth of the H2 gas at 374 K, but less than 1% of the cold H2 gas computed from CO observations. Because no diffuse gas component of 4C 12.50 has been observed to date to be moving at more than 250 km s-1 from systemic velocity, the H2 line wings are unlikely to be tracing gas in shock regions along the tidal tails of this merging system. They can instead be tracing gas driven by a jet or entrained by a nuclear outflow, which is known to emerge from the west nucleus of 4C 12.50. It is improbable that such an outflow, with an estimated mass loss rate of 130 M⊙ yr-1, entirely quenches the star formation around this nucleus.
Key words: ISM: jets and outflows / galaxies: active / infrared: galaxies / line: profiles / ISM: kinematics and dynamics / galaxies: nuclei
© ESO, 2011
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