Resolving the Bright HCN(1-0) Emission toward the Seyfert 2 Nucleus of M51: Shock Enhancement by Radio Jets and Weak Masing by Infrared Pumping?
Artikel i vetenskaplig tidskrift, 2015

We present high angular resolution observations of the HCN(1-0) emission (at ~1'' or ~34 pc), together with CO J = 1-0, 2-1, and 3-2 observations, toward the Seyfert 2 nucleus of M51 (NGC 5194). The overall HCN(1-0) distribution and kinematics are very similar to that of the CO lines, which have been indicated as the jet-entrained molecular gas in our past observations. In addition, high HCN(1-0)/CO(1-0) brightness temperature ratio of about unity is observed along the jets, similar to that observed at the shocked molecular gas in our Galaxy. These results strongly indicate that both diffuse and dense gases are entrained by the jets and outflowing from the active galactic nucleus. The channel map of HCN(1-0) at the systemic velocity shows a strong emission right at the nucleus, where no obvious emission has been detected in the CO lines. The HCN(1-0)/CO(1-0) brightness temperature ratio at this region reaches >2, a value that cannot be explained considering standard physical/chemical conditions. Based on our calculations, we suggest infrared pumping and possibly weak HCN masing, but still requiring an enhanced HCN abundance for the cause of this high ratio. This suggests the presence of a compact dense obscuring molecular gas in front of the nucleus of M51, which remains unresolved at our ~1'' (~34 pc) resolution, and consistent with the Seyfert 2 classification picture.

galaxies: individual (M51

ISM: jets and outflows

galaxies: jets

galaxies: nuclei

galaxies: Seyfert

galaxies: ISM

NGC 5194)


S Matsushita

Academia Sinica

Dinh-V Trung

Vietnam Academy of Science and Technology

F. Boone

Centre national de la recherche scientifique (CNRS)

Université de Toulouse

M. Krips

Institut de Radioastronomie Millimétrique (IRAM)

J. Lim

The University of Hong Kong

Sebastien Muller

Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium

Astrophysical Journal

0004-637X (ISSN) 1538-4357 (eISSN)

Vol. 799 1 26- 26


Astronomi, astrofysik och kosmologi



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