2005/09/16 by F. P. Israel, R. P. J. Tilanus, F. Baas · 3 citations
Chemistry · Physics and Astronomy · #Astrophysics and Star Formation Studies #Molecular Spectroscopy and Structure #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1051/0004-6361:20053096
Accepted for publication by A&A
arxiv created 2005/09/16 · openalex publication_date 2006/01/01 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/04
We present , , maps as well as , and 492 GHz [CI] measurements of the central region in M 51. The distribution of CO is strongly concentrated towards the spiral arms. The center itself is poor in, though not devoid of, CO emission. The observed line intensities require modelling with a multi-component molecular gas. A dense component must be present () with kinetic temperature 100 K, combined with either a less dense () component of the same temperature, or a more dense () and much cooler (Tkin = 10–30 K) component. Atomic carbon amounts are between 5 and 10 times those of CO. Much of the molecular gas mass is associated with the hot PDR phase. The center of M 51 has a face-on gas mass density of about pc-2, and a well-established CO-to-H2 conversion ratio X four to five times lower than the standard Galactic value.