1997/07/14 by C. D. Wilson, Christine D. Wilson · 1 citation
Physics and Astronomy · #Astrophysics and Star Formation Studies #Galaxies: Formation, Evolution, Phenomena #Superconducting and THz Device Technology #astro-ph
paper · pdf · doi:10.1086/310881
12 pages, aastex, 1 postscript figure; accepted for publication in ApJ Letters; also available at http://www.physics.mcmaster.ca/Wilson_Preprints/
arxiv created 1997/07/14 · openalex publication_date 1997/09/20 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/01
We present observations of the 492 GHz [C I] emission for four individual giant molecular clouds in the Local Group galaxy M33 obtained with the James Clerk Maxwell Telescope. The average [CI] to CO J = 1-0 integrated intensity ratio of 0.10 ± 0.03 is similar to what is observed in Galactic molecular clouds but is smaller than what is seen in starburst galaxies. Similarly, the column density ratio N (C)/ N (CO) is similar to that observed in the Orion Bar but is smaller than values obtained for starburst galaxies. The [CI] line is found to be a more important coolant than the lowest three rotational transitions of CO for all the clouds in the sample. The [CI] luminosity does not appear to be enhanced significantly in two low-metallicity clouds, which may be a result of the unusual ionization environment of the clouds.