2007/06/11 by T. Tosaki, Tomoka Tosaki, R. Miura +11 · 2 citations
Physics and Astronomy · #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Star Formation Studies #Axial ratio #Galaxies: Formation, Evolution, Phenomena #Galaxy #Optics #Physics #Spiral galaxy #Star cluster #Star formation #Stars #Supergiant #Supernova #astro-ph
paper · pdf · doi:10.1086/520624
published as Astrophys.J.664:L27-LL30, 2007 · 4 pages, 4 figures. The Astrophysical Journal Letters, in press
arxiv created 2007/06/11 · openalex publication_date 2007/07/09 · arxiv updated 2011/06/21 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We report the discovery of a high CO ( J = 3-2)/CO ( J = 1-0) ratio gas with an arclike distribution ("high-ratio gas arc") surrounding the central star cluster of the supergiant H II region NGC 604 in the nearby spiral galaxy M33, based on multi- J CO observations of a 5' × 5' region of NGC 604 conducted using the ASTE 10 m and NRO 45 m telescopes. The discovered "high-ratio gas arc" extends to the southeast-northwest direction with a size of ~200 pc. The western part of the high-ratio gas arc closely coincides with the shells of the H II regions traced by Hα and radio continuum peaks. The CO ( J = 3-2)/CO ( J = 1-0) ratio, R 3-2/1-0 , ranges between 0.3 and 1.2 in the observed region, and the R 3-2/1-0 values of the high-ratio gas arc are around or higher than unity, indicating very warm ( T kin ≥ 60 K) and dense ( n ≥ 10 3 -10 4 cm -3 ) conditions of the high-ratio gas arc. We suggest that the dense gas formation and second-generation star formation occur in the surrounding gas compressed by the stellar wind and/or supernova of the first-generation stars of NGC 604, i.e., the central star cluster of NGC 604.