Astrophys. J., 664, L27-L30 (2007/July-3)
Arclike distribution of high CO (J=3-2)/CO (J=1-0) ratio gas surrounding the central star cluster of the supergiant H II region NGC 604.
TOSAKI T., MIURA R., SAWADA T., KUNO N., NAKANISHI K., KOHNO K., OKUMURA S.K. and KAWABE R.
Abstract (from CDS):
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'x5' 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, R3–2/1–0, ranges between 0.3 and 1.2 in the observed region, and the R3–2/1–0 values of the high-ratio gas arc are around or higher than unity, indicating very warm (Tkin≥60 K) and dense (nH2≥103-104 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.
Galaxies: Individual: Messier Number: M33 - ISM: H II Regions - ISM: Individual: NGC Number: NGC 604 - ISM: Molecules - Stars: Formation
Status at CDS:
Parag. 4.1 : Cloud NGC 604-2 = [WS92] NGC 604-2
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