Molecular and Atomic Gas in the Large Magellanic Cloud. II. Three-dimensional Correlation Between CO and H I

Creators: Fukui, Y.; Kawamura, A.; Wong, T.; Murai, M.; Iritani, H.; Mizuno, N.; Mizuno, Y.; Onishi, T.; Hughes, A.; Ott, J.; Muller, E.; Staveley-Smith, L.; Kim, S.

Abstract

We compare the CO (J = 1-0) and H I emission in the Large Magellanic Cloud in three dimensions, i.e., including a velocity axis in addition to the two spatial axes, with the aim of elucidating the physical connection between giant molecular clouds (GMCs) and their surrounding H I gas. The CO J = 1-0 data set is from the second NANTEN CO survey and the H I data set is from the merged Australia Telescope Compact Array (ATCA) and Parkes Telescope surveys. The major findings of our analysis are as follows: (1) GMCs are associated with an envelope of H I emission, (2) in GMCs [average CO intensity] ∝ [average H I intensity]^(1.1±0.1), and (3) the H I intensity tends to increase with the star formation activity within GMCs, from Type I to Type III. An analysis of the H I envelopes associated with GMCs shows that their average line width is 14 km s^(–1) and the mean density in the envelope is 10 cm^(–3). We argue that the H I envelopes are gravitationally bound by GMCs. These findings are consistent with a continual increase in the mass of GMCs via H I accretion at an accretion rate of 0.05 M_⊙ yr^(–1) over a timescale of 10 Myr. The growth of GMCs is terminated via dissipative ionization and/or stellar-wind disruption in the final stage of GMC evolution.

Additional Information

© 2009 The American Astronomical Society. Received 2008 December 19; accepted 2009 September 3; published 2009 October 8. The NANTEN project is based on a mutual agreement between Nagoya University and the Carnegie Institution of Washington (CIW). We greatly appreciate the hospitality of all the staff members of the Las Campanas Observatory of CIW. We are thankful to the many Japanese public donors and companies who contributed to the realization of the project. This study has made use of SIMBAD Astronomical Database and NASA's Astrophysics Data System Bibliographic Services. This work is financially supported in part by a Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology of Japan (No. 15071203), from JSPS (No. 14102003, No. 18684003, No. 20244014, and core-tocore program 17004). N.M. acknowledges the support of the Sumitomo Foundation, and T.O. of the Mitsubishi Foundation.

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