Astron. Astrophys. 357, 1001-1012 (2000)

The -Orionis Ring in CO

W.J. Lang ¹, M.R.W. Masheder ¹, T.M. Dame ² and P. Thaddeus <sup>2

1</sup> H.H. Wills Physics Laboratory, Bristol University, Bristol, BS8 1TL. UK
² Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138, USA

Received 2 June 1999 / Accepted 18 February 2000

Abstract

The results of a new CO(J=10) survey of the ring of molecular clouds around the H II region Sh-2-264 and the -Orionis OB-association are presented. The distribution of molecular gas closely approximates that of the dust seen in IRAS emission. The total molecular mass is 1.410⁴ . The mass spectrum of the emission clumps is a power-law with index -1.8, similar to that observed in other star-forming regions. The kinematics of the ring are modelled, but its alignment close to the plane of the sky allows only very weak constraints on expansion velocity and the age of the system. The data are compared with previous surveys, and possible evolutionary schemes for the region discussed.

Key words: ISM: clouds Galaxy: structure radio lines: ISM ISM: molecules ISM: bubbles

Send offprint requests to: M.R.W. Masheder (Mike.Masheder@bristol.ac.uk)

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Contents

• 1. Introduction
• 2. Observations
• 3. Results
  • 3.1. The maps
  • 3.2. Mass estimates
• 4. Objects of interest
  • 4.1. B30
  • 4.2. The B35 Outflow
  • 4.3. The Northern and Southwestern Ring regions
  • 4.4. The L1598/1599 complex
  • 4.5. B223
• 5. Comparison with 100 µm emission
• 6. The distribution of young stars
  • 6.1. H emission stars
  • 6.2. IRAS point sources
• 7. Modelling of kinematics
• 8. Discussion
• 9. Conclusions
• Acknowledgements
• References

© European Southern Observatory (ESO) 2000

Online publication: June 5, 2000
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