Results of the ESO-SEST Key Programme on CO in the Magellanic Clouds

X. CO emission from star formation regions in LMC and SMC

¹ Sterrewacht Leiden, PO Box 9513, 2300 RA Leiden, The Netherlands
² Onsala Space Observatory, 439-92 Onsala, Sweden
³ Departamento de Astronomia, Universidad de Chile, Casilla 36-D, Santiago, Chile
⁴ Laboratorium voor Ruimteonderzoek, SRON, Postbus 800, 9700 AV Groningen, The Netherlands
⁵ Radioastronomie, École Normale Supérieure, 24 rue Lhomond, 75231 Paris Cedex 05, France
⁶ Institut d'Astrophysique Spatiale, Bât. 120, Université de Paris-XI, 91045 Orsay Cedex, France
⁷ Astronomy Department, University of Texas at Austin, USA
⁸ LERMA, Observatoire de Paris, 61 Av. de l'Observatoire, 75014 Paris, France
⁹ European Southern Observatory, Casilla 19001, Santiago 19, Chile

Corresponding author: F. P. Israel, israel@strw.leidenuniv.nl

Received: 4 April 2003
Accepted: 12 May 2003

Abstract

We present and  maps of several star-forming regions in both the Large and the Small Magellanic Cloud, and briefly discuss their structure. Many of the detected molecular clouds are relatively isolated and quite small with dimensions of typically 20 pc. Some larger complexes have been detected, but in all cases the extent of the molecular clouds sampled by CO emission is significantly less than the extent of the ionized gas of the star-formation region. Very little diffuse extended CO emission was seen; diffuse CO in between or surrounding the detected discrete clouds is either very weak or absent. The majority of all LMC lines of sight detected in  has an isotopic emission ratio  of about 10, i.e. twice higher than found in Galactic star-forming complexes. At the lowest  intensities, the spread of isotopic emission ratios rapidly increases, low ratios representing relatively dense and cold molecular gas and high ratios marking CO photo-dissociation at cloud edges.