Searching for O2 in the SMC: Academic Article uri icon

  • Overview
  • Research
  • Identity
  • Additional Document Info
  • View All


  • We present a 39 h integration with the Odin satellite on the ground-state 118.75 GHz line of O2 towards the region of strongest molecular emission in the Small Magellanic Cloud. Our 3sigma upper limit to the O2 integrated intensity of <0.049 K km/s in a 9'(160 pc) diameter beam corresponds to an upper limit on the O2/H2 abundance ratio of <1.3E-6. Although a factor of 20 above the best limit on the O2 abundance obtained for a Galactic source, our result has interesting implications for understanding oxygen chemistry at sub-solar metal abundances. We compare our abundance limit to a variety of astrochemical models and find that, at low metallicities, the low O2 abundance is most likely produced by the effects of photo-dissociation on molecular cloud structure. Freeze-out of molecules onto dust grains may also be consistent with the observed abundance limit, although such models have not yet been run at sub-solar initial metallicities.


  • Wilson, Christine D
  • Olofsson, AOH
  • Pagani, L
  • Booth, RS
  • Frisk, U
  • Hjalmarson, Å
  • Olberg, M
  • Sandqvist, Aa

publication date

  • April 2005