Carbon monoxide in clouds at low metallicity in the dwarf irregular galaxy WLM

@article{Elmegreen2013CarbonMI,
  title={Carbon monoxide in clouds at low metallicity in the dwarf irregular galaxy WLM},
  author={Bruce G. Elmegreen and M{\'o}nica Rubio and Deidre A. Hunter and Celia Verdugo and Elias Brinks and Andreas Schruba},
  journal={Nature},
  year={2013},
  volume={495},
  pages={487-489}
}
Carbon monoxide (CO) is the primary tracer for interstellar clouds where stars form, but it has never been detected in galaxies in which the oxygen abundance relative to hydrogen is less than 20 per cent of that of the Sun, even though such ‘low-metallicity’ galaxies often form stars. This raises the question of whether stars can form in dense gas without molecules, cooling to the required near-zero temperatures by atomic transitions and dust radiation rather than by molecular line emission… 

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