No CrossRef data available.
Published online by Cambridge University Press: 24 July 2012
Class I 44 GHz methanol masers are not as well-known, as common, or as bright as their more famous Class II cousins at 6.7 and 12.2 GHz. Nevertheless, the 44 GHz masers are commonly found in high-mass star forming regions. At times they appear to trace dynamically important phenomena; at other times they show no obvious link to the star formation process. Here, we summarize the major observational efforts to date, including both dedicated surveys and collateral observations. The principal results are presented, some that were expected, and others that were unexpected.