A COMPREHENSIVE SEARCH FOR EXTRAGALACTIC 6.7-GHZ METHANOL MASERS

We have used the Australia Telescope Compact Array (ATCA) to search fo r 6.7-GHz methanol maser emission towards 87 galaxies. We chose the ta rget sources using several criteria, including far-IR luminosities and the presence of known OH megamasers. In addition, we searched for met hanol masers in the nearby starburst galaxy NGC 253, making a full spe ctral line synthesis image, No emission was detected in any of the gal axies, with detection limits ranging from 25 to 75 mJy. This is surpri sing, given the close association of OH and methanol masers in Galacti c star formation regions, and significantly constrains models of OH me gamaser emission. This absence of maser emission may be a result of lo w methanol abundances in molecular clouds in starburst galaxies.