44 GHZ CLASS I METHANOL (CH 3 OH) MASER SURVEY IN THE GALACTIC CENTER

Abstract

We report on a large 44 GHz (7 0 –6 1 A + ) methanol (CH 3 OH) maser survey of the Galactic Center. The Karl G. Jansky Very Large Array was used to search for CH 3 OH maser emission covering a large fraction of the region around Sgr A. In 25 pointings, over 300 CH 3 OH maser sources (>10 σ ) were detected. The majority of the maser sources have a single peak emission spectrum with line of sight velocities that range from about −13 to 72 km s −1 . Most maser sources were found to have velocities around 35−55 km s −1 , closely following velocities of neighboring interacting molecular clouds (MCs). The full width at half-maximum of each individual spectral feature is very narrow (∼0.85 km s −1 on average). In the north, where Sgr A East is known to be interacting with the 50 km s −1 MC, more than 100 44 GHz CH 3 OH masers were detected. In addition, three other distinct concentrations of masers were found, which appear to be located closer to the interior of the interacting MCs. It is possible that a subset of masers is associated with star formation, although conclusive evidence is lacking.