A Methyl Cyanide Search for the Earliest Stages of Massive Protostars

Abstract

Forty-eight candidate massive protostar regions were surveyed for methyl cyanide (CH3CN) emission using the Heinrich Hertz Telescope (HHT) on Mount Graham, AZ. CH3CN J = 12-11 emission at 220 GHz was detected toward 25 regions. Thirteen of these are new detections, yielding a substantial number of new candidates for massive protostars. The CH313CN (J = 12-11) isotopomer was included in the bandpass of all observed sources and was detected toward eight sources in our sample. These sources are probably optically thick in some of the CH3CN lines. CH3CN J = 25-24 emission at 460 GHz was detected in at least one K-component toward five of 11 sources observed in this transition. Using a rotational equilibrium temperature analysis we estimate the CH3CN rotation temperatures and beam-averaged column densities for 20 of the sources.