A Methyl Cyanide Search for the Earliest Stages of Massive Protostars

Forty-eight candidate massive protostar regions were surveyed for methyl cyanide (CH 3 CN) emission using the Heinrich Hertz Telescope (HHT) on Mount Graham, AZ. CH 3 CN 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 CH 3 13 CN ( 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 CH 3 CN lines. CH 3 CN 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 CH 3 CN rotation temperatures and beam-averaged column densities for 20 of the sources.