Determination of molecular gas properties using methyl cyanide lines

A survey has been made of 27 Galactic star-forming regions in the (CH3CN) 6 (K)-5(K), 5(K)-4(K), and 8(K)-7(K) lines of methyl cyanide (CH3CN) at 110, 92, and 147 GHz. Twenty-five sources were detected at 110 GHz, nineteen at 92 GHz, and three at 147 GHz. The strongest CH3CN emission arises in hot co res in regions of massive star formation. The abundance of CH3CN in these o bjects exceeds 10(-9) as a consequence of grain mantle evaporation. Weaker CH3CN lines were found in a number of sources. These can arise in either wa rm (30-50 K), dense (>10(4) cm(-3)) clouds or in hot regions with cooler ga s. (C) 2000 MAIK "Nauka/Interperiodica".