Observations of star-forming regions in the lines of methyl acetylene

The results of a survey of Galactic star-forming regions in the 5(K) - 4(K) and 6(K) - 5(K) methyl acetylene lines at 84.5 and 102.5 GHz are presented. Forty-three sources are found at 102.5 GHz and 23 at 84.5 GHz, respectively. The emission arise in warm clouds with the kinetic temperature 20-60 K and CH3CCH abundance about several units x 10(-9). Maximum entropy maps of NGC 2264, G30.8-0.1, G34.26+0.15, DR 21(OH), and S 140 demonstrate that the CH3CCH sources are roughly coincident with the areas of (CO)-C-13 and (CO)-O-18 emission. The sizes of the mapped clouds are enclosed in the range 0.1-1.7 pc, virial masses vary between 90 and 6200 M., and densities vary between 6 x 10(4) and 6 x 10(5) cm(-3).