Torsionally excited methanol in hot molecular cloud cores

Torsionally excited methanol lines were detected in the direction of four galactic molecular cloud regions by means of scans in the 20-24 GHz interval with the Effelsberg 100 m radiotelescope. Transitions in both the first torsionally excited state, with excitation energies of about 450 K, and the ground state were seen in the direction of the hot, molecular cloud cores of the Orion-KL region, W3(OH), NGC 7538 and W51. The emission in Orion originated from a hot region in the southern ridge cloud 4 arcsec from the hot core. The greatest deviations from LTE occurred when a strong compact continuum source was present.