Dense gas in nearby galaxies. I. Distribution, kinematics and multilevel studies of CS.

Maps in the J=2 - 1 transition of CS galaxies 1C 342 and NGC 253 are presented. The distribution of the CS emission from NGC 253 is consistent with the distribution of the CO 1 - 0 line. The CS emission from IC 342, however, resembles more that seen in the CO 3 - 2 transition. For the first time, the isotopic substitution C^34^S is reported from an external galaxy: The C^34^S 2 - 1 line has been detected toward NGC 253 and M 82 and the C^34^S 3 - 2 line has been detected tentatively toward M 82. Also for the first time, extragalactic CS has been observed in the 3 - 2 and 5 - 4 transitions toward NGC 253, 1C 342 and M 82. From this, the density of H-2_ in the CS emitting regions of NGC 253 is ~ 10^5.0+/-0.4^ cm^-3^;- toward IC 342, we obtain n(H_2_) <= 10^5.0^ cm^-3^. Toward M 82, there are regions with n(H_2_)~10^4^ and 10^5^ cm^-3^. Relative CS abundances are consistent with Galactic values.