High spatial resolution isotopic CO and CS observations of M17 SW - The clumpy structure of the molecular cloud core

This paper presents high-angular-resolution maps of the M17 SW cloud core in the C(O-18) J = 2-1 (13 arcsec FWHM beam) and C(S-34) J = 2-1 (27 arcsec FWHM), 3-2 (17 arcsec FWHM) lines obtained with the IRAM 30 m telescope. These maps directly reveal the clumpy structure of the entire cloud core down to linear scales of 13 arcsec and below. Individual clumps have line widths as small as 0.5 km/s, compared to a line width of 3-5 km/s observed with lower angular resolution in the same lines. The C(O-18) 2-1 line reaches a peak brightness temperature of 24 K in the 13-arcsec beam and is probably slightly optically thick in several locations. Spectra in the more abundant CO isotopes obtained toward several selected positions show strong self-absorption notches and peak brightness temperatures in between these notches of about 100 K. 65 refs