DUST EMISSION FROM STAR-FORMING REGIONS .4. DENSE CORES IN THE ORION-B MOLECULAR CLOUD

In a search for isothermal pre-stellar cores and protostars we surveye d with SEST and IRAM MRT part of the Orion B GMC for its lambda 1.3 mm dust emission. We used the CS(2-1) survey by Lada et al. (1991a; LBS) as a search list. We determine the morphology of the detected cloud c ores with angular resolutions of 23 '' (SEST) and 12 '', respectively. About one half of these cores have a compact core surrounded by an ex tended envelope. The lambda 1.3 mm dust emission maps were compared wi th NIR (2.13 mu m) and FIR (IRAS) maps to discriminate between isother mal and self-luminous cores. About one half of the cores were classifi ed as isothermal. A comparison of virial masses derived from CS line w idths with gas masses derived from lambda 1.3 mm dust emission shows t hat virial masses are on average by a factor of 20 ... 30 larger. This can be explained by line opacity and by the larger beamwidths (1.8' v s. 23 '' and 1 '''', respectively) of the CS survey.