DUST EMISSION FROM PROTOSTARS - THE DISK AND ENVELOPE OF HH-24-MMS

High-resolution imaging of the protostar HH 24 MMS at wavelengths of 7 mm and 3.4 mm shows the dust emission to originate from two component s: an unresolved disk and an extended envelope. The envelope is an ord er of magnitude more massive than the disk, suggesting that HH 24 MMS is very young, since the fraction of circumstellar material in an exte nded component probably decreases with the age of the forming star. Fo r the disk, the frequency dependence of the dust mass opacity coeffici ent, beta, is 0.68 +/- 0.12, significantly lower than the interstellar medium value of 2. In the envelope beta is less well constrained but must lie in the range 0 to 1.9. Emission from the disk dominates at wa velengths longer than 3 mm, but the far-infrared emission is relativel y weak. This suggests that the envelope is optically thick at waveleng ths as short as 60 mu m and obscures the disk.