Submillimeter continuum observations of Rho Ophiuchi A - The candidate protostar VLA 1623 and prestellar clumps

Submillimeter continuum mapping of the Rho Ophiuchi A cloud core reveals four compact clumps with masses less than about 1 solar mass embedded in an arcshaped ridge of total mass about 15 solar, lying at the edge of the compact H II region around the B3 star S1. Three of the clumps appear amorphous in shape and are probably prestellar in nature. The fourth clump is the best defined and coldest and coincides with the young stellar object (YSO) VLA 1623. It is suggested that this object is a protostar whose circumstellar material is distributed in a 'cored-apple' envelope. The density gradient appears to be that of a centrally heated envelope or of an isothermal envelope with no central heating object. The mass ejection of VLA 1623 appears to be extremely efficient and implies that a global MHD approach to infall and outflow may be required to explain the youngest embedded sources. It is suggested that VLA 1623 and a few other low-luminosity YSOs make up an entirely new class of YSOs.