The Circumstellar Environment of the Early B Protostar G192.16-3.84 and the Discovery of a Low-Mass, Protostellar Core

We have observed the massive star-forming region associated with the early B protostar G192.16-3.84 in NH3(1, 1), 22.2 GHz H2O masers, 1.3 cm continuum emission, and at 850 μm. The dense gas associated with G192.16 is clumpy, is optically thin, and has a mass of 0.9 M☉. The NH3 core is gravitationally unstable, which may signal that the outflow phase of this system is coming to an end. Water masers trace an ionized jet 0.″8 (1600 AU at a distance of 2 kpc) north of G192.16. Masers are also located within 500 AU of G192.16; their velocity distribution is consistent with but does not strongly support the interpretation that the maser emission arises in a 1000 AU rotating disk centered on G192.16. Roughly 30'' south of G192.16 (0.3 pc) is a compact, optically thick (τ = 1.2) NH3 core (called G192 S3) with an estimated mass of 2.6 M☉. Based on the presence of 850 μm and 1.2 mm continuum emission, G192 S3 probably harbors a very young, low-mass protostar or protocluster. The dense gas in the G192 S3 core is likely to be gravitationally bound and may represent the next site of star formation in this region.