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 Bprotostar G192.16-3.84 in NH3(1,1), 22.2 GHz water masers, 1.3 cm continuumemission, and at 850 microns. The dense gas associated with G192.16 is clumpy,optically thin, and has a mass of 0.9 Msun. The ammonia core is gravitationallyunstable which may signal that the outflow phase of this system is coming to anend. 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, theirvelocity distribution is consistent with but does not strongly support theinterpretation that the maser emission arises in a 1000 AU rotating diskcentered on G192.16. Roughly 30" south of G192.16 (0.3 pc) is a compact,optically thick (optical depth = 1.2) ammonia core (called G192 S3) with anestimated mass of 2.6 Msun. Based on the presence of 850 micron and 1.2 mmcontinuum emission, G192 S3 probably harbors a very young, low-mass protostaror proto-cluster. The dense gas in the G192 S3 core is likely to begravitationally bound and may represent the next site of star formation in thisregion.