An NH3 ring around the infrared sources in NGC 2071

The NGC 2071 star formation region was observed in the NH3 (1, 1) and (2, 2) lines using the VLA, equipped with new K band receivers. The main hyperfine component and one of the inner satellite hyperfine components of the (1, 1) transition and the main hyperfine component of the (2, 2) transition were detected. Most of the NH3 emission was found to arise from a ring structure with a 60 arcsec (24,000 AU) radius, centered on IRS 1-3. The gas has a temperature slightly below 20 K. A small amount of emission is seen close to IRS 1-3 (about 5 arcsec), arising from gas at a temperature of at least 32 K. The abundance of NH3 inside the ring is down by at least a factor of 10 from the value in the ring. The main body of the NH3 emission has no detectable velocity gradient, consistent with its being far from the central stars; the hotter NH3 emission has a velocity field consistent with Keplerian rotation around a 5-solar-mass object.