A NEAR-INFRARED STUDY OF THE MONOCEROS R2 STAR-FORMATION REGION

We present H (1.65 mu m), K (2.23 mu m), and C (3.81 mu m) broad-band images as well as Br gamma (n = 7 --> 4, 2.166 mu m) and Br alpha (n = 5 --> 4, 4.052 mu m) hydrogen recombination line images, and 3.29 mu m and 3.4 mu m unidentified feature emission images of the Monoceros R 2 star formation region at a plate scale of similar to 0''.9 pixel(-1) The Brackett line images are combined with 5 GHz data to map the line -of-sight dust extinction to the compact H II region on a small spatia l scale. This extinction map is then used to deredden regions of the H and K images interior to the H II region. IRS 1(SW), the ionizing sou rce, is found to be consistent with a B0 star. Comparison of dereddene d H and K images with the Brackett images and recent high-resolution H CO+ measurements leads to the development of a torus model for the den se molecular gas surrounding the H II region. The 3.29 mu m emission i s found to be coincident with the ring of scattered light at 2.2 mu m and just outside the Br alpha and Br gamma emission. The 3.4 mu m imag e is of too low a signal-to-noise ratio to determine if any variation in the 3.29 to 3.4 mu m emission ratio with distance from the ionizing source is seen; however, 3.4 mu m emission is detected in a ring coin cident with the 3.29 mu m emission.