Infrared line observations of DR 21, W75N, and K3-50

Abstract

We present hydrogen Brackett ..cap alpha.. line observations of obscured and very compact radio components in the regions of DR 21, W75N, and K3-50, and of the (Ne II) 12.8 ..mu..m line of DR 21. We derive the extinction to these components. In DR 21, the extinction varies markedly from A/sub v/approx.18 mag to the infrared source DR 21(S) to 120 mag and greater to radio components A, B, and C which we suggest form an ionization blister at the far side of the DR 21 molecular cloud. Through the core of DR 21, the ratio of A/sub v/ to /sup 13/CO column density is approx.1 x 10/sup -15/ mag cm/sup 2/ which is larger than the corresponding ratio in cooler, less dense clouds. The extinction is A/sub v/=4(+6; -4) to the H II region W75N. In the K3-50 region, the extinction varies from A/sub v/=4 +- 2 mag to radio component A to approx.100 mag to radio component Cl.