Compact radio sources in M17

Abstract

The classic H II region M17 is one of the best studied across the electromagnetic spectrum. We present sensitive, high angular resolution observations made with the Jansky Very Large Array at 4.96 and 8.46GHz that reveal the presence of 38 compact radio sources, in addition to the well-known hypercompact cometary H II region M17 UC1. For this last source, we find that its spectral index of the order of ∼ 1 is due to a gradient in opacity across its face. Of the 38 compact radio sources detected, 19 have stellar counterparts detected in the infrared, optical, or X-rays. Finally, we discuss the nature of the radio emission from the massive binary system CEN 1a and CEN 1b, concluding that both are most probably non-thermal emitters, although the first is strongly time variable and the second is steady. © 2012. The American Astronomical Society. All rights reserved.