Compact radio sources in M17

TL;DR

This study uses high-resolution JVLA observations at 4.96 and 8.46 GHz to identify 38 compact radio sources in M17, revealing their properties, counterparts, and emission mechanisms, including the nature of the binary system CEN 1a and 1b.

Contribution

The paper provides the first high-resolution radio survey of M17 at these frequencies, identifying new compact sources and analyzing their spectral and emission characteristics.

Findings

38 compact radio sources detected in M17

19 sources have stellar counterparts in other wavelengths

CEN 1a and 1b are likely non-thermal emitters with different variability behaviors

Abstract

The classic HII 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 (JVLA) at 4.96 and 8.46 GHz that reveal the presence of 38 compact radio sources, in addition to the well known hypercompact cometary HII region M17 UC1. For this last source we find that its spectral index of value $\sim$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 1b, concluding that both are most probably non-thermal emitters, although the first is strongly time variable and the second is steady.