330-MHz radio continuum imaging of the W51 complex

Abstract

We present a 1.1-arcmin-resolution image of the W51 complex made with the Very Large Array at a frequency of 330 MHz. W51A and W51B are resolved into multiple components at metre wavelengths for the first time: most of the compact components have spectra that are self-absorbed at this low observing frequency and these components appear surrounded by thermal plasmas with low emission measures. We estimate the electron temperature towards the brightest subcomponent of W51A (G49.5-0.4e) to be