A New, Deep JVLA Radio Survey of M33

Abstract

We have performed new 1.4 and 5 GHz observations of the Local Group galaxy M33 with the Jansky Very Large Array. Our survey has a limiting sensitivity of 20  μ Jy (4 σ ) and a resolution of 5.″9 (FWHM), corresponding to a spatial resolution of 24 pc at 817 kpc. Using a new multiresolution algorithm, we have created a catalog of 2875 sources, including 675 with well-determined spectral indices. We detect sources at the position of 319 of the X-ray sources in the Tüllmann et al. Chandra survey of M33, the majority of which are likely to be background galaxies. The radio source coincident with M33 X-8, the nuclear source, appears to be extended. Along with numerous H ii regions or portions of H ii region complexes, we detect 155 of the 217 optical supernova remnants (SNRs) included in the lists of Long et al. and Lee & Lee, making this by far the largest sample of remnants at known distances with multiwavelength coverage. The remnants show a large dispersion in the ratio of radio to X-ray luminosity at a given diameter, a result that challenges the current generation of models for synchrotron radiation evolution in SNRs.