Sub-arcsecond Radio Observations of the Dwarf Starburst Galaxy NGC 3077

Abstract

We present the first sub-arcsecond radio observations of the nearby dwarf starburst galaxy NGC 3077 obtained with the MERLIN interferometer. We have detected two resolved sources which are coincident with the positions of two discrete X-ray sources detected by Chandra. One of the radio sources is associated with a supernova remnant and the observed radio flux is consistent with having a non-thermal origin. The age of the SNRs of about 760 years is between the average age of the SNRs detected in M82 and those detected in the Milky Way and the Large Magellanic Cloud. We use this detection to calculate a star formation rate (SFR) of 0.28 M_sun year-1 which is similar to the SFR calculated by using far infrared and millimeter observations but larger than the SFR given by optical recombination lines corrected for extinction. The other compact radio source detected by MERLIN which is coincident with the position of an X-ray binary, has the properties of an HII region with a flux density of about 747 microJy which corresponds to an ionizing flux of 6.8x10^50 s-1. A young massive stellar cluster with a mass of about 2x10^5 M_sun, detected by the Hubble Space Telescope could be the responsible for the production of the ionizing flux.