Star formation and molecular gas in M83

We compare star formation rates and efficiencies, obtained from different star formation tracers, before and after compensation for internal extinction due to gas and dust, in the barred spiral galaxy M83 (NGC 5236). We use far-UV continuum, B-band continuum, and Ha line images to estimate the star formation rate in the disk of this galaxy at 25" resolution. We use the total gas map, derived from CO (J = 1 -> 0) and H I data, to compensate for internal extinction. We find that the star formation rate estimates based on the different data agree well when corrections for internal extinction have been made. The star formation rate is particularly high in the nuclear region, at the bar ends, and in the spiral arms. Combined with the total gas mass map, the star formation rates provide estimates of the star formation efficiencies in the disk at 25" resolution. The star formation efficiency map is more patchy than the star formation rate map. There is evidence of an increased star formation efficiency along the spiral arms, i.e., not only do the arms present regions of higher gas mass surface density, the efficiency for making stars is also increased in them.