Mapping Star Formation Rates in the Nearby Universe

A key component of many extragalactic studies is the correlation of a galaxy's overall star formation rate with the incidence or frequency of a particular type of astronomical object, like supernovae, luminous X-ray binaries, or ultraluminous X-ray sources. These correlations have allowed for considerable progress in understanding the nature, formation, and diversity of these objects. However, star formation is not uniform across a galaxy, and a galaxy's overall star formation rate may be dominated by a handful of intense knots of star formation or may be made up rather uniformly over the entire disk. Given this, we have been making maps of local star formation rates to better assess the correlations of star formation rate with certain types of objects, and we present our latest results. We make our star formation rate maps using far ultraviolet (FUV) data from the Galaxy Evolution Explorer Telescope (GALEX) and 24-micron infrared data from the Spitzer Space Telescope. Corrections are made to the FUV and IR images to account for background and correct for differences in angular resolution. Maps of star formation rate per unit area are then generated by a weighted combination of the FUV and IR images in the appropriate units. We then convert these to maps of star formation rate taking into account the distance to the galaxy, which is often poorly known. We also generate companion images of the uncertainty in star formation rate, both statistical and due to uncertainties in distance.