Tracing molecular hydrogen with atomic hydrogen in m81 and other nearby galaxies

Abstract

We present our progress on a detailed study of M81 in the radio, ultraviolet and infrared wavelengths, in which we attempt to use Hi produced in photodisso-ciation regions (PDRs) as a tracer for molecular hydrogen. Radio (VLA), UV (Galex) and IR (Spitzer) data are all available at about 6 arcsec resolution or better, corresponding to a linear scale of little over 100 parsec. We expect to pursue the viability of the use of Hi as a tracer for H2 across a variety of nearby galaxies, including NGC2403, M33 and M83, using VLA and GALEX data as a major extension to the existing studies of e.g. M101 and M81 in this context.