Using observed GALEX far-ultraviolet (FUV) fluxes and VLA images of the 21-cm HIcolumn densities, along with estimates of the local dust abundances, we measure the volume densities of a sample of actively star-forming giant molecular clouds (GMCs) in the nearby spiral galaxy M83 on a typical resolution scale of 170 pc. Our approach is based on an equilibrium model for the cycle of molecular hydrogen formation on dust grains and photodissociation under the influence of the FUV radiation on the cloud surfaces of GMCs. We find a range of total volume densities on the surface of GMCs in M83, namely 0.1-400cm^-3^ inside R_25_, 0.5-50cm^-3^ outside R_25_. Our data include a number of GMCs in the HI-ring surrounding this galaxy. Finally, we discuss the effects of observational selection, which may bias our results.

Cone search capability for table J/A+A/489/533/table1 (Locations and FUV fluxes of candidate photodissociation regions (PDRs))