An Initial Look at the FIR-Radio Correlation within M51a using Spitzer
  We present an initial look at the FIR-radio correlation within the star-forming disk of M51a using {\it Spitzer} MIPS imaging, observed as part of the {\it Spitzer} Infrared Nearby Galaxies Survey (SINGS), and WSRT radio continuum data. At an estimated distance of 8.2 Mpc, we are able to probe the variations in the 70$\micron$/22cm ratios across the disk of M51a at a linearly projected scale of 0.75 kpc. We measure a dispersion of 0.191 dex, comparable to the measured dispersion of the global FIR-radio correlation. Such little scatter in the IR/radio ratios across the disk suggests that we have yet to probe physical scales small enough to observe a breakdown in the correlation. We also find that the global 70$\micron$/22cm ratio of M51a is 25% larger than the median value of the disk, suggesting that the brighter disk regions drive the globally measured ratio. 
Eric J. Murphy (Yale), Lee Armus (SSC/Caltech), George Helou   (SSC/Caltech), Robert Braun (ASTRON, Netherlands), and the SI...