van der Kruit to Spitzer: A New Look at the FIR-Radio CorrelationReport as inadecuate



 van der Kruit to Spitzer: A New Look at the FIR-Radio Correlation


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We present an initial look at the far infrared-radio correlation within the star-forming disks of four nearby, nearly face-on galaxies NGC~2403, NGC~3031, NGC~5194, and NGC~6946. Using {\it Spitzer} MIPS imaging and WSRT radio continuum data, we are able to probe variations in the logarithmic 70~$\mu$m-22~cm $q {70}$ flux density ratios across each disk at sub-kpc scales. We find general trends of decreasing $q {70}$ with declining surface brightness and with increasing radius. We also find that the dispersion in $q {70}$ within galaxies is comparable to what is measured {\it globally} among galaxies at around 0.2 dex. We have also performed preliminary phenomenological modeling of cosmic ray electron CR$e^{-}$ diffusion using an image-smearing technique, and find that smoothing the infrared maps improves their correlation with the radio maps. The best fit smoothing kernels for the two less active star-forming galaxies NGC~2403 and NGC~3031 have much larger scale-lengths than that of the more active star-forming galaxies NGC~5194 and NGC~6946. This difference may be due to the relative deficit of recent CR$e^{-}$ injection into the interstellar medium ISM for the galaxies having largely quiescent disks.



Author: Eric J. Murphy; Robert Braun; George Helou; Lee Armus; Jeff D. P. Kenney; the SINGS team

Source: https://archive.org/







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