The Radio-FIR Correlation in the Milky Way

Abstract We investigate the scale on which the correlation arises between the 843 MHz radio and the 60 μm far-infrared (FIR) emission from star forming regions in the Milky way. The correlation, which exists on the smallest scales investigated (down to ≈ 4 pc), becomes noticeably tight on fields of size 30′, corresponding to physical scales of ≈ 20–50 pc. The FIR to radio flux ratio on this scale is consi stent with the radio emission being dominated by thermal emission. We also investigate the location dependence of q mean , a parameter measuring the mean FIR to radio flux ratio, of a sample of star forming regions. We show that q mean displays a modest dependence on galactic latitude. If this is interpreted as a dependence on the intensity of star formation activity, the result is consistent with studies of the Large Magellanic Cloud (LMC) and other near by galaxies that show elevated values for q in regions of enhanced star formation.