The Radio-FIR correlation in the Milky Way

TL;DR

This study examines the scale and location dependence of the radio-FIR correlation in the Milky Way, revealing a tight correlation at 20-50 pc scales and a modest latitude dependence linked to star formation activity.

Contribution

It provides the first detailed analysis of the spatial scale and galactic location effects on the radio-FIR correlation within our galaxy.

Findings

Correlation exists down to ~4 pc scales.

Correlation tightens at 20-50 pc scales.

q_mean varies modestly with galactic latitude.

Abstract

We investigate the scale on which the correlation arises between the 843 MHz radio and the 60 micron 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 consistent 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 nearby galaxies that show elevated values for q in regions of enhanced star formation.