An analysis of the FIR/RADIO Continuum Correlation in the Small Magellanic Cloud

TL;DR

This study examines the FIR/radio continuum correlation in the Small Magellanic Cloud across various scales, revealing a strong correlation down to 15 pc and insights into the roles of thermal emission and cosmic rays.

Contribution

It provides the first detailed analysis of FIR/RC correlation at small scales in the SMC, highlighting the influence of thermal fractions and cosmic ray diffusion.

Findings

Good FIR/RC correlation down to ~15 pc

RC emission increases faster than FIR in active regions

Thermal fraction explains the FIR/RC correlation

Abstract

The local correlation between far-infrared (FIR) emission and radio-continuum (RC) emission for the Small Magellanic Cloud (SMC) is investigated over scales from 3 kpc to 0.01 kpc. Here, we report good FIR/RC correlation down to ~15 pc. The reciprocal slope of the FIR/RC emission correlation (RC/FIR) in the SMC is shown to be greatest in the most active star forming regions with a power law slope of ~1.14 indicating that the RC emission increases faster than the FIR emission. The slope of the other regions and the SMC are much flatter and in the range of 0.63-0.85. The slopes tend to follow the thermal fractions of the regions which range from 0.5 to 0.95. The thermal fraction of the RC emission alone can provide the expected FIR/RC correlation. The results are consistent with a common source for ultraviolet (UV) photons heating dust and Cosmic Ray electrons (CRe-s) diffusing away from the star forming regions. Since the CRe-s appear to escape the SMC so readily, the results here may not provide support for coupling between the local gas density and the magnetic field intensity.