Deep Radio Continuum Imaging of the Dwarf Irregular Galaxy IC10: Tracing Star Formation and Magnetic Fields

TL;DR

This study uses advanced radio observations to analyze star formation and magnetic fields in the dwarf galaxy IC10, revealing a strong correlation between radio and Halpha emissions, significant magnetic field structures, and cosmic-ray electron behavior.

Contribution

It provides the first detailed polarization and radio continuum analysis of IC10 at 6 cm, highlighting the relationship between thermal and non-thermal emissions and magnetic field structures in a dwarf galaxy.

Findings

Radio and Halpha emissions are closely correlated.

Thermal emission accounts for 50% of total radio emission.

Detected polarized emission associated with a non-thermal superbubble.

Abstract

We exploit the vastly increased sensitivity of the Expanded Very Large Array (EVLA) to study the radio continuum and polarization properties of the post-starburst, dwarf irregular galaxy IC10 at 6 cm, at a linear resolution of ~50 pc. We find close agreement between radio continuum and Halpha emission, from the brightest HII regions to the weaker emission in the disk. A quantitative analysis shows a strictly linear correlation, where the thermal component contributes 50% to the total radio emission, the remainder being due to a non-thermal component with a surprisingly steep radio spectral index of between -0.7 and -1.0 suggesting substantial radiation losses of the cosmic-ray electrons. We confirm and clearly resolve polarized emission at the 10-20% level associated with a non-thermal superbubble, where the ordered magnetic field is possibly enhanced due to the compression of the expanding bubble. A fraction of the cosmic-ray electrons has likely escaped because the measured radio emission is a factor of 3 lower than what is suggested by the Halpha inferred SFR.