Mid-IR FORCAST/SOFIA Observations of M82

TL;DR

This study maps M82 in multiple mid-infrared bands using SOFIA/FORCAST, revealing detailed dust emission morphology, estimating dust properties, and comparing with other infrared data to understand the galaxy's dust components.

Contribution

First detailed mid-IR maps of M82 at multiple wavelengths with high resolution, analyzing dust emission morphology and properties across different dust components.

Findings

Strong emission along the galaxy's inner region

Different emission morphology across wavelengths

Estimated dust temperatures and masses at emission peaks

Abstract

We present 75"x75" size maps of M82 at 6.4 micron, 6.6 micron, 7.7 micron, 31.5 micron, and 37.1 micron with a resolution of ~4" that we have obtained with the mid-IR camera FORCAST on SOFIA. We find strong emission from the inner 60" (~1kpc) along the major axis, with the main peak 5" west-southwest of the nucleus and a secondary peak 4" east-northeast of the nucleus. The detailed morphology of the emission differs among the bands, which is likely due to different dust components dominating the continuum emission at short mid-IR wavelengths and long mid-IR wavelengths. We include Spitzer-IRS and Herschel/PACS 70 micron data to fit spectral energy distribution templates at both emission peaks. The best fitting templates have extinctions of A_V = 18 and A_V = 9 toward the main and secondary emission peak and we estimated a color temperature of 68 K at both peaks from the 31 micron and 37 micron measurement. At the emission peaks the estimated dust masses are on the order of 10^{4} M_sun.