Large-scale distributions of mid- and far-infrared emission from the center to the halo of M82 revealed with AKARI

TL;DR

This study uses AKARI infrared observations to map dust and PAH distributions in M82, revealing their presence in the halo and their association with ionized and neutral gas components, shedding light on galaxy feedback processes.

Contribution

First detailed mid- and far-infrared imaging of M82's halo showing dust and PAHs far from the disk, highlighting their expulsion by starbursts and interactions.

Findings

Detection of faint halo emission indicating dust and PAHs in the galaxy's outskirts.

Strong correlation between PAH and Hα emission suggests PAHs are mixed with ionized superwind gas.

Evidence that dust and PAHs are expelled into the halo through starburst activity and galaxy interactions.

Abstract

The edge-on starburst galaxy M82 exhibits complicated distributions of gaseous materials in its halo, which include ionized superwinds driven by nuclear starbursts, neutral materials entrained by the superwinds, and large-scale neutral streamers probably caused by a past tidal interaction with M81. We investigate detailed distributions of dust grains and polycyclic aromatic hydrocarbons (PAHs) around M82 to understand their interplay with the gaseous components. We performed mid- (MIR) and far-infrared (FIR) observations of M82 with the Infrared Camera and Far-Infrared Surveyor on board AKARI. We obtain new MIR and FIR images of M82, which reveal both faint extended emission in the halo and very bright emission in the center with signal dynamic ranges as large as five and three orders of magnitude for the MIR and FIR, respectively. We detect MIR and FIR emission in the regions far away from the disk of the galaxy, reflecting the presence of dust and PAHs in the halo of M82. We find that the dust and PAHs are contained in both ionized and neutral gas components, implying that they have been expelled into the halo of M82 by both starbursts and galaxy interaction. In particular, we obtain a tight correlation between the PAH and H$\alpha$ emission, which provides evidence that the PAHs are well mixed in the ionized superwind gas and outflowing from the disk.