Large-scale distributions of mid- and far-infrared emission from the center to the halo of M 82 revealed with AKARI

¹ Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan e-mail: kaneda@u.phys.nagoya-u.ac.jp
² Advanced Technology Center, National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588, Japan
³ Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Kanagawa 229-8510, Japan
⁴ Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
⁵ Academia Sinica, Institute of Astronomy and Astrophysics, Taipei 10617, Taiwan

Received: 30 November 2009
Accepted: 11 February 2010

Abstract

Context. The edge-on starburst galaxy M 82 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 M 81.

Aims. We investigate detailed distributions of dust grains and polycyclic aromatic hydrocarbons (PAHs) around M 82 to understand their interplay with the gaseous components.

Methods. We performed mid- (MIR) and far-infrared (FIR) observations of M 82 with the infrared camera (IRC) and far-infrared surveyor (FIS) onboard AKARI.

Results. We obtained new MIR and FIR images of M 82, which reveal both faint extended emission in the halo and very bright emission in the center with signal dynamic ranges as broad as five orders of magnitude for the MIR and three for FIR, respectively. We detected MIR and FIR emission in the regions far away from the disk of the galaxy, reflecting the dust and PAHs in the halo of M 82.

Conclusions. 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 M 82 by both starbursts and galaxy interaction. In particular, we obtain a tight correlation between the PAH and Hα emission, which provides evidence that the PAHs are well mixed in the ionized superwind gas and flowing out from the disk.