  Deep images obtained with MegaCam and WIRCam on the Canada-France-Hawaii
Telescope are used to probe the stellar content outside of the central
star-forming regions of M82. Stars evolving on the asymptotic giant branch
(AGB) are traced along the major axis out to projected distances of 12 kpc,
which corresponds to 13 disk scale lengths. The specific frequency (SF) of
bright AGB stars in the outer disks of M82 and the Sc galaxy NGC 2403 are
identical, suggesting that the specific star formation rates (SFR) in these
galaxies during intermediate epochs were similar. This similarity in stellar
content, coupled with the presence of an extended stellar disk, is consistent
with M82 having been a late-type disk galaxy prior to interacting with M81.
Still, there is a paucity of red supergiants (RSGs) in the outer disk of M82
when compared with NGC 2403, indicating that the SFR in the outer regions of
M82 during the past ~ 0.1 Gyr has declined dramatically with respect to that in
isolated late-type galaxies. A mixture of bright main sequence stars, RSGs, and
AGB stars are detected out to minor axis distances of 7 kpc along the outflow.
It is suggested that the young and intermediate aged stars in the extraplanar
regions formed in structures similar to M82 South, and that these were
subsequently disrupted by the tidal action of M82.

Astrophysics