The Stellar Archeology of the M33 Disk: Recent Star-Forming History and
  Constraints on the Timing of an Interaction with M31
  Images recorded with MegaCam are used to investigate the recent star-forming
history (SFH) of the Local Group Sc galaxy M33. The properties of the stellar
disk change near R = 8 kpc. Within this radius the star formation rate (SFR)
has been constant with time during at least the past 250 Myr, while at larger
radii the SFR has declined during this same time period. That the recent SFR in
the inner disk has been constant suggests that M33 has evolved in isolation for
at least the past ~ 0.5 Gyr, thereby providing a constraint on the timing of
any recent interaction with M31. The fractional contribution that young stars
make to the total mass of the stellar disk changes with radius, peaking near 8
kpc. Evidence is also presented that the SFR during the past 100 Myr in the
southern half of the galaxy has been ~ 0.4 dex higher than in the northern
half. Finally, structures with sizes spanning many kpc that contain blue
objects - presumably main sequence stars that formed during intermediate epochs
- are identified near the disk boundary. It is argued that these are tidal
features that were pulled from the main body of M33 and - in some cases - are
the fossil remnants of star formation that occured in an extended disk during
intermediate epochs.
