Star Formation Histories within the Antennae Galaxies (Arp 244)
  With the imagery from GALEX, HST, 2MASS, and Spitzer, and at the resolution
of MIPS 24 micron(~6"), we study the variations of the broadband spectral
energy distributions (SEDs) of star-forming regions within the nearest
prototypal major merger -- the Antennae galaxies. By including MIPS 24 micron
dust emission into stellar population analysis, we reliably, albeit roughly,
constrain the star formation histories of these 24 micron selected star-forming
regions across the merging disks of the Antennae. Our population analysis is
consistent with the star formation scenario that, most regions across the whole
system are at a modest level of star formation with the exception of some
localized intense starburst sites in the well-known overlap regions and the
western-loop regions of northern galaxy NGC 4038. Compared with all the other
regions, the young overlap regions currently (<10 Myr) are experiencing much
more violent enhancement of star formation. Across the overlap regions, we
suggest two sequential star formation paths which we interpret as the imprints
of the interpenetrating process of the two merging disks following their second
close encounter. And we suggest that the star formation in the southern and
(especially) northwestern edges of the overlap zone may have been just
triggered by pre-starburst shocks. The well-known mid-infrared "hotspot" in the
overlap regions is also a "hotspot" at 4.5 micron, whose total 4.5 micron
emission (>=80% from both hot dust and atomic/molecular lines) is comparable
with that of the two galactic nuclei.
