Star formation histories within the Antennae galaxies (Arp 244)

With the imagery from Galaxy Evolution Explorer, Hubble Space Telescope, Two Micron All Sky Survey and Spitzer and at the resolution of Multiband Imaging Photometer for Spitzer (MIPS) 24 mu m (similar to 6 arcsec), we study the variations of the broad-band spectral energy distributions of star-forming regions within the nearest prototypal major merger - the Antennae galaxies. By including MIPS 24 mu m dust emission into stellar population analysis, we reliably, albeit roughly, constrain the star formation histories of these 24 mu m selected star-forming regions across the merging discs 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 discs following their second close encounter. Furthermore, we suggest that the star formation in the southern and (especially) north-western 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 mu m, whose total 4.5 mu m emission (>= 80 per cent from both hot dust and atomic/molecular lines) is comparable with that of the two galactic nuclei.