  The star formation history of nearby early-type galaxies is investigated via
numerical modelling. Idealized hydrodynamical N-body simulations with a star
formation prescription are used to study the minor merger process between a
giant galaxy (host) and a less massive spiral galaxy (satellite) with
reasonable assumptions for the ages and metallicities of the merger
progenitors. We find that the evolution of the star formation rate is extended
over several dynamical times and shows peaks which correspond to pericentre
passages of the satellite. The newly formed stars are mainly located in the
central part of the satellite remnant while the older stars of the initial disk
are deposited at larger radii in shell-like structures. After the final plunge
of the satellite, star formation in the central part of the remnant can
continue for several Gyrs depending on the star formation efficiency. Although
the mass fraction in new stars is small, we find that the half-mass radius
differs from the half-light radius in the V and H bands. Moreover synthetic 2D
images in J, H, NUV, Hb and V bands, using the characteristic filters of the
Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST), reveal that
residual star formation induced by gas-rich minor mergers can be clearly
observed during and after the final plunge, especially in the NUV band, for
interacting systems at (z<0.023) over moderate numbers of orbits (~2 orbits
correspond to typical exposure times of ~3600 sec). This suggests that WFC3 has
the potential to resolve these substructures, characterize plausible past
merger episodes, and give clues to the formation of early-type galaxies.
