(Abridged) We present a detailed study of the stellar populations of a
volume-limited sample of early-type galaxies from SDSS, across a range of
environments -- defined as the mass of the host dark matter halo. The stellar
populations are explored through the SDSS spectra, via projection onto a set of
two spectral vectors determined from Principal Component Analysis. We find the
velocity dispersion of the galaxy to be the main driver behind the different
star formation histories of early-type galaxies. However, environmental effects
are seen to play a role (although minor). Galaxies populating the lowest mass
halos have stellar populations on average ~1Gyr younger than the rest of the
sample. The fraction of galaxies with small amounts of recent star formation is
also seen to be truncated when occupying halos more massive than 3E13Msun. The
sample is split into satellite and central galaxies for a further analysis of
environment. Satellites are younger than central galaxies of the same stellar
mass. The younger satellite galaxies in 6E12Msun halos have stellar populations
consistent with the central galaxies found in the lowest mass halos of our
sample (i.e. 1E12Msun). This result is indicative of galaxies in lower mass
halos being accreted into larger halos.Comment: 11 pages, 10 figures. Accepted for publication in MNRA
