A Herschel-ATLAS study of dusty spheroids: probing the minor-merger
  process in the local Universe
  We use multi-wavelength (0.12 - 500 micron) photometry from Herschel-ATLAS,
WISE, UKIDSS, SDSS and GALEX, to study 23 nearby spheroidal galaxies with
prominent dust lanes (DLSGs). DLSGs are considered to be remnants of recent
minor mergers, making them ideal laboratories for studying both the
interstellar medium (ISM) of spheroids and minor-merger-driven star formation
in the nearby Universe. The DLSGs exhibit star formation rates (SFRs) between
0.01 and 10 MSun yr^-1, with a median of 0.26 MSun yr^-1 (a factor of 3.5
greater than the average SG). The median dust mass, dust-to-stellar mass ratio
and dust temperature in these galaxies are around 10^7.6 MSun yr^-1, ~0.05% and
~19.5 K respectively. The dust masses are at least a factor of 50 greater than
that expected from stellar mass loss and, like the SFRs, show no correlation
with galaxy luminosity, suggesting that both the ISM and the star formation
have external drivers. Adopting literature gas-to-dust ratios and star
formation histories derived from fits to the panchromatic photometry, we
estimate that the median current and initial gas-to-stellar mass ratios in
these systems are ~4% and ~7% respectively. If, as indicated by recent work,
minor mergers that drive star formation in spheroids with (NUV-r)>3.8 (the
colour range of our DLSGs) have stellar mass ratios between 1:6 and 1:10, then
the satellite gas fractions are likely >50%.
