The Relationship Between Molecular Gas and Star Formation in Low-Mass
  E/S0 Galaxies
  We consider the relationship between molecular-gas and star-formation surface
densities in 19 morphologically defined E/S0s with stellar mass <~ 4x10^10
M_sun, paying particular attention to those found on the blue sequence in color
vs. stellar mass parameter space, where spiral galaxies typically reside. While
some blue-sequence E/S0s must be young major-merger remnants, many low-mass
blue-sequence E/S0s appear much less disturbed, and may be experiencing the
milder starbursts associated with inner-disk building as spirals (re)grow. For
a sample of eight E/S0s (four blue-, two mid-, and two red-sequence) whose
CARMA CO(1-0), Spitzer MIPS 24um, and GALEX FUV emission distributions are
spatially resolved on a 750pc scale, we find roughly linear relationships
between molecular-gas and star-formation surface densities within all galaxies,
with power law indices N = 0.6-1.9 (median 1.2). Adding 11 more blue-sequence
E/S0s whose CO(1-0) emission is not as well resolved, we find that most of our
E/S0s have global 1-8 kpc aperture-averaged molecular-gas surface densities
overlapping the range spanned by the disks and centers of spiral galaxies.
While many of our E/S0s fall on the same Schmidt-Kennicutt relation as local
spirals, ~80% (predominantly on the blue sequence) are offset towards
apparently higher molecular-gas star formation efficiency (i.e., shorter
molecular gas depletion time). Possible interpretations of the elevated
efficiencies include bursty star formation similar to that in local dwarf
galaxies, H2 depletion in advanced starbursts, or simply a failure of the
CO(1-0) emission to trace all of the molecular gas.
