Using new UV magnitudes for a sample of early-type galaxies, ETGs, with
published stellar mass-to-light ratios, Upsilon_*, we find a correlation
between UV color and Upsilon_* that is tighter than those previously identified
between Upsilon_* and either the central stellar velocity dispersion,
metallicity, or alpha enhancement. The sense of the correlation is that
galaxies with larger Upsilon_* are bluer in the UV. We conjecture that
differences in the lower mass end of the stellar initial mass function, IMF,
are related to the nature of the extreme horizontal branch populations that are
generally responsible for the UV flux in ETGs. If so, then UV color can be used
to identify ETGs with particular IMF properties and to estimate Upsilon_*.Comment: Submitted for publication in ApJ Letter
