||440, UP2010: Have Observations Revealed a Variable Upper End of the Initial Mass Function?
||Lee, J. C.; de Paz, A. G.; Tremonti, C.; Kennicutt, R.; Loval Volume Legacy Team
||A great deal of our understanding of
star formation in the local universe
has been built upon an extensive foundation
of Hα observational studies.
However, recent work in the ultraviolet (UV) with GALEX
has shown that
star formation rates (SFRs) inferred from
Hα in galactic environments
characterized by low stellar and gas densities tend to be less
than those based on
the UV luminosity.
The origin of the discrepancy is actively debated because one
possible explanation is that the stellar initial mass function
is systematically deficient in high mass stars
in such environments. In this contribution,
we summarize our work on this topic using a dwarf galaxy
of ∼300 late-type galaxies in the 11 Mpc Local Volume.
The sample allows us to examine the
discrepancy between Hα and UV SFRs
using a statistical number of galaxies
with activities less than 0.1 M☉ yr-1.
A range of potential causes for such an effect are
reviewed. We find that
while the IMF hypothesis is not inconsistent with our observations,
remain that must be investigated further
before a final conclusion can be drawn.