The Masses of Supernova Remnant Progenitors in M83
  We determine the ages of the young, resolved stellar populations at the
locations of 237 optically-identified supernova remnants in M83. These age
distributions put constraints on the progenitor masses of the supernovae that
produced 199 of the remnants. The other 38 show no evidence for having a young
progenitor and are therefore good Type Ia SNR candidates. Starting from Hubble
Space Telescope broadband imaging, we measured resolved stellar photometry of
seven archival WFC3/UVIS fields in F336W, F438W, and F814W. We generate
color-magnitude diagrams of the stars within 50 pc of each SNR and fit them
with stellar evolution models to obtain the population ages. From these ages we
infer the progenitor mass that corresponds to the lifetime of the most
prominent age that is $<$50 Myr. In this sample, there are 47 SNRs with
best-fit progenitor masses $>$15 M$_{\odot}$, and 5 of these are $>$15
M$_{\odot}$ at 84% confidence. This is the largest collection of high-mass
progenitors to date, including our highest-mass progenitor inference found so
far, with a constraint of $<$8 Myr. Overall, the distribution of progenitor
masses has a power-law index of $-3.0^{+0.2}_{-0.7}$, steeper than Salpeter
initial mass function ($-2.35$). It remains unclear whether the reason for the
low number of high-mass progenitors is due to the difficulty of finding and
measuring such objects or because only a fraction of very massive stars produce
supernovae.
