Anomalous Stellar Populations in LSB Galaxies
  We present new HST WFC3 near-IR observations of the CMD's in two LSB
galaxies, F575-3 and F615-1, notable for having no current star formation based
on a lack of H$\alpha$ emission. Key features of the near-IR CMD's are
resolved, such as the red giant branch (RGB), the asymptotic giant branch (AGB)
region and the top of the blue main sequence (bMS). F575-3 has the bluest RGB
of any CMD in the literature, indicating an extremely low mean metallicity.
F615-1 has unusually wide RGB and AGB sequences suggesting multiple episodes of
star formation from metal-poor gas, possibly infalling material. Both galaxies
have an unusual population of stars to the red of the RGB and lower in
luminosity than typical AGB stars. These stars have normal optical colors but
abnormal near-IR colors. We suggest that this population of stars might be
analogous to local peculiar stars like Be stars with strong near-IR excesses
owing to a surrounding disk of hot gas.
