Seeing Red in NGC 1978, NGC 55, and NGC 3109
  Spectra of the intermediate age star cluster NGC 1978 and the dwarf irregular
galaxies NGC 55 and NGC 3109 that span the 0.7 to 1.1um wavelength interval are
discussed. The NGC 1978 spectra are used to examine stochastic effects on the
integrated red light from an intermediate age cluster. The removal of either
the brightest M giant or the brightest C star from the co-added NGC 1978
spectrum has minor effects on the equivalent withs of the Ca triplet. The most
robust signature of C stars in the integrated cluster spectrum at these
wavelengths is the CN band head near 0.79um. The equivalent widths of Ca
triplet lines in the NGC 1978 spectrum and in the spectra of individual cluster
stars are larger than expected for a scaled-solar abundance system, and it is
suggested that these stars have been subject to extra mixing processes. Ca
lines weaken with increasing distance from the disk plane in the NGC 55
spectra. Comparisons with models suggest that the red light from NGC 55 is
dominated by stars with ages 1 - 2 Gyr, in agreement with star-forming
histories (SFHs) obtained from the analysis of CMDs. The NGC 3109 observations
sample three different parts of that galaxy but have a low signal-to-noise
ratio. Comparisons with models suggest that the light from the NGC 3109 disk at
red wavelengths is dominated by RSGs with ages of at most a few tens of Myr, in
qualitative agreement with SFHs that are based on photometric measurements.
