Identifying Multiple Populations in M71 Using CN
  We have observed the CN features at $\sim$3800 ~\AA~ and 4120~ \AA~ as well
as the CH band at $\sim$4300~\AA~ for 145 evolved stars in the Galactic
globular cluster M71 using the multi-object spectrograph, Hydra, on the
WIYN-3.5m telescope. We use these measurements to create two $\delta$CN indices
finding that both distributions are best fit by two populations, a CN-enhanced
and CN-normal. We find that 42 $\pm$ 4\% of the RGB stars in our sample are
CN-enhanced. The percentage of CN-enhanced is 40 $\pm$ 13\% for the AGB and 33
$\pm$ 9\% for the HB stars, which suggests there are no missing second
generation stars at these stages of stellar evolution. The two generations also
separate in magnitude and color on the HB, which allows us to find the
difference in He abundance between the two populations by fitting appropriate
ZAHBs. The broad range of distances from the cluster's center covered by our
sample allows us to study the dependence of the ratio of the number of first to
second population stars on the distance from the cluster's center, and we find
that this ratio does not vary radially and that the two populations are
spatially mixed. Finally, we compare our identification of multiple populations
with the classification based on the Na-O anti-correlation and the HST UV
photometry, and we find good agreement with both methods.
