  We present new observations of very faint white dwarfs (WDs) in the rich open
star cluster NGC 2099 (M37). Following deep, wide field imaging of the cluster
using CFHT, we have now obtained spectroscopic observations of candidate WDs
using both GMOS on Gemini and LRIS on Keck. Of our 24 WD candidates (all
fainter than V = 22.4), 21 are spectroscopically confirmed to be bona fide WDs,
4-5 of which are most likely field objects. Fitting 18 of the 21 WD spectra
with model atmospheres, we find that most WDs in this cluster are quite massive
(0.7-0.9 Msun), as expected given the cluster's young age (650 Myr) and, hence,
high turnoff mass (~2.4 Msun). We determine a new initial-final mass
relationship and almost double the number of existing data points from previous
studies. The results indicate that stars with initial masses between 2.8 and
3.4 Msun lose 70-75% of their mass through stellar evolution. For the first
time, we find some evidence of a metallicity dependence on the initial-final
mass relationship.
