Deep CCD photometry of the two richest star clusters in the CFHT Open Star Cluster Survey has allowed us to statistically catalogue over 100 white dwarfs. Further multi-object spectroscopic observations of these candidates will confirm their spectral type (DA/DB/peculiar nature), as well as provide constraints on the masses of the objects. For the case of the intermediate aged cluster NGC 2099 (M37), our photometry is faint enough to accurately detect the remnants of the most massive progenitor cluster stars under the Type I Sne limit. Therefore, the CMD of the cluster exhibits a well defined white dwarf `clump' caused by the decreased rate of cooling of these stars as they age. By accounting for incompleteness corrections and statistically removing field objects and faint background galaxies, we establish a white dwarf luminosity function for the cluster, the peak of which is interpreted to represent it's white dwarf cooling age (MV = 11.95 +/- 0.30). Folding in the main-sequence lifetime of the progenitor stars provides the age of the cluster (566 +/- 165 Myrs). We compare this age to the main-sequence turn-off age by investigating the fit of the observed rich main-sequence to a variety of up-to-date theoretical isochrones. The results indicate an excellent agreement between the two ages for solar metallicity models with an age of 520 Myrs (adopting convective core-overshooting). Furthermore, after carefully accounting for uncertainties in the ages, we can rule out a non core-overshooting model of age 300-350 Myrs for the cluster.
American Astronomical Society Meeting Abstracts
- Pub Date:
- December 2001