The study of cluster white dwarfs (WDs)
has been invigorated recently bythe Hubble Space
Telescope (HST). Recent WD studies have been
motivated by the new and independent cluster
distance (Renzini et al. 1996), age (von Hippel et
al. 1995; Richer et al. 1997), and stellar
evolution (Koester & Reimers 1996) information
that cluster WDs can provide. An important
byproduct of these studies has been an estimate of
the WD mass contribution in open and globular
clusters. The cluster WD mass fraction is of
importance for understanding the dynamical state
and history of star clusters. It also bears an
important connection to the WD mass fractions of
the Galactic disk and halo. Current evidence
indicates that the open clusters (e.g. von Hippel
et al. 1996; Reid this volume) have essentially
the same luminosity function (LF) as the solar
neighborhood population. The case for the halo is
less clear, despite the number of very good
globular cluster LFs down to nearly 0.1 solar
masses (e.g. Cool et al. 1996; Piotto, this
volume), as the field halo LF is poorly known. For
most clusters dynamical evolution should cause
evaporation of the lowest mass members, biasing
clusters to have flatter present-day mass
functions (PDMFs) than the disk and halo field
populations. Dynamical evolution should also allow
cluster WDs to escape, though not in the same
numbers as the much lower mass main sequence
stars. The detailed connection between cluster
PDMFs and the field IMF awaits elucidation from
observations and the new combined N-body and
stellar evolution models (Tout, this volume).
Nevertheless, the WD mass fraction of clusters
already provides an estimate for the WD mass
fraction of the disk and halo field populations. A
literature search to collect cluster WDs and a
simple interpretive model follow. This is a work
in progress and the full details of the literature
search and the model will be published
elsewhere.
The Future Is Now: The Formation of Single Low‐Mass White Dwarfs in the Solar Neighborhood