Jason Kalirai
UCO/Lick Observatory
University of California at Santa Cruz
Stellar Remnants as Cosmological Probes
Monday, April 21, 2008, 4:00 p.m.
Location: Thornton Hall 411
Refreshments at 3:45 p.m.
ABSTRACT
White dwarfs represent the eventual end products of 98% of all stars. As
such, their luminosity and mass distributions can be used to understand
the properties of their progenitor populations (e.g., the initial mass
function of stars). In this talk, I will summarize recent results from
two large imaging and spectroscopic surveys aimed at uncovering these
stellar cinders in nearby resolved clusters. With ultra-deep HST/ACS
imaging of globulars, we have now firmly established the ages of the first
structures to form in the Galactic halo and disk. A similar survey of
white dwarfs in rich open clusters (over a large range of age and
metallicity) has uncovered hundreds of these objects that can be
spectroscopically studied. The data have led to unprecedented constraints
on the initial-to-final mass relation (i.e., what mass main-sequence star
maps to white dwarf mass) over a large mass range (M_initial = 1 -- 7
Msun), and therefore are a powerful input to chemical evolution models of
galaxies including enrichment in the interstellar medium. Finally, I will
discuss direct empirical evidence that stellar mass loss is much more
efficient in high metallicity environments. This result is critical in
interpreting the UV upturn in elliptical galaxies, the dearth of planets
around white dwarfs, and the different rates (and properties) of type Ia
SNe in elliptical vs spiral galaxies.