Physics & Astronomy Colloquium
3:30 PM, Friday, November 12, 2010
Room 155, Chem-Phys Building
Dr. Louis-Gregory Strolger
Department of Physics and Astronomy
Western Kentucky University
Constraints on the Type Ia Supernova Progenitors from Hubble Space Telescope Treasury Surveys
I will present the state of the current observational constraints on SN Ia progenitors,
based on volumetric rate measures (to z = 2) and host galaxy demographics.
At present, SNe Ia in high and low redshift galaxies show inconsistent results
on the implied progenitors responsible for these important cosmological tools.
At its heart, the debate now hinges on two important factors: (1) the metallicity of the
progenitor and its impact on event luminosity and production
efficiency; and (2) the time required for a SN~Ia progenitor system to
develop to an explosion from an episode of star-formation (commonly called the ``delay time'').
While these are conceptually measurable factors in low redshift (z< 0.1) galaxies,
attempts to do so have been muddled by two degenerate effects: (1) population age, which
steadily increases the range of metallicity within a given environment,
and (2) rate of active star formation, which mix-up the incubation time
between SN events and progenitor formation. Results
from high redshift (z> 1) surveys, which by the nature of being age-limited
surveys should elucidate the nature of SNe Ia, have instead
implied very long (3 to 4 Gyr) delay times that are largely
inconsistent with the relatively short (< 1 Gyr) times predicted from
binary star evolutionary models and low-z observations.
Refreshments will be served in CP 179 at 3:15 PM