Spectral Energy Distribution of z>1 Type Ia Supernova Hosts in GOODS:
  Constraints on Evolutionary Delay and the Initial Mass Function
  We identify a sample of 22 host galaxies of Type Ia Supernovae (SNe Ia) at
redshifts 0.95<z<1.8 discovered in the Hubble Space Telescope (HST)
observations of the Great Observatories Origins Deep Survey (GOODS) fields. We
measure the photometry of the hosts in Spitzer Space Telescope and ground-based
imaging of the GOODS fields to provide flux densities from the U-band to 24
microns. We fit the broad-band photometry of each host with Simple Stellar
Population (SSP) models to estimate the age of the stellar population giving
rise to the SN Ia explosions. We break the well-known age-extinction degeneracy
in such analyses using the Spitzer 24 micron data to place upper limits on the
thermally reprocessed, far-infrared emission from dust. The ages of these
stellar populations give us an estimate of the delay times between the first
epoch of star-formation in the galaxies and the explosion of the SNe Ia. We
find a bi-modal distribution of delay times ranging from 0.06 - 4.75 Gyrs. We
also constrain the first-epoch of low mass star formation using these results,
showing that stars of mass <8 Msun were formed within 3 Gyrs after the Big Bang
and possibly by z~6. This argues against a truncated stellar initial mass
function in high redshift galaxies.
