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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.