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The First Stars and Galaxies: Challenges for the Next Decade Participants
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Talk
Title: The Cosmic Star Formation Rate Density since z ~ 10: Constraints on Galaxies in the First Gyr Author(s): Garth Illingworth Abstract: The recent extraordinarily deep WFC3/IR data from the HST HUDF09 program has dramatically expanded our insights into the galaxy population at z ~ 7-8-9, and given us hints as to the population at z ~ 10. In particular, as part of our program of identifying and characterizing the galaxy population at high redshift (z > 6) we have been undertaking a thorough analysis of the luminosity functions to much lower luminosities than previous studies. We have used very deep fields (the HUDF, HUDF09 and the HUDF05 datasets), as well as extremely faint objects from highly magnified sources from cluster lensing surveys to derive the contribution from lower luminosity galaxies to as faint as 0.03-0.06 L* from redshift 2-7. We have incorporated recent results on the contribution of ULIRGS and sub-mm star-forming galaxies to indicate that in the first 1-2 Gyr the dominant contributors to the star formation rate density in the universe are the lower luminosity, and likely lower mass objects, that are fully represented in the Lyman Break population at z ~ 4-7 and at earlier times. Evidence from the HST WFC3/IR and Spitzer IRAC data over the HUDF suggests that these z ~ 7-8 galaxies include earlier populations that reach back to z > 10. I will contrast the striking evolution from z ~ 7-8-9 to z ~ 6 and later, including the stellar population characteristics and the results from recent structural analyses. I will discuss how this period from 0.5 billion years to 1-2 billion years encompasses fascinating evolutionary changes in the broad nature of the galaxy population based on the new HUDF09 WFC3/IR data.
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