Nature and Nurture at the Peak of Cosmic Star Formation: A Census of Galaxy Environments at z=2

Tal Tomer, New Haven CT

Investigators

Abstract

Dr. Tomer Tal is awarded an NSF Astronomy and Astrophysics Postdoctoral Fellowship to carry out a program of research and education at the University of California, Santa Cruz. Precisely how galaxies initially form and how they change throughout their lifetimes are among the least understood problems in astrophysics. The properties of nearby galaxies depend strongly on their host environment with observed correlations among color, morphology, and local density. It remains unknown whether the physical characteristics of galaxies were determined at the time of their formation or are the result of ongoing evolution through environmentally induced processes. In this project the fellow will perform a statistical analysis of galaxy environments at the peak of cosmic star formation, when a large fraction of local galaxies were formed and assembled. He will apply a unique method that he demonstrated at intermediate galaxy distances and will extract luminosity functions for a large sample of galaxy groups and clusters at a redshift of z = 2, revealing the typical environments of the high redshift Universe. He will then employ these results to test whether the local correlations between galaxy properties and environment were already in place 10 billion years ago. To do so, the fellow will utilize the data sets of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) and the 3D-HST survey, complementary surveys of the early Universe with the new infrared camera on the Hubble Space Telescope. This is the first time that such a study will be possible at redshift of z ~ 2, and it will unveil clues regarding the balance between internal and external processes at great distances. The broader impacts of this project include a significant educational component. First, the fellow will develop and teach a high-school level extragalactic astronomy class as part of COSMOS, the California State Summer School for Mathematics and Science. Second, he will volunteer at the public observing nights hosted by the Santa Cruz Astronomy Club at the Harvey West Park Scout House. Both of these activities promote scientific literacy through direct involvement and contact with the public.