Predoctoral Projects, 2015

Project Title: The Chandra-COSMOS Survey

Project Advisor: Dr. Martin Elvis

Background: Deep surveys of regions of the sky have been responsible for major breakthroughs in understanding the evolution of quasars and galaxies through cosmic time. The Hubble Deep Field is the most famous example. But most surveys cover too narrow an area on the sky to deal with 'cosmic variance'. Because the universe has structure on large scales - up to 50 Mpc, far larger than clusters of galaxies - to get an 'average' piece of the universe in your survey it has to cover at least this scale. The variation you see from field to field in smaller area surveys comes from this and is called 'cosmic variance'.

COSMOS is a survey that is large enough (1.4x1.4 deg, ~40Mpc x 40Mpc at z=1) that cosmic variance is small. COSMOS has been surveyed deeply by virtually all the major telescopes and satellites operating, and more will be added. The result is an unprecendented omni-wavelength survey of a fair sample of the universe.

Scientific Questions: The supermassive black holes in AGNs appear to influence galaxy evolution: their growth through accretion and mergers is synchronized with the growth of galaxies. Where do AGNs live? How does the deep obscuration many AGN suffer relate to the Ultra-luminous IR galaxies - are ULIRGs a precursor to quasars? Do stars form unusually many high mass stars - which more often lead to X-ray binaries - at high redshift? How do mergers influence this stellar population? The number of questions that can be asked of the COSMOS data is limited only by our imagination.

Scientific Methodology: The Chandra-COSMOS survey is a 1.8Msec survey of the inner ~sq.deg of the COSMOS region, where we know that all cosmic densities are represented. The field is deep enough to see both the bulk of the AGNs making up the X-ray background, and to see normal and starburst galaxies, out to substantial redshifts, starting to become prominent. We will use both the sources and a 'stacking' analysis on galaxies to study galaxy and AGN evolution and co-evolution in X-rays and relate it to all other wavelengths, using the rich COSMOS data set.


Clay Fellow Warren Brown