Characterizing the X-ray Properties and Evolution of Distant Galaxies Using Deep Extragalactic Surveys

Open Access
Lehmer, Bret D
Graduate Program:
Astronomy and Astrophysics
Doctor of Philosophy
Document Type:
Date of Defense:
August 01, 2007
Committee Members:
  • W Nielsen Brandt, Committee Chair
  • Donald P Schneider, Committee Member
  • Michael Eracleous, Committee Member
  • Caryl Ann Gronwall, Committee Member
  • Douglas Cowen, Committee Member
  • normal galaxies
  • astronomy
  • X-rays
  • Chandra
With the advent of deep extragalactic X-ray surveys conducted using the Chandra X-ray Observatory (Chandra), it has now become possible to investigate the X-ray properties and evolution of distant populations of "normal" galaxies. Normal galaxies have X-ray emission that originates primarily from X-ray binary populations, supernovae, supernova remnants, hot interstellar gas, and O-stars; these galaxies are not heavily influenced by the presence of luminous active galactic nuclei (AGNs). In this thesis, I study the X-ray properties and evolution of normal galaxy populations over significant fractions of cosmic history, which for some populations extends from the present day to cosmic look-back times that correspond to 85-95% of the age of the Universe (i.e., z ~ 3-6). These studies have been carried out using two of the most well-studied extragalactic multiwavelength survey fields: the 2 Ms Chandra Deep Field-North (CDF-N) and the Extended Chandra Deep Field-South (E-CDF-S), which is composed of the central 1 Ms Chandra Deep Field-South (CDF-S) and four flanking 250 ks Chandra observations (see Chapter 2 for an extensive discussion of these observations). These Chandra Deep Fields (CDFs) are the most sensitive X-ray surveys yet conducted and are complemented by extensive multiwavelength coverage (e.g., through GALEX, HST, Spitzer, Keck, NOAO, SCUBA, VLA, VLT). The combination of the deep Chandra data from the CDFs and their coincident multiwavelength observations have allowed for effective investigations of galaxy populations selected via morphological type, physical properties, and environment. It is predicted that as galaxy populations assembled (via star-formation and galaxy/galaxy interactions) and aged passively (e.g., through dynamical relaxation, aging of stellar populations, and cooling of hot gas) into the diverse galaxy population that we observe in the local universe, the dominant X-ray properties (e.g., X-ray binaries and hot gas) of normal galaxies correspondingly evolved dramatically. In this thesis, I provide significant new constraints and insight into how the global X-ray properties evolved in response to the physical changes that the galaxy populations underwent. This is achieved through investigations of (1) the X-ray properties and evolution of early-type (E-S0) galaxies over the last half of cosmic time (i.e., since z ~ 0.7; Chapter 3), (2) the demographics and properties of intermediate-redshift (z ~ 0.05-0.3) off-nuclear X-ray sources within normal galaxies (Chapter 4), (3) the X-ray properties and evolution of late-type (Sa-Irr) galaxies over the last ~70% of cosmic history (i.e., since z ~ 1.4; Chapter 5), and (4) the average X-ray properties of distant (z ~3, 4, 5, and 6) Lyman break galaxies and their AGN content (Chapter 6).