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Measurements of X-ray selected AGN and novel superconducting X-ray detectors


Eckart, Megan Elizabeth (2007) Measurements of X-ray selected AGN and novel superconducting X-ray detectors. Dissertation (Ph.D.), California Institute of Technology.


Major astrophysical advances typically come through combining new observational approaches with new technologies. This thesis involves work on both fronts, combining observational work using data from the Chandra X-ray Observatory and Keck Observatory with novel superconducting detector development to further technology for future observatories.

The subject of the first part of this thesis is the Serendipitous Extragalactic X-ray Source Identification (SEXSI) program, a survey using Chandra data selected to probe the dominant contributors to the 2-10 keV cosmic X-ray background. SEXSI covers more than 2 square degrees of sky and employs optical photometric and spectroscopic followup of sources discovered in archival Chandra fields. The resulting sample consists of 1034 hard X-ray-selected sources with R-band optical-followup imaging, and optical spectroscopy for 477 of the sources, filling the gap between wide-area, shallow surveys and the deep, pencil-beam surveys. The vast majority of the 2-10 keV-selected sample are AGN with redshifts between 0.1 and 3. We discuss results from our survey, including the spectroscopic properties of hard X-ray sources and the relationship between X-ray and optical properties of our sources. In addition, we present infrared data from the Spitzer Space Telescope that cover a subset of the Chandra fields, which allows us to explore the relative strengths of Chandra and Spitzer as black-hole finders.

The second part of this thesis focuses on microwave kinetic inductance detectors (MKIDs), a superconducting detector technology that has breakthrough potential for providing megapixel imagers with several eV energy resolution for use in future X-ray missions. These detectors utilize simple, thin-film lithographed microwave resonators as photon detectors in a multiplexed readout approach. X-ray absorption in a superconductor creates quasiparticle excitations, with number proportional to the X-ray energy. The surface impedance of a superconductor changes with the quasiparticle density, and if operated at T << T_c, extremely small changes in the surface impedance can be measured using the thin-film resonant circuit and microwave readout techniques. This provides a sensitive detector with excellent energy resolution.

MKIDs offer the advantage over many other cryogenic detector technologies that they can be easily multiplexed by coupling many resonators to a single microwave transmission line. In addition, the readout electronics can be operated at room temperature, a significant advantage for space applications. The practical application of MKIDs for photon detection requires a method of efficiently coupling the photon energy to the MKID. To this end we have been studying MKIDs in a strip detector architecture. The second part of this thesis presents our results using strip detectors with tantalum absorbers coupled to aluminum MKIDs.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:active galactic nuclei; Chandra surveys; low temperature detectors; microwave kinetic inductance detectors; Spitzer AGN; X-ray background surveys
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Physics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Harrison, Fiona A.
Thesis Committee:
  • Harrison, Fiona A. (chair)
  • Steidel, Charles C.
  • Sari, Re'em
  • Golwala, Sunil
Defense Date:22 May 2007
Author Email:eckart (AT)
Record Number:CaltechETD:etd-06072007-130804
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:2508
Deposited By: Imported from ETD-db
Deposited On:03 Jul 2007
Last Modified:26 Dec 2012 02:52

Thesis Files

PDF (eckart_thesis.pdf) - Final Version
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