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

Citation

Eckart, Megan Elizabeth (2007) Measurements of X-ray selected AGN and novel superconducting X-ray detectors. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-06072007-130804

Abstract

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) caltech.edu
Record Number:CaltechETD:etd-06072007-130804
Persistent URL:http://resolver.caltech.edu/CaltechETD:etd-06072007-130804
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:2508
Collection:CaltechTHESIS
Deposited By: Imported from ETD-db
Deposited On:03 Jul 2007
Last Modified:26 Dec 2012 02:52

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