Investigation of Energy-Dependent Morphology in Pulsar Wind Nebulae
Date of Award
Doctor of Philosophy (PhD)
Observations of TeV gamma rays enable investigation of extreme, high-energy astrophysical environments. Of the identified TeV sources within the Galaxy, the largest number are pulsar wind nebulae (PWNe), formed by the shocked wind of relativistic leptons emitted by a pulsar and confined by the surrounding medium, with broadband emission arising from synchrotron and inverse Compton mechanisms. PWNe exhibit a wide range of morphologies as a result of a complex evolution, depending on the properties of the parent pulsar and confining medium.
This work describes the discovery of gamma-ray emission from the PWN within the supernova remnant (SNR) CTA 1 by the VERITAS telescope array. By imaging the Cherenkov light from gamma-ray induced atmospheric showers, VERITAS revealed an extended TeV nebula surrounding the pulsar PSR J0007+7303. Comparison of the observed properties with known PWN, along with a one-zone model, suggests a recent interaction with the SNR reverse shock and allows for an estimate of the average nebular magnetic field strength. No significant energy-dependent morphology is seen.
A multi-zone, cylindrically symmetric model is created to investigate tailed-out PWN morphology, accounting for multiple mechanisms for particle transport and cooling. The model is applied to the CTA 1 data, with a limited search of the parameter space performed to fit the observed spectrum and extent. Possible improvements to the model performance are discussed.
Chair and Committee
Roger Chamberlain, Francesc Ferrer, Martin Israel, Henric Krawczynski, Lee Sobotka
McArthur, Steven, "Investigation of Energy-Dependent Morphology in Pulsar Wind Nebulae" (2012). Arts & Sciences Electronic Theses and Dissertations. 284.