Dissertation/Thesis Abstract

Quasar Structure from Microlensing in Gravitationally Lensed Quasars
by Morgan, Christopher Warren, Ph.D., The Ohio State University, 2008, 165; 10631194
Abstract (Summary)

I analyze microlensing in gravitationally lensed quasars to yield measurements of the structure of their continuum emission regions. I first describe our lensed quasar monitoring program and RETROCAM, the auxiliary port camera I built for the 2.4m Hiltner telescope to monitor lensed quasars.

I describe the application of our Monte Carlo microlensing analysis technique to SDSS 0924+0219, a system with a highly anomalous optical flux ratio. For an inclination angle cos(i)=0.5, I find an optical scale radius log[ rs/cm] = 14.8±0.4. I extrapolate the best-fitting light curves into the future to find a roughly 45% probability that the anomalous image (D) will brighten by at least an order of magnitude during the next decade.

I expand our method to make simultaneous estimates of the time delays and structure of HE1104-1805 and QJ0158-4325, two doubly-imaged quasars with microlensing and intrinsic variability on comparable time scales. For HE1104-1805, I find a time delay of ΔtAB = t A – tB 162±6 days and estimate a scale radius of log[rs/cm] = 15.7±0.5 at 200 nm in the rest frame. I am unable to measure a time delay for QJ0158-4325, but the scale radius is log[rs/cm] = 14.9±0.3 at 300 nm in the rest frame.

I then apply our Monte Carlo microlensing analysis technique to the optical light curves of 11 lensed quasar systems to show that quasar accretion disk sizes at 250 nm are strongly correlated with black hole mass. The resulting scaling relation is consistent with the expectation from thin disk theory, but it implies that black holes radiate with relatively low efficiency. These sizes are also larger, by a factor of approximately 3, than the size needed to produce the observed 800 nm quasar flux by thermal radiation from a thin disk with the same temperature profile.

Finally, I analyze the microlensing of the X-ray and optical emission of the lensed quasar PG 1115+080. I find that the size of the X-ray emission region is approximately 1.3 dex smaller than that of the optical emission, and I find a weak trend supporting models with low stellar mass fractions near the lensed images.

Indexing (document details)
Advisor: Kochanek, Christopher
Commitee: DePoy, Darren, Gould, Andrew
School: The Ohio State University
Department: Astronomy
School Location: United States -- Ohio
Source: DAI-B 78/11(E), Dissertation Abstracts International
Subjects: Astrophysics, Astronomy
Keywords: Accretion, Accretion disks, Dark matter, Gravitational lensing, Quasars: general
Publication Number: 10631194
ISBN: 978-0-355-01474-7
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