Since different parts of the Moon display varying magnetic field strengths, our goal was to determine whether these differences are due to specific geological characteristics. We found that older materials tend to be more magnetic than younger materials. Additional statistical studies found that the mare regions of the Moon are less magnetic than the plains and terra regions. We did not find a simple relationship between lunar magnetism and crustal thickness, and this is inconsistent with the hypothesis that thicker crust is more magnetic since there is additional material. Thus, it is not just a matter of the amount of magnetic material that determines the magnetic field strength of the lunar crust. Our results demonstrate that magnetism and crustal thickness have a complex relationship, with multiple distinct groups corresponding to various regions of the Moon. The lunar maria formed a particularly distinct group, consisting of low magnetism and thin crust, while the lunar highlands consist of thick crust but typical magnetic field values. The ejecta thickness and magnetic field distributions for specific craters showed that larger impact basins have a thicker and more widespread ejecta blanket than smaller craters. We did not find a consistent pattern of magnetic field enhancements near specific craters, but evidence for these strong magnetic signatures was present for Mare Crisium and Mare Nectaris. These results may support the hypothesis that ejecta materials are carriers of magnetism, and this may be the reason for their tendency to have higher magnetic field strengths.

Photolithography is a key element of the modem integrated circuit process. It is photolithography, combined with metal deposition, that allows a three dimensional circuit to be built up on a two dimensional surface. Since it is such an important part of the semiconductor manufacturing industry, a massive base of research in this area already exists. The problem with this pre-existing research is that it is geared solely toward industrial purposes, as opposed to more academic research areas. The goal of my research is to move this industrial process into the academic setting of Pomom College.

With experimentation on graphene (an atomic layer of graphite) becoming more and more common it is imperative that we have the capability to shape the material beyond the random manner in which it is deposited by mechanical exfoliation. This capability would be invaluable not only for the interesting electronic and optical properties that can be obtained, but also potentially for characterizing the mechanical resonators that we have been able to fabricate here at Pomona College by suspending few-layer graphene sheets over trenches in SiO2. We propose novel methods for etching graphene that should allow us to shape the material when used in conjunction with our e-beam lithography capabilities.

The question as to whether the distribution of radio loudness in active galactic nuclei (AGN) is actually bimodal has been discussed extensively in the literature. Furthermore, there have been claims that radio loudness depends on black hole mass and Eddington ratio. We investigate these claims using the low redshift broad line AGN sample of Greene & Ho 2007, which consists of 8434 objects at z < 0.35 from the Sloan Digital Sky Survey (SDSS) Fourth Data Release. We obtained radio fluxes from the Very Large Array Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) survey for the SDSS AGN. Out of the 8434 SDSS AGN, 846 have radio emission within 4" of the optical counterpart and are considered to be core emission. We also perform a systematic search for extended emission in FIRST that can be positively associated with the optical counterparts and find 51 out of the 846 previously detected core sources have extended emission that must be taken into account when calculating the total radio luminosity. Further, we find an additional 12 objects that have extended radio emission but no detectable radio core and have classic FR II type morphologies. Using these data, the question of radio bimodality and the dependence of radio-loudness on physical parameters are investigated for different subsets of the total sample. We find modest trends in the radio-loud fraction as a function of black hole mass and Eddington ratio, where the fraction of RL AGN increases for the largest black hole mass group and decreases with increasing Eddington ratio. With extended emission taken into account, we find strong evidence for a bimodal distribution in radio-loudness, where the lower radio luminosity core-only sources appear as a population separate from the extended sources with a dividing line at log(R) = 1.75. This dividing line is interesting in that it requires the radio luminosity to be 50 times the optical luminosity, ensuring that these are indeed the most RL AGN, which may have different or extreme physical conditions in their central engines when compared to the more numerous radio quiet AGN in this sample.

The effect of initial state correlation on high-energy dipole photoionization is considered and it is shown that for almost all atomic electron the asymptotic high-energy dependence is E-7/2, and the dominant transition is an ionization plus excitation satellite transition. This is demonstrated in numerical calculations of the photoionization of Ge4p2 1S and Sn 5p2 1S.

<p> The Kuiper belt is a population of small bodies located outside Neptune's orbit. The observed Kuiper belt objects (KBOs) can be divided into several subclasses based on their dynamical structure. I construct models for these subclasses and use numerical integrations to investigate their long-term evolution. I use these models to quantify the connection between the Kuiper belt and the Centaurs (objects whose orbits cross the orbits of the giant planets) and the short-period comets in the inner solar system. I discuss how these connections could be used to determine the physical properties of KBOs and what future observations could conclusively link the comets and Centaurs to specific Kuiper belt subclasses. </p><p> The Kuiper belt's structure is determined by a combination of long-term evolution and its formation history. The large eccentricities and inclinations of some KBOs and the prevalence of KBOs in mean motion resonances with Neptune are evidence that much of the Kuiper belt's structure originated during the solar system's epoch of giant planet migration; planet migration can sculpt the Kuiper belt's scattered disk, capture objects into mean motion resonances, and dynamically excite KBOs. Different models for planet migration predict different formation locations for the subclasses of the Kuiper belt, which might result in different size distributions and compositions between the subclasses; the high-inclination portion of the classical Kuiper belt is hypothesized to have formed closer to the Sun than the low-inclination classical Kuiper belt. I use my model of the classical Kuiper belt to show that these two populations remain largely dynamically separate over long timescales, so primordial physical differences could be maintained until the present day. </p><p> The current Kuiper belt is much less massive than the total mass required to form its largest members. It must have undergone a mass depletion event, which is likely related to planet migration. The Haumea collisional family dates from the end of this process. I apply long-term evolution to family formation models and determine how they can be observationally tested. Understanding the Haumea family's formation could shed light on the nature of the mass depletion event.</p>

<p> A significant portion of the process of detecting pulsars from radio sky surveys remains a largely manual task. The visual inspection of data in order to detect and validate potential pulsar candidates is by far the most time consuming portion of the overall process. Coupled with the fact that well over a Petabyte of pulsar survey data has been archived, the task of identifying these valuable phenomena is tedious and time consuming.</p><p> Using data from a survey performed with the National Radio Astronomy Observatory&rsquo;s (NRAO&rsquo;s) Green Bank Telescope (GBT) in 2007, this thesis explores the application of machine learning techniques to mitigate the manual efforts involved in pulsar candidate detection. The performance of three different classifiers is explored - Naive Bayes, C4.5 (J48) Decision Tree, and Support Vector Machine. Preprocessing and feature extraction methods are described and a framework for applying the classifiers to the survey data is presented. Multiple features were extracted from the survey data and used to train the classifiers. Cross-validation results of the various feature sets and classifiers are documented. Experiments suggest the potential of the proposed framework in rapidly detecting pulsars from large amounts of survey data.</p>

<p> We utilize a Poisson likelihood in a maximum likelihood statistical analysis to analyze X-ray spectragraphic data. Specifically, we examine four extragalactic supernova remnants (SNR). IKT 5 (SNR 0047-73.5), IKT 25 (SNR 0104-72.3), and DEM S 128 (SNR 0103-72.4) which are designated as Type Ia in the literature due to their spectra and morphology. This is troublesome because of their asymmetry, a trait not usually associated with young Type Ia remnants. We present <i>Chandra X-ray Observatory</i> data on these three remnants, and perform a maximum likelihood analysis on their spectra. We find that the X-ray emission is dominated by interactions with the interstellar medium. In spite of this, we find a significant Fe overabundance in all three remnants. Through examination of radio, optical, and infrared data, we conclude that these three remnants are likely not "classical" Type Ia SNR, but may be examples of so-called "prompt" Type Ia SNR. We detect potential point sources that may be members of the progenitor systems of both DEM S 128 and IKT 5, which could suggest a new subclass of prompt Type Ia SNR, Fe-rich CC remnants. In addition, we examine IKT 18. This remnant is positionally coincident with the X-ray point source HD 5980. Due to an outburst in 1994, in which its brightness changed by 3 magnitudes (corrsponding to an increase in luminosity by a factor of 16) HD 5980 was classified as a luminous blue variable star. We examine this point source and the remnant IKT 18 in the X-ray, and find that its non-thermal photon index has decreased from 2002 to 2013, corresponding to a larger proportion of more energetic X-rays, which is unexpected.</p>

This thesis describes an investigation into weak gravitational lensing, a unique and powerful astronomical tool for the study of dark matter on large scales. Lensing distorts background images, inducing correlations in the observed ellipticities of galaxies, and these correlations can be used to estimate many characteristics of the Universe. Key to all weak lensing studies is a reliable and unbiased method to detect weak lensing distortions from observed galaxy images that are contaminated by Earth and telescope-based shearing and smearing distortions. A new galaxy model-fitting technique is presented that has been developed in order to satisfy this requirement, which will also permit future signal-to-noise optimised measurements of weak lensing shear. Model-fitting provides a good alternative to the standard scite{KSB} method (KSB), and comparisons between the two techniques are drawn from an analysis of deep {it R} band imaging from the COMBO-17 survey, revealing strong evidence for the presence of bias in KSB galaxy shape measurement. With the galaxy model-fitting technique, an investigation into the effectiveness of the Oxford Dartmouth Thirty degree survey (ODT) for gravitational lensing studies is presented, resulting in the detection of weak gravitational lensing by large scale structure, or `cosmic shear', in 0.7 square degrees of the best seeing ODT images. One concern for all cosmic shear studies is that the weak lensing signal, manifest in the weakly correlated ellipticities of distant galaxies, is contaminated by the intrinsic alignment of close galaxy pairs, potentially induced during galaxy formation by physical interactions such as tidal forces. This contamination is investigated theoretically, through numerical simulations, and observationally, with an analysis of the COMBO-17 survey and the study of published results from the Red-sequence Cluster survey and the VIRMOS-DESCART survey, concluding that the intrinsic alignment effect is at the lower end of the range of theoretical predictions. The impact of intrinsic galaxy alignments on cosmological parameter estimation is investigated, with an analysis of the weak lensing results from the COMBO-17 survey. When marginalising over the observationally constrained intrinsic alignment signal, the amplitude of the matter power spectrum sigma_8 is reduced by ~0.03 to sigma_8(Omega_m / 0.27)^{0.6} = 0.71 pm 0.11, where Omega_m is the matter density parameter. With distance information from either spectroscopy or photometric redshifts, the down-weighting of nearby galaxy pairs in weak lensing analysis can be optimised to virtually eliminate the systematic errors in the shear signal arising from intrinsic galaxy alignments, leaving a much smaller, largely statistical error. This method is applied to the photometric redshift sample of the COMBO-17 survey. Weak lensing measurements from the forthcoming SuperNova/Acceleration Probe weak lensing survey (SNAP), and the Canada-France-Hawaii Telescope Legacy survey, are expected to be contaminated on scales >1 arcminute by intrinsic alignments at the level of ~ 1% and ~2% respectively. Division of the SNAP survey for lensing tomography significantly increases the contamination in the lowest redshift bin to ~7% and possibly higher. Removal of the intrinsic alignment effect by the downweighting of nearby galaxy pairs will therefore be vital for the lensing tomography studies of SNAP.

Over the past decade the luminescence properties of sapphire (∝-AL2O3) and ruby (Al2O3:Cr2O3) have been the subject of many investigations because of their importance in materials technology. Sapphire and ruby are at present used as lasing materials, radiation dosimeters, and as optical windows. In order that these operations may be made more efficient, and that other useful luminescent properties may be systematically explored and developed, much attention has been given to understanding the luminescent mechanisms from the standpoint of the physics of the solid state. However, mechanisms have not yet been proposed that describe in detail the known luminescent properties of sapphire and ruby. The luminescence experiments which have been previously reported in the literature on sapphire and ruby fall into two classes: experiments in which the exciting energy is stored in the crystal by some defect mechanism and subsequently released by perturbing the crystal, and experiments in which the luminescence is observed while the crystals are being excited. Thermoluminescence, in which energy is stored in the crystals by exposing it to ionizing radiation and subsequently released by raising the temperature of the crystal, is the most extensively used technique of the former class. The facts concerning the thermoluminescence of sapphire and ruby are well documented. (11,12) Numerous experiments in the latter class have been reported in which the exciting radiation was in the visible or ultraviolet energy region. (16, 17) These latter experiments have a disadvantage; the amount of exciting energy absorbed is not independent of two important parameters, temperature and chromium concentration. It was the primary intent of these investigations to resolve the difficulty of the dependence of the absorbed energy by exciting sapphire and ruby crystals with x-rays. Because the energy of the x-ray photons incident on and within the crystal is more than an order of magnitude more energetic than is necessary to produce highly mobile or free electrons within the crystal, the number of such electrons produced is independent of the temperature and chromium concentration over the range that these parameters were varied. The program of experiments reported herein was designed to answer the following questions: (1) How does the intensity of the total luminescence depend on the temperature? (2) How does the emission spectrum depend on temperature and chromium concentration? (3) How does the luminesce yield depend on temperature? The answers to these questions were obtained by observing the luminescence of sapphire and ruby, subjected to continuous x-ray excitation, as a function of temperature and chromium concentration. The total x-ray-induced luminescence and emission spectra of two crystals, one nominally pure sapphire and the other sapphire containing 0.005% Cr2O3, were observed as the temperature of the crystals was raised and lowered between 25°C and 400°C. The results for other chromium concentrations (0.05% and 0.5% Cr2O3) may be found in Mr. Wayne Cooke’s masters’ thesis (21) The thermoluminescence total emission and emission spectra were observed between 25°C and 400°C after x-ray exposure at room temperature. It should be noted that there is one experiment in the literature in which the x-ray-induced luminescence of ruby was observed as a function of temperature.(19) The investigators observed the luminescence as the temperature increased; hence, much of the emission as the temperature decreases because the energy stored in a crystal at a particular temperature has a decreasing probability of being released at lower temperatures.