We study the abundance of substructure in the matter density near galaxies using ALMA Science Verification observations of the strong lensing system SDP. 81. We present a method to measure the abundance of subhalos around galaxies using interferometric observations of gravitational lenses. Using simulated ALMA observations we explore the effects of various systematics, including antenna phase errors and source priors, and show how such errors may be measured or marginalized. We apply our formalism to ALMA observations of SDP. 81. We find evidence for the presence of a M = 10(8.96 +/- 0.12)M(circle dot) subhalo near one of the images, with a significance of 6.9 sigma in a joint fit to data from bands 6 and 7; the effect of the subhalo is also detected in both bands individually. We also derive constraints on the abundance of dark matter (DM) subhalos down to M similar to 2 x 10(7) M-circle dot, pushing down to the mass regime of the smallest detected satellites in the Local Group, where there are significant discrepancies between the observed population of luminous galaxies and predicted DM subhalos. We find hints of additional substructure, warranting further study using the full SDP. 81 data set (including, for example, the spectroscopic imaging of the lensed carbon monoxide emission). We compare the results of this search to the predictions of Lambda CDM halos, and find that given current uncertainties in the host halo properties of SDP. 81, our measurements of substructure are consistent with theoretical expectations. Observations of larger samples of gravitational lenses with ALMA should be able to improve the constraints on the abundance of galactic substructure.

Pines’ and Gottlieb’s Formulations for the gravitational potential provides expressions for the gravitational potential, U, and its derivatives in a co-ordinate system that produces non-singular values. This report summarizes the origin of the singularities due to the spherical co-ordinate system and a discussion of the methods by which the singularity produced by the conventional representation of the gravitational potential is removed by the implementations described in this report. / text

Thesis (M.S. in physics)--Washington State University, December 2008. / Title from PDF title page (viewed on June 19, 2009). "Department of Physics and Astronomy." Includes bibliographical references (p. 44-46).

Thesis (Ph. D.)--University of Texas at Austin, 1998. / Vita. Includes bibliographical references (leaves 175-187). Available also in a digital version from Dissertation Abstracts.

Thesis (M.S.)--Brigham Young University. Dept. of Physics and Astronomy, 2006. / Includes bibliographical references (p. 83-84).

Resumo: Neste trabalho é feito o estudo do fenômeno da captura gravitacional temporária e do conceito de esfera de influência, considerando o papel da velocidade relativa. Este estudo foi feito através de simulações numéricas do problema circular restrito de três corpos e através do monitoramento da energia do problema de dois corpos. No caso da captura gravitacional temporária nós acompanhamos a variação de energia do problema de dois corpos (partícula-corpo secundário), de uma partícula que sofre um encontro próximo com um corpo massivo (um planeta, por exemplo). A evolução dessa energia mostra se a partícula foi capturada, ou não, para algumas condições iniciais específicas. Este procedimento resultou na obtenção de funções matemáticas que permitem o cálculo do chamado raio de captura em função da velocidade relativa. No estudo numérico da esfera de influencia, a variação da energia do problema de dois corpos no tempo também foi acompanhada, mas desta vez nós acompanhamos a energia do problema partícula-corpo central, para uma partícula que sofre um encontro próximo com o corpo secundário. A evolução desta energia mostra se a partícula foi afetada significativamente, ou não, pela influência gravitacional do corpo secundário, para condições iniciais específicas. Este procedimento resulta na obtenção de funções matemáticas que permitem o cálculo do raio da esfera de influência em função da velocidade relativa. Finalmente, a manobra de swing-by foi aplicada no estudo do caso dos asteróides Vesta e Magnya com o objetivo de explicar sua distante localização orbital em relação aos demais membros da família do asteróide Vesta. Este estudo mostrou que uma mudança na órbita do Magnya não seria proporcionada apenas pelo swing-by, e que ele deveria sofrer a ação de outros mecanismos para causar tal mudança. / Abstract: This work studies the phenomenom of the temporary gravitational capture and the concept of sphere of influence, taking into account the relative velocity. It has been done through numerical simulations of the restricted three-body problem, and through the analysis of the two-body energy. In the case of the temporary gravitational capture we followed the temporal variation of the two-body energy (particle-secondary body) of a particle that suffers a close enconter with a massive body (a planet, for instance). The evolution of such energy shows if the particle was captured or not, for some specific initial conditions. This procedure results in mathematical functions to calculate the so called capture radius as a function of the relative velocity. In the numerical study of the sphere of influence, we also followed the temporal variation of the two-body energy but, at this time, we followed the energy particle-central body of a particle that suffers a close encounter with a massive body (called secondary body). The evolution of such energy shows if the particle was significantly affected by the gravitational influence of the secondary body or not, for some specific initial conditions. This procedure results in mathematical functions to calculate the sphere of influence as a function of the relative velocity. Finally, the swing-by maneuver was applied in the study of the case of the asteroids Vesta and Magnya, in order to explain its distant orbital localization relative to the localization of the others members of the Vesta's family. This study showed that a change in the orbit of Magnya would not be proporcioned only by the swing-by, and that the asteroid Magnya should suffer the action of others mechanisms to cause it. / Orientador: Othon Cabo Winter. / Coorientador: Antonio Fernando B. de A. Prado. / Banca: Ernesto Vieira Neto. / Banca: Roberto Vieira Martins. / Mestre

This thesis is concerned with developing new methods for performing weak gravitational lensing with the aim of addressing specific systematic effects in weak lensing surveys. The first of these effects is the multiplicative biases which arise as a result of isotropic smearing. This smearing may be due to atmospheric seeing or an instrumental PSF. Isotropic smearing circularizes a galaxy image and leads to a systematic under-estimate of the modulus of the observed ellipticity. The orientation of the observed galaxy is, however, unaffected. We exploit this property by formulating a weak lensing shear estimator that requires measurements of galaxy position angles only, thereby avoiding the contribution from this systematic. We demonstrate the method on simulations and the CFHTLenS data by reconstructing convergence maps and comparing the results with the standard full ellipticity based approach. We show that the difference between the reconstructed maps for the two approaches is consistent with noise in all of the tests performed. We then apply the technique to the GREAT3 challenge data using three distinct methods to measure the position angles of the galaxies. For all three methods, we find that the position angle-only approach yields shear estimates with a performance comparable with current well established shape based techniques. The second effect addressed arises from the intrinsic alignment of the source galaxies. This alignment mimics a shear signal, and hence biases estimates of the shear. To mitigate this effect, we develop three shear estimators that include polarization information from radio observations as a tracer of a galaxy’s intrinsic orientation. In addition to the shear estimator, we also develop estimators for the intrinsic alignment signal. We test these estimators by successfully reconstructing the shear and intrinsic alignment auto and cross-power spectra across three overlapping redshift bins.

Direct detection of gravitational waves is opening a new window onto our universe. Here, we study the sensitivity to continuous-wave strain fields of a kg-scale optomechanical system formed by the acoustic motion of superfluid helium-4 parametrically coupled to a superconducting microwave cavity. This narrowband detection scheme can operate at very highQ-factors, while the resonant frequency is tunable through pressurization of the helium in the 0.1-1.5 kHz range. The detector can therefore be tuned to a variety of astrophysical sources and can remain sensitive to a particular source over a long period of time. For thermal noise limited sensitivity, we find that strain fields on the order of h similar to 10(-23)/root Hz are detectable. Measuring such strains is possible by implementing state of the art microwave transducer technology. Weshow that the proposed system can compete with interferometric detectors and potentially surpass the gravitational strain limits set by them for certain pulsar sources within a few months of integration time.

The most promising technique for the direct, ground-based detection of gravitational waves is the use of advanced interferometric gravitational wave detectors. These detectors use long-baseline Michelson interferometers, where the critical enabling component is the laser. The laser required for these interferometers must provide a low noise, single frequency, diffraction limited, high power TEM₀₀ beam. Very importantly, the laser beam must be available continuously and without the need for operator intervention. In this thesis I describe the development and characterisation of injection-locked 10 W Nd:YAG lasers, designed specifically for use at the Australian Consortium for Interferometric Gravitational Astronomy (ACIGA) High Power Test Facility (HPTF) in Western Australia, and on the Japanese TAMA 300 gravitational wave interferometer (GWI). The starting point was a 5 W laboratory laser that had demonstrated the proof-of-principle; however this laser had insufficient power, inadequate reliability, and was not suitable for deployment to a remote site. I describe the development of this laser technology and design to realise reliable, longterm operation and field deployability, while satisfying the requirements for a GWI, with the final laser system bearing little resemblance to the proof-of-principle system. Injection-locked lasers were successfully installed at the ACIGA HPTF and at TAMA 300 in June 2004 and September 2005 respectively. The 10 W laser uses a Nd:YAG Coplanar Pumped Folded Slab (CPFS) gain medium. The slab is side-pumped using a temperature controlled, fast-axis collimated, custom laser diode array, and conduction cooled in the orthogonal direction. Interferometry is used to measure the thermal lensing within the gain medium; these measurements are used to design a single-mode, travelling-wave slave resonator. The entire slave laser is temperature controlled and mounted on an integrated, air-cooled base. The thermal design is validated by extensive thermal testing. Long-term and robust injection-locking is achieved by using a servo system based on the Pound-Drever-Hall technique. I describe the development of a split feedback servo system to provide increased frequency stabilisation loop bandwidth and show that long-term injection-locking of the slave laser to a low power non-planar ring oscillator (NPRO) master laser produces a single frequency output at ~ 10 W with M²[subscript]x.y approx ≤ 1.1. Finally, the noise of the injection-locked laser is characterised. Relative intensity noise measurements demonstrate stability comparable to current GWI laser sources, while the results of a heterodyne beat measurement show that the 10 W injectionlocked laser output has frequency noise limited by the NPRO input. The laser installed at the ACIGA HPTF has been used to investigate the effects of increased intracavity laser powers on next-generation interferometers, with the laser described in this thesis being the key enabling component of this research. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1349763 / Thesis (Ph.D.) - University of Adelaide, School of Chemistry and Physics, 2009

The most promising technique for the direct, ground-based detection of gravitational waves is the use of advanced interferometric gravitational wave detectors. These detectors use long-baseline Michelson interferometers, where the critical enabling component is the laser. The laser required for these interferometers must provide a low noise, single frequency, diffraction limited, high power TEM₀₀ beam. Very importantly, the laser beam must be available continuously and without the need for operator intervention. In this thesis I describe the development and characterisation of injection-locked 10 W Nd:YAG lasers, designed specifically for use at the Australian Consortium for Interferometric Gravitational Astronomy (ACIGA) High Power Test Facility (HPTF) in Western Australia, and on the Japanese TAMA 300 gravitational wave interferometer (GWI). The starting point was a 5 W laboratory laser that had demonstrated the proof-of-principle; however this laser had insufficient power, inadequate reliability, and was not suitable for deployment to a remote site. I describe the development of this laser technology and design to realise reliable, longterm operation and field deployability, while satisfying the requirements for a GWI, with the final laser system bearing little resemblance to the proof-of-principle system. Injection-locked lasers were successfully installed at the ACIGA HPTF and at TAMA 300 in June 2004 and September 2005 respectively. The 10 W laser uses a Nd:YAG Coplanar Pumped Folded Slab (CPFS) gain medium. The slab is side-pumped using a temperature controlled, fast-axis collimated, custom laser diode array, and conduction cooled in the orthogonal direction. Interferometry is used to measure the thermal lensing within the gain medium; these measurements are used to design a single-mode, travelling-wave slave resonator. The entire slave laser is temperature controlled and mounted on an integrated, air-cooled base. The thermal design is validated by extensive thermal testing. Long-term and robust injection-locking is achieved by using a servo system based on the Pound-Drever-Hall technique. I describe the development of a split feedback servo system to provide increased frequency stabilisation loop bandwidth and show that long-term injection-locking of the slave laser to a low power non-planar ring oscillator (NPRO) master laser produces a single frequency output at ~ 10 W with M²[subscript]x.y approx ≤ 1.1. Finally, the noise of the injection-locked laser is characterised. Relative intensity noise measurements demonstrate stability comparable to current GWI laser sources, while the results of a heterodyne beat measurement show that the 10 W injectionlocked laser output has frequency noise limited by the NPRO input. The laser installed at the ACIGA HPTF has been used to investigate the effects of increased intracavity laser powers on next-generation interferometers, with the laser described in this thesis being the key enabling component of this research. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1349763 / Thesis (Ph.D.) - University of Adelaide, School of Chemistry and Physics, 2009