Thesis (PhD) -- University of Western Sydney, Nepean, 1999. / "A thesis submitted for the degree of Doctor of Philosophy at the University of Western Sydney Nepean" "July, 1999" Bibliography : p. 177-185.

No description available.

We present maps of the Large and Small Magellanic Clouds from combined South Pole Telescope (SPT) and Planck data. The Planck satellite observes in nine bands, while the SPT data used in this work were taken with the three-band SPT-SZ camera, The SPT-SZ bands correspond closely to three of the nine Planck bands, namely those centered at 1.4, 2.1, and 3.0 mm. The angular resolution of the Planck data ranges from 5 to 10 arcmin, while the SPT resolution ranges from 1.0 to 1.7 arcmin. The combined maps take advantage of the high resolution of the SPT data and the long-timescale stability of the space-based Planck observations to deliver robust brightness measurements on scales from the size of the maps down to similar to 1 arcmin. In each band, we first calibrate and color-correct the SPT data to match the Planck data, then we use noise estimates from each instrument and knowledge of each instrument's beam to make the inverse-variance-weighted combination of the two instruments' data as a function of angular scale. We create maps assuming a range of underlying emission spectra and at a range of final resolutions. We perform several consistency tests on the combined maps and estimate the expected noise in measurements of features in them. We compare maps from this work to those from the Herschel HERITAGE survey, finding general consistency between the data sets. All data products described in this paper are available for download from the NASA Legacy Archive for Microwave Background Data Analysis server.

Supersoft and quasisoft X-ray sources are collectively known as Very Soft X-ray Sources (VSSs) characterized by their considerably lower effective temperatures than normal X-ray emitting objects and the lack of significant emission above 1 keV, with measured temperatures ranging from about tens to less than about 300 eV, respectively. They are defined observationally and believed to be associated with a wide variety of astrophysical systems such as white dwarfs, neutron stars, and black holes. VSSs have been identified in our own Galaxy, the Magellanic Clouds, and other external galaxies. Due to the vicinity of the Magellanic Clouds and the low associated absorption of soft X-ray photons, they are unique in the studies of VSSs. However, no attempt has been made to search for VSSs and investigate the source population in the Magellanic Clouds using all the available archival data. A systematic survey of VSSs in the Magellanic Clouds was therefore performed using data from both XMM-Newton and Chandra. VSSs were identified by selection algorithim based on X-ray hardness ratio after the background galaxies and foreground stars were filtered. A total of 47 new supersoft and 75 new quasisoft candidates were identified. Six of them were strong enough for spectral analysis with derived temperatures of 15 – 250 eV and luminosities of of 3.5 ×?10?^34– 5.4 ×?10?^36 erg s^(-1). The softest and brightest candidate represents a promising supersoft candidate with a possible UV counterpart identified with XMM-Newton Optical Monitor having an estimated UV luminosity of ~2.7 ×?10?^35 erg s^(-1). The large dataset also allows the long-term studies of some of the previously identified supersoft X-ray sources. Through the comprehensive survey with multi-epoch data, an X-ray/UV stellar flare was discovered and its analysis is also reported. / published_or_final_version / Physics / Master / Master of Philosophy

This thesis is an observational investigation into the origin of large-scale coherent magnetic fields in the Milky Way and the Magellanic Clouds. I use Faraday rotation measure of both polarized extragalactic sources and that derived from diffuse polarized synchrotron emission as probes of interstellar magnetism. Rotation measure uniquely provides the magnetic field direction in the diffuse interstellar medium, which cannot be achieved using other observing techniques. Using extragalactic source rotation measures behind the Small Magellanic Cloud (SMC), I find a large-scale coherent magnetic field in this irregular galaxy, where the classic dynamo effect is expected to be weak. I suggest that the cosmic-ray driven dynamo, which relies heavily on cosmic ray pressure to generate poloidal fields could be in operation. By analyzing rotation measures derived from diffuse polarized emission from the Large Magellanic Cloud (LMC) simultaneously with rotation measures of 100 extragalactic sources behind it, I conclude that the LMC has a quadrupolar-type magnetic field structure, in accord with predictions from dynamo theories. However, the field amplification time scale of a classic dynamo is too long compared to frequent tidal-triggered star forming episodes experienced by the LMC which can prevent any large-scale coherent field from building up. I propose that the cosmic-ray driven dynamo, which has a much shorter amplification time scale than the classic dynamo, could be the origin of the observed coherent fields in the LMC. The dynamo theory predicts a symmetric vertical magnetic field across the galactic disk for Milky Way-type galaxies. However, based on rotation measures of 1,000 extragalactic sources toward the Galactic poles, I find a lack of vertical field symmetry across the Galactic mid-plane. I suggest that the observed RMs could be the superposition of a symmetric disk field and an anti-symmetric field produced by a separate dynamo effect in the Galactic halo. Furthermore, I demonstrate that existing Galactic halo magnetic field models cannot successfully reproduce extragalactic rotation measures at mid-Galactic latitudes in the second Galactic quadrant. I propose that halo fields consist of magnetic spirals could potentially account for the observed RM pattern. / Astronomy

Thesis (Ph.D.)--McMaster University (Canada), 1993. / Source: Dissertation Abstracts International, Volume: 54-12, Section: B, page: 6248. Adviser: D. L. Welch.

Thesis (PhD) - Swinburne University of Technology, 2008. / A dissertation presented in fulfillment of the requirements for the degree of Doctor of Philosophy, Swinburne University of Technology - 2008. Typescript. Bibliography: p. 133-145.

The Magellanic Clouds have long provided a rich celestial laboratory for many astrophysical research programmes. Their location relatively close to the Earth and away from the plane of our Galaxy has made them a natural target for Southern Hemisphere ground-based instrumentation. Likewise, the continuing quest for images of the Clouds with higher dynamic range and improved angular resolution has driven a continual improvement in instrumentation across a range of wavelength bands. The cornerstone of this thesis is a study of selected sources in the Magellanic Clouds. The sample was chosen from the 843MHz Molonglo Observatory Synthesis Telescope survey of the Clouds, based on the existing knowledge of each source, its flux density and angular extent. This sample was used to explore observational and analysis techniques with the Australia Telescope Compact Array in order to better determine the nature of these objects and to identify those sources worthy of further study. This work highlights many pertinent issues associated with the correct classification of sources when only a limited amount of data is available. These issues led directly to the development of a more systematic approach in the classification of the Large Magellanic Cloud source sample, detailed for the first time in this thesis. Two supernova remnants in the Small Magellanic Cloud were studied in detail. The Australia Telescope images of 1E0102.2-7219 revealed, for the first time, the radio structure of this young oxygen-rich supernova remnant, and allowed a detailed comparison with existing optical and X-ray data to be undertaken. The comparisons presented in this thesis and in an earlier publication have prompted exciting new X-ray observations at unprecedented angular resolution. The second, 0101-7226, studied as part of an international collaboration, has a shell morphology at radio wavelengths but no associated X-ray emission and is therefore something of an enigma.

The Magellanic Clouds have long provided a rich celestial laboratory for many astrophysical research programmes. Their location relatively close to the Earth and away from the plane of our Galaxy has made them a natural target for Southern Hemisphere ground-based instrumentation. Likewise, the continuing quest for images of the Clouds with higher dynamic range and improved angular resolution has driven a continual improvement in instrumentation across a range of wavelength bands. The cornerstone of this thesis is a study of selected sources in the Magellanic Clouds. The sample was chosen from the 843MHz Molonglo Observatory Synthesis Telescope survey of the Clouds, based on the existing knowledge of each source, its flux density and angular extent. This sample was used to explore observational and analysis techniques with the Australia Telescope Compact Array in order to better determine the nature of these objects and to identify those sources worthy of further study. This work highlights many pertinent issues associated with the correct classification of sources when only a limited amount of data is available. These issues led directly to the development of a more systematic approach in the classification of the Large Magellanic Cloud source sample, detailed for the first time in this thesis. Two supernova remnants in the Small Magellanic Cloud were studied in detail. The Australia Telescope images of 1E0102.2-7219 revealed, for the first time, the radio structure of this young oxygen-rich supernova remnant, and allowed a detailed comparison with existing optical and X-ray data to be undertaken. The comparisons presented in this thesis and in an earlier publication have prompted exciting new X-ray observations at unprecedented angular resolution. The second, 0101-7226, studied as part of an international collaboration, has a shell morphology at radio wavelengths but no associated X-ray emission and is therefore something of an enigma.

Thesis (Ph. D.)--University of Chicago, Department of Astronomy & Astrophysics, June 2002. / Includes bibliographical references. Also available on the Internet.