Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 21 for “"protostars"”.
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Circumstellar environments around the youngest protostars: interferometric observations and modeling
… Array for Research in Millimeter-wave Astronomy. Protostars form through gravitational collapse inside their natal envelopes, and these circumstellar envelopes contain valuable information about the physical processes of star formation. In this thesis, both molecular lines and dust continuum are …
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The role of ambipolar diffusion in the formation of interstellar cloud cores and protostars
The formation of stars is a fundamental unsolved problem in astrophysics. Interstellar molecular clouds, observed to be the birth place of stars, have masses much larger than those of typical stars. Observed densities, temperatures, and strengths of well-ordered magnetic fields imply that magnetic …
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The role of ambipolar diffusion in the formation of interstellar cloud cores and protostars
The formation of stars is a fundamental unsolved problem in astrophysics. Interstellar molecular clouds, observed to be the birth place of stars, have masses much larger than those of typical stars. Observed densities, temperatures, and strengths of well-ordered magnetic fields imply that magnetic …
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The Role of MHD Waves and Ambipolar Diffusion in the Formation of Interstellar Cloud Cores and Protostars
How stars form out of their parent molecular clouds remains an unsolved fundamental problem of theoretical astrophysics. Magnetic fields are the dominant means of support against self-gravity and, therefore, important in regulating the rate at which stars form. We formulate the problem of the …
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The role of magnetic braking and ambipolar diffusion in the formation of interstellar cloud cores and protostars
The means by which parent molecular clouds give birth to stars constitutes a fundamental unsolved problem in astrophysics. Magnetic fields, which dominate thermal-pressure as a source of support against self-gravity in interstellar molecular clouds, are an important regulator of star-formation. We …
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Observations of disks around the youngest protostars: Characterizing frequency, dust properties, and magnetic fields at the earliest times
… star formation. Class 0 objects are the youngest protostars and most embedded in their natal envelopes, and circumstellar disks can form even at this earliest stage of star formation. Less-embedded Class I protostars have cleared part of their surrounding envelope, yet the envelopes enshrouding …
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The effects of ambipolar diffusion, dust, and ultraviolet radiation in the formation of cores and protostars in interstellar molecular clouds
… their application to the formation of cores and protostars in molecular clouds are discussed."
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The Galactic Starburst Region NGC 3603 : exciting new insights on the formation of high mass stars
… form by repeated collisions (coalescence) of protostars of lower masses. Both scenarios bear difficulties which impose strong constrains on the final mass of the young star. To find evidences for or against one of these two theoretical models is a challenging task for observers. First, sites …
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Probing planetary disks: from birth to protoplanets
… disks can grow even at the earliest times of a protostars life (Class 0 phase). These young objects are heavily obscured in their dusty natal envelope and often carry information from the cloud with them (i.e., the local magnetic field). In fact, theoretical studies have shown that these fields …
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Initial Conditions and Collapse of Prestellar Cores
… a special simplified treatment for the created protostars. The hydrodynamical star formation simulation consists of three stages. The pre-collapse stage forms the prestellar cores and drives the velocity and density fields into dynamical equilibrium so that the resulting cores are physically …
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Submillimeter heterodyne spectroscopy of star forming regions
… disk in a sample of nearby high and low mass protostars of varying ages. While these observations are difficult with single dish telescopes, we show the promise of the technique, and report results on 4 sources.
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The formation of population III stars and their effect on cosmological structure in the early universe
… I find that the accretion rates of primordial protostars have been systematically overestimated by previously published work, which has profound implications for later structure formation and the reionization of the universe. Additionally, the presence of a soft ultraviolet background and warm …
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Properties of turbulent star-forming clusters : models versus observations
… the analysis of properties of individual protostars as well as statistical properties of the entire cluster. It is demonstrated that protostellar mass accretion is a highly dynamical and time-variant process. The peak accretion rate is reached shortly after the formation of the …
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Understanding star formation at early stages in the filamentary era
… to be bound to form possible seeds for future protostars. Furthermore, to understand massive star formation, we study the structure and kinematics of nine starless cores in Orion. As two main models about massive star formation, the turbulent core model and the competitive accretion model, …
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Using fusion-product spectroscopy to study inertial fusion implosions, stopping power, and astrophysical nucleosynthesis at OMEGA and the NIF
… relevant to energy generation in brown dwarfs, protostars, and to production of ³He during the Big Bang.
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Astronomical Interferometry at Submillimetre Wavelengths
… for many previous observational results. Many protostars are suspected of having accretion discs. The JCMT-CSO Interferometer has resolved the dust continuum emission on scales of < 100 AU for the sources HL Tau and L1551-IRS 5. An analysis of the visibility curves is presented, showing that …
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Submillimetre Studies of Pre-stellar and Starless Cores in the Ophiuchus, Taurus and Cepheus Molecular Clouds
… L1147/58 and L1228 have a high ratio of cores to protostars; L1251 and L1174 have a low ratio, suggesting that the latter are active sites of star formation, while in the former, star formation proceeds quiescently. Core external pressures are estimated; all but one of our cores are …
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Constraining the Initial Conditions and Final Outcomes of Accretion Processes around Young Stars and Supermassive Black Holes
… of small spatial scales around young stars and protostars and around the supermassive black hole at the galactic center. I begin by describing adaptive optics-fed infrared spectroscopic studies of nascent and newborn binary systems. Binary star formation is a significant mode of star formation …
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The Magnetic Field of Protostar-Disk-Outflow Systems
Recent observations of protostellar cores reveal complex magnetic field configurations that are distorted in the innermost disk region. Unlike the prestellar phase, where the magnetic field geometry is simpler with an hourglass configuration, magnetic fields in the protostellar phase are sculpted …
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