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 141 for “"Interstellar Medium"”.
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Turbulence and structure formation in the interstellar medium
The interstellar medium (ISM) structure and dynamics are the result of the interplay between many physical processes such as turbulence, gravity, thermal processes, magnetic fields and cosmic rays which determine the modes of molecular cloud and star formation, and which in turn, define the global …
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Stochastic histories of dust grains in the interstellar medium
… of SUperNOva CONdensateS (SUNOCONS) within the Interstellar Medium (ISM). This is done via a Monte Carlo process where refractory dust grains formed within supernova remnants are subjected to the processes of sputtering and collisional fragmentation in the diffuse phase and accretion within the …
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Interstellar medium properties and star formation in nearby galaxies
We study the properties of the interstellar medium (ISM) of nearby galaxies from The HI Nearby Galaxy Survey (THINGS) by analyzing the shapes of their HI emission velocity profiles. We apply a stacking method to increase the signal-to-noise (S/N) of the profiles and obtain what we call a super …
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The interstellar medium and star formation in edge-on galaxies
… star forming regions and the importance of interstellar gas pressure in controlling the ρH2 /ρHI ratio for two cases: varying and constant velocity dispersions. The Q parameter does not show a clear correlation with massive star formation although Q using varying velocity dispersion shows …
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The Interstellar Medium Along The Life of Sight Toward X Per
I have used ultraviolet, optical, and radio observations of the B0 V star X Per to analyze the physical conditions within the obscuring diffuse cloud. The ultraviolet data are from the International Ultraviolet Explorer satellite, the optical data are primarily blue echelle spectra, and the radio …
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Studies of the Ionised Interstellar Medium at Low Radio Frequencies using LOFAR
… frequencies, their radiation is affected by interstellar propagation effects like dispersion, which causes a frequency-dependent propagation delay that can vary with time when there is relative motion between the Earth, the pulsar and the gas between the two. These effects on the radiation …
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Investigating bursty star formation and interstellar medium conditions in low-mass galaxies
Low-mass galaxies or dwarf galaxies (galaxies with stellar massM∗<10⁹ᐧ⁵.5M⊙) are the most abundant systems in the universe, and are the progenitors of present-day Milky Way-mass galaxies. Compared to massive galaxies, low-mass galaxies exhibit higher specific star formation rates (sSFR), and have …
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Pulse broadening due to multipath scattering of radio waves by the interstellar medium.
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1971.
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On the Chemistry of Molecules Containing Silicon, Phosphorus, and Sulfur in the Interstellar Medium
The Interstellar Medium (ISM) is an extreme environment that requires a wide range of experimental techniques to investigate its many shades. This thesis presents a collection of studies in Laboratory Astrochemistry aimed at providing new experimental data for astrochemical modeling and probing the …
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A numerical investigation of the interaction of the heliosphere with the local interstellar medium
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1998.
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Properties and Kinematics of the Interstellar Medium in a Small Sample of Nearby Dwarf Galaxies
The distribution and kinematics of HI in the dwarf ellipticals NGC 185 and NGC 205 are significantly different from those in giant ellipticals, so that an internal origin for the gas in the dwarf ellipticals should be considered. Finally, the presence of gas in LGS 3 conflicts with evolutionary …
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Investigating the cosmic-ray ionization rate in the galactic interstellar medium through observations of H3+
Observations of H3+ in the Galactic diffuse interstellar medium (ISM) have led to various surprising results, including the conclusion that the cosmic-ray ionization rate (zeta_2) is about 1 order of magnitude larger than previously thought. The present survey expands the sample of diffuse cloud …
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Growth of unsaturated, cyclic, and polycyclic aromatic hydrocarbons: Reactions under the conditions of the interstellar medium
… have been long discussed to be carriers of interstellar infrared (IR) emission and ultraviolet (UV) absorption features. Yet, their origin in dense phases of the interstellar medium (ISM), such as molecular clouds, remains unclear. In this work, growth mechanisms based on ion-molecule …
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Nuclear Spin Dependence in Reactions of Hydrogen (3+) Ion in the Laboratory and the Interstellar Medium
… for understanding the deuterium chemistry of the interstellar medium, and for the fundamental chemical physics of these very simple molecules.
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Exploiting pulsar timing at low radio frequencies: applications to Pulsar Timing Arrays, Interstellar medium and HII regions
… chromatic propagation effects in the ionised interstellar medium and to refine the modelling of noise processes in Pulsar Timing Array (PTA) analyses. A central element of this thesis is the combination of observations from LOFAR and NenuFAR with higher-frequency data from the European PTA …
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Studying the Large Scale Structure and interstellar Medium of Galaxies During the Epochs of Peak Cosmic Star formation and Reionization With Infrared Fine Structure Lines
… (FS) lines from trace metals in the interstellar medium (ISM) of galaxies are valuable diagnostics of the physical conditions in a broad range of astrophysical environments, such gas irradiated by stellar far-ultraviolet (FUV) photons or X-rays from accreting supermassive black holes, …
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Dissociative charge transfer of organic molecules induced by collisions with the He+ cation. A joint experimental and theoretical study of relevance for the interstellar medium evolution
… destruction of complex organic molecules in the interstellar medium (ISM). We have carried out dissociative charge transfer reactions of He+ with two oxygen containing organic molecules, ubiquitous in ISM: dimethyl ether (DME, CH3OCH3 ) and methyl formate (MF, HCOOCH3). Since they have a …
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Quantum Mechanical Study of Spin-Forbidden Reactions in Organometallic Catalysis and Astrochemistry
… in organometallic C-H bond activation and interstellar peptide-bond formation, as well as the derivation of the Morse empirical potential from an electrostatic model. In the first part, the role of triplet electronic state in spin-accelerated iron-catalyzed C(sp2)-H bond activation in …
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