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 35 for “"Interstellar Medium (ISM)"”.
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The HI super profiles of the THINGS galaxies
… galaxies to study the phase structure of the interstellar medium (ISM) and its relation to galaxy properties and morphology. To construct high signal-to-noise (S/N) profiles, we use a method analogous to the stacking method sometimes used in high redshift HI observations. We call these high …
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Self-Similar Models of Quasar Outflow Shock Structures
… structure that shocks and pushes the ambient interstellar medium (ISM) outward. This thesis analyses, combines and expands on existing analytic self-similar models of these structures in the context of quasar accretion disk winds; we then search for the bulk acceleration (positive or negative) …
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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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Small-scale structures in planetary nebulae
… affects the structure and composition of the interstellar medium (ISM) from which the next generation of stars is born. Molecular hydrogen (H[subscript 2]) was used a tracer for molecular emission and its excitation properties used as a probe of shock physics. Previous studies of several …
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Lyα emission as a sensitive probe of galactic mergers and reionization
… to feedback physics and the structure of the interstellar medium (ISM). We identify several Lyα parameters that reliably predict the escape fraction of Lyman continuum (LyC) photons. • What governs the visibility of high-redshift LAEs? We show that galaxy mergers trigger intense starbursts, …
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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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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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X-ray spectroscopy of low-mass X-ray binaries
… edge depths are consistent with the estimated interstellar absorption. The second part of this thesis uses LMXBs as probes of the interstellar medium (ISM).
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Mid-Infrared Studies of Galactic sources: Probing the Relationship Between Polycyclic Aromatic Hydrocarbons and their Physical Environment
… $mu$m have been observed ubiquitously in the interstellar medium (ISM) of Galactic and extragalactic sources. These emission features arise from the vibrational relaxation of polycyclic aromatic hydrocarbons (PAHs) after the absorption of a far-ultraviolet (FUV) photon. PAHs are astronomically …
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Laboratory Studies of Gas-Grain Processes on Cosmic Dust Analogues
<p>The formation of molecules in the interstellar medium (ISM) takes place both in the gas phase and on surfaces of cosmic dust grains. Gas phase reactions alone are found to be insufficient to account for the observed abundance of molecules such as molecular hydrogen, water, carbon dioxide, …
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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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Revisiting polycyclic aromatic hydrocarbon emission in Photodissociation regions
… play a critical role in the evolution of the interstellar medium (ISM) as they drive much of the ISM’s heating and ionization balance. As a result, detailed knowledge of the molecular astrophysics of PAHs, including a thorough understanding of their molecular properties and their interactions …
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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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Studies of TeV Gamma-Ray Sources in the Hydrogen-Alpha Optical Line
… (SNR) G18.7-2.2 is helping us to understand the interstellar medium (ISM) in multiple different wavebands (Voisin et al., 2016). G18.7-2.2 is observed in optical H𝛼, and has a spectral intensity ratio of ionised sulphur to H𝛼 [S II] / H𝛼 indicating that it is a SNR. There is a need to look for …
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The Nature and Origin of Large Scale Diffuse X -Ray Emission in the Large Magellanic Cloud
… the physical structure of the multi-phase interstellar medium (ISM) of supergiant shells in the LMC using LMC2 as a detailed case study because it has the highest X-ray surface brightness of all supergiant shells in the LMC. Neither Halpha nor H I 21-cm line observations of LMC2 show an …
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Dispersion measure variations in pulsar observations with LOFAR
… which describes the turbulence structure of the interstellar medium (ISM). I find that for a number of pulsars results show consistency with the Kolmogorov distribution (e.g. PSRs J1913−0440 and J2157+4017) while other sources show significant difference (e.g. PSRs J0108+6608 and J0614+2229). I …
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Polarized Bow Shock Nebulae Reveal Features of the Winds and Environments of Massive Stars
… When a stellar wind interacts with the local interstellar medium (ISM), if the relative velocity between wind and ISM is supersonic, then a stellar wind bow shock is formed. Bow shocks and related density enhancements produced by the winds of massive stars moving through the interstellar …
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Multi-dimensional simulations of bow shocks of massive, high-velocity runaway stars
… stellar winds ejected by runaway stars and the interstellar medium (ISM). Studying their properties provides constraints on mass-loss rates, stellar wind velocities and the properties of the ISM. In this work, we study the formation of bow shocks from stars at the tail end of the runaway …
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The relation between atomic and molecular gas: the Magellanic Clouds and beyond
… to analyze the spatial correlation of the interstellar gas in molecular and atomic phases and old stellar populations. The results suggest strong independent roles for galaxy metallicity and stellar-to-gas ratios in the atomic-to-molecular gas transition and are consis- tent with a …
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Probing the Gamma-ray Emission from HESS Source RX J1713.7-3946
… to produce 𝛾-rays via interactions with the interstellar medium (ISM) in high energy situations. For this reason 𝛾-rays are often used as a tracer for the parent CRs. The hadronic (𝑝𝑝 interactions) and leptonic processes (IC scattering, synchrotron processes and relativistic Bremsstrahlung) …
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