Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
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Item The interplay between the central engine and the circumnuclear environment in Compton-thin AGN(Montana State University - Bozeman, College of Letters & Science, 2022) Chalise, Sulov; Chairperson, Graduate Committee: Anne Lohfink; This is a manuscript style paper that includes co-authored chapters.All massive galaxies harbor a supermassive black hole (SMBH) at their galactic center. If these SMBH are actively feeding then they are called Active galactic nuclei (AGN). Their accretion system contains a corona, an accretion disk and an axisymmetric dusty torus. The torus can be connected physically and dynamically to the circumnuclear disk of the galaxy which acts as a molecular gas reservoir for material to be accreted onto the SMBH. Further, AGN can emit radiation from radio up to the gamma rays. The AGN accretion disk emits photons mostly in the optical/UV band which are Compton up-scattered in the corona to generate X-rays. If present, a jet can produce additional high-energy and Synchrotron emission. In some AGN, a huge amount of material can be stripped away from the accretion disk creating an outowing wind. These --radiation pressure, jet, wind etc.--inject energy back into the host galaxy, regulating the SMBH growth. There exist a complex interplay between the AGN feeding and feedback. Understanding this interaction between the central engine and its circumnuclear environment is vital in context of galaxy evolution. My work aims to study this interaction in low to moderately obscured (or Compton-thin) AGN using their broadband multi-epoch X-ray spectra plus other emission bands whenever appropriate. From the spectral analysis of broad-line radio galaxy 3C 109, I was able to constrain its high-energy cutoff for the first time. In another Seyfert galaxy Mrk 926, I was able to explore the origin of its soft excess, and found that a warm coronal origin was slightly preferred. Finally, I performed a joint multi-wavelength analysis with a physical torus model of a sample of Polar-scattered Seyfert 1 galaxies. I utilized their multi-epoch broadband X-ray spectra along with their infrared spectral/photometric data, and was able to constrain their torus properties. Despite being a sample of similar moderately-inclined Compton-thin AGN, I found a complex and varied distribution of gas and dust in their torus.Item Immersions of surfaces(Montana State University - Bozeman, College of Letters & Science, 2022) Howard, Adam Jacob; Co-chairs, Graduate Committee: David Ayala and Ryan GradyTo determine the existence of a regular homotopy between two immersions, f, g : M --> N, is equivalent to showing that they lie in the same path component of the space Imm(M, N). We identify the connected components, pi 0 Imm(W g, M), of the space of immersions from a closed, orientable, genus-g surface W g into a parallelizable manifold M. We also identify the higher homotopy groups of Imm(W g, M) in terms of the homotopy groups of M and the Stiefel space V 2 (n). We then use this work to characterize immersions from tori into hyperbolic manifolds as self covers of a tubular neighborhood of a closed geodesic up to regular homotopy. Finally, we identify the homotopy-type of the space of framed immersions from the torus to itself.Item Rotation sets of flows on higher dimensional tori(Montana State University - Bozeman, College of Letters & Science, 2001) Dumonceaux, Doreen NormaItem L-cuts for genus two translation surfaces(Montana State University - Bozeman, College of Letters & Science, 2013) Bouwman, Andrew Kevin; Chairperson, Graduate Committee: Jaroslaw KwapiszA connected sum is a topological way of joining two Riemann surfaces which results in another surface. It is used in the classification of all connected closed orientable surfaces as being homeomorphic to either the sphere, or a connected sum of tori. The reverse operation, here referred to as a splitting, decomposes a surface as a connected sum. It was recently shown by Curtis McMullen that any translation surface of genus two can be written in infinitely many ways as a connected sum of two flat tori. His method was to find a certain straight saddle connection J, and perform a splitting along J U eta(J), where eta is the hyperelliptic involution (the unique degree-two automorphism on the surface which fixes exactly six points). In this dissertation, we give an elementary argument for existence of such J and show that for all surfaces of genus two on which the vertical flow is minimal, the same kind of splitting is possible along a parallel pair of paths with the straight saddle connection replaced by an L-cut: a broken line with one horizontal and one vertical segment. As a direct consequence of this L-cut splitting, it is shown that a homeomorphism on a genus-two surface which is conjugated to a hyperbolic toral automorphism restricted to an invariant subset (if any such situation even exists) can only be pseudo-Anosov with non-orientable foliations. This makes progress toward addressing an old question of Stephen Smale about the existence of an invariant set of a hyperbolic toral automorphism which is itself a compact surface.