Made available in DSpace on 2014-06-11T19:22:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-03-04Bitstream added on 2014-06-13T20:28:59Z : No. of bitstreams: 1 huamanespinoza_m_me_guara.pdf: 968832 bytes, checksum: d9143c9ac2bced7e7e596dfec1f9845b (MD5) / Encontros próximos com asteroides massivos são conhecidos por ser um mecanismo de mobilidade dinâmica que pode alterar significativamente elementos próprios de corpos menores, e eles são a principal fonte de mobilidade dinâmica para asteroides médios e grandes dimensões (D>20 km, aproximadamente). A mobilidade orbital causada pelos encontros próximos com asteroides massivos foi estudado no passado e pode ser um mecanismo viável para produzir a localização atual orbital de alguns dos asteroides tipo V atualmente fora da família Vesta. É bem conhecido, no entanto, que as frequências próprias da precessão do pericentro g e longitude do nodo s de planetas terrestres mudam quando um ou mais dos outros planetas não é considerado no esquema de simulação. Por exemplo as frequências g4 e s4 são diferentes quando o sistema solar completo é considerado ou quando somente Marte e os planetas jovianos foram contabilizadas. Neste trabalho consideramos os efeitos de que a inclusão de um ou mais asteroides massivos no esquema de simulação tiver na órbita dos asteroides massivos e, indirectamente, sobre as estatísticas de mudanças no semieixo maior causada pelos encontros próximos com este asteroide massivo. Nós descobrimos que os asteroides massivos, as frequências próprias são dependentes do número de outros asteroides massivos considerados no esquema de simulação e que, como resultado, as estatísticas inteiras do encontros com asteroides massivos também é afetada. As variações da mudança no semieixo maior próprio a causada pelos quatro asteroides mais massivos variou de até 36,3% nos cinco esquemas de simulações que utilizamos, e o número de encontros que causou a fortes mudanças na semieixo maior variou até um fator de 2. O efeito indireto causado pela presença de outros asteroides massivos, portanto... / Close encounters with massive asteroids are known to be a mechanism of dynamical mobility that can significantly alter proper elements of minor bodies, and they are the main source of dynamical mobility for medium-sized and large asteroids (D>20 km, approximately). Orbital mobility caused by close encounters with massive asteroids has been studied in the past and could be a viable mechanism to produce the current orbital location of some of the V-type asteroids currently outside the Vesta family. It is well known, however, that the proper frequencies of precession of pericenter g and longitude of the node s of terrestrial planets change when one or more of the other planets is not considered in the integration scheme. For instance, the g4 and s4 frequencies are different when the full solar system is considered or when only Mars and the Jovian planets are accounted for. In this work we consider the effect that including one or more massive asteroids in the integration scheme has on the massive asteroids orbit, and, indirectly on the statistics of changes in semi-major axis caused by close encounters with this com mais de ummassive asteroid. We find that massive asteroid proper frequencies are dependent on the number of other massive asteroids considered in the integration scheme and that, as a result, the whole statistics of encounters with asteroid is also affected. Variances of the change in proper a caused by the four most massive asteroids varied up to 36.3% in the five integration schemes that we used, and the number of encounters that caused the strongest changes in semi-major axis varied up to a fator 2. The indirect effect caused by the presence of other massive asteroids therefore introduces an additional source of uncertainty in estimating the long-term effect of close encounters with massive asteroids that was not accounted for in... (Complete abstract click electronic access below)

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Earth and Planetary Sciences, 1975 / Vita. / Bibliography: leaves 53-55. / by Norman Brenner. / Ph. D. / Ph. D. Massachusetts Institute of Technology, Department of Earth and Planetary Sciences

Orientador: Valerio Carruba / Banca: Ernesto Vieira Neto / Banca: Fernando Virgilio Roig / Resumo: Asteroides de alta inclinação são objetos com sin(i) > 0.3. Entre estes asteroides podemos distinguir objetos com inclinação menor que o centro da ressonância secular ν6 = g−g6 e objetos com inclinação superior. Os atuais mecanismos de mobilidade dinâmica não podem aumentar facilmente inclinações menores do que do centro da ressonância ν6. A presença de objetos de alta inclinação pode, portanto, estar relacionada com fases iniciais do Sistema Solar. Neste trabalho obtemos elementos próprios sintéticos para a região da família de Pallas, encontramos grupos dinâmicos e determinamos a significância estatística destes grupos. Estudamos a evolução dinâmica devida a perturbações planetárias e efeitos não gravitacionais das famílias e clumps identificados na região das famílias de Pallas e Hansa (Carruba 2010b). Estudamos regiões dinamicamente estáveis, que são surpreendentemente caracterizadas por um número muito baixo de asteroides, contrariamente a objetos de baixa inclinação que ocupam tudo a região dinamicamente viável. Identificamos duas areas caracterizadas por tempos de permanência de 100 milhões de anos o mais, quando a força Yarkovsky é considerada, com baixa densidade de asteroides. Obtemos elementos próprios sintéticos para 10865 objetos na região da família de Euphrosyne e identificamos famílias e clumps no domínio dos elementos próprios e frequências. Com relação a outros trabalhos sobre identificação de famílias na área, aqui nos investigamos o efeito que a rede local de ressonâncias seculares tem sobre a evolução dinâmica das famílias e clumps. Identificamos por primeira vez, novas populações de objetos em estados ressoantes de libração anti-alinhada de ν6 e anti-alinhada e alinhada de ν5. / Abstract: Highly inclined asteroids are objects with sin(i) > 0.3. Among these asteroids we can distinguish between objects with inclinations lower than the center of the secular resonance ν6 = g−g6 and objects with higher inclinations. The current mechanisms of dynamical mobility cannot easily increase inclinations to value higher than that of the center of the ν6 resonance. The presence of high inclination objects may therefore be related to early stages of the Solar System. In this work we obtained synthetic proper elements for the region of the Pallas family, we found dynamical groups and determined the statistical significance of these groups. We studied the dynamic the dynamical evolution caused by planetary perturbations and non-gravitational effects of the families and clumps identified in the region of the Pallas and Hansa families (Carruba 2010b). We studied regions dynamically stable that on surprisingly characterized by a low number of asteroids, contrary to objects of lower inclinations that tend to occupy all the viable stable regions. We identified two areas characterized by permanence time of 100 Myr or more when the Yarkovsky force is considered, but with a small number density of bodies. We obtained synthetic proper elements for 10865 objects in the region of the Euphrosyne families and identify families and clumps in the domain of proper elements and frequencies. With respect to other work on family identification in the area, here we investigated the role that the local web of secular resonances has had on the dynamical evolution of families and clumps. We identify for the first time, new populations of objects inν6 anti-aligned libration and ν5 anti-aligned and aligned resonant states. / Mestre

In this Dissertation we explore how the nature of tidal interactions tear gravitationally bound systems apart into distinct morphological and kinematic structures. We use the properties of these structures, persisting for billions of years, to investigate the potential of the Milky Way Galaxy and to disentangle the baryonic evolution of gas in dwarf galaxy interactions. We approach these problems through a combination of observations, and simulations, as well as comparisons between the two. In particular, we use the properties of the thin, curved stellar stream emerging from the old, Milky Way globular cluster, Palomar 5 (Pal 5) to show that its mere existence can rule out a moderately triaxial potential model of our Galaxy. Pal 5-like streams on appropriate orbits diffuse much further in space from the orbital path (dubbed “stream-fanning”) in this triaxial potential than in the oblate case. We further show that torques from the Milky Way’s Galactic bar, can create ever-widening gaps in stellar streams. The fact that the bar can create such under densities, demonstrates that we should be careful when interpreting gaps in stellar streams as indirect evidence of the existence of dark matter subhalos in our Galaxy. We carry out a systematic study of resolved neutral hydrogen (HI) synthesis maps of 10 interacting dwarf galaxy pairs. The pairs are located in a range of environments and captured at various interaction stages. We find that the neutral gas is extended in the interacting pairs when compared to non-paired analogs, indicating that gas is tidally pre- processed. Additionally, we find that dwarf-dwarf interactions enable the “parking” of gas at large distances to serve as a continual gas supply channel to the dwarfs until accretion by a more massive host. We model a specific dwarf pair in our sample, NGC 4490/85, which is an isolated analog of the Magellanic Clouds and is surrounded by a ∼50 kpc extended HI envelope. We use hybrid N-body and test-particle simulations along with a visualization interface to simultaneously reproduce the observed present-day morphology and kinematics. Our numerical results con- firm that encounters between two dwarf galaxies can “park” baryons at very large distances, without the aid of environmental effects. The extended tidal features will continue to evolve over several billion years which will affect the efficiency of gas stripping if such dwarf pairs are accreted by a massive host. In contrast, in isolated environments dwarf-dwarf interactions can create a long-lived supply mode of gas to the merger remnant potentially explaining the population of dwarfs in the field with large gas envelopes, but limited star formation. All of these topics share the common theme of utilizing morphological and kinematic structures left behind from ongoing gravitational interactions on various scales.

In this thesis we investigate several aspects of galaxy evolution. We begin by giving a brief introduction to the subject of galaxy evolution in the context of the Universe as we know it today. We discuss infrared surveys of galaxies as a tool for studying galaxy evolution. Initially, we are interested in the large scale environment of galaxies and identify clusters of galaxies at high redshift. We compare the mass and star-formation properties of galaxies in the cluster and field environments. To take this further we look to the AKARI all- sky survey and assess the potential of this survey for future studies. We calculate the completeness and reliability of the survey. Such wide surveys also allow for the possibility of studying rare and extreme phenomena. Such phenomena can push theories of galaxy evolution to their extremes and constrain these theories. We present the discovery of four such objects in the SWIRE survey. Finally, since environment plays a large role in the evolution of galaxies we extend this investigation to smaller scales. We investigate the progenitors of Type Ia Supernovae from a study of their host galaxies, which have implications for their use as standardisable candles.

Thèse de doctorat : Astronomie : Paris, Faculté des sciences : 1857. Thèse de doctorat : Géométrie : Paris, Faculté des sciences : 1857. / Titre provenant de l'écran-titre.

For centuries, an orderly view of planetary system architectures dominated the discourse on planetary systems. However, there is growing evidence that many planetary systems underwent a period of upheaval, during which giant planets "migrated" from where they formed. This thesis addresses a question key to understanding how planetary systems evolve: is planetary migration typically a smooth, disk-driven process or a violent process involving strong multi-body gravitational interactions? First, we analyze evidence from the dynamical structure of debris disks dynamically sculpted during planets' migration. Based on the orbital properties our own solar system's Kuiper belt, we deduce that Neptune likely underwent both planet-planet scattering and smooth migration caused by interactions with leftover planetesimals. In another planetary system, Beta Pictoris, we find that the giant planet discovered there must be responsible for the observed warp of the system's debris belt, reconciling observations that suggested otherwise. Second, we develop two new approaches for characterizing planetary orbits: one for distinguishing the signal of a planet's orbit from aliases, spurious signals caused by gaps in the time sampling of the data, and another to measure the eccentricity of a planet's orbit from transit photometry, "the photoeccentric effect." We use the photoeccentric effect to determine whether any of the giant planets discovered by the Kepler Mission are currently undergoing planetary migration on highly elliptical orbits. We find a lack of such "super-eccentric" Jupiters, allowing us to place an upper limit on the fraction of hot Jupiters created by the stellar binary Kozai mechanism. Finally, we find new correlations between the orbital properties of planets and the metallicity of their host stars. Planets orbiting metal-rich stars show signatures of strong planet-planet gravitational interactions, while those orbiting metal-poor stars do not. Taken together, the results of thesis suggest that suggest that both disk migration and planet-planet interactions likely play a role in setting the architectures of planetary systems. / Astronomy

In a multi-planet system, gravitational interactions cause orbital eccentricity variations. For non-resonant systems, classical secular theory reveals that the eccentricities are vector sums of contributions from several eigenmodes. Examination of the eigenvectors often reveals subsets of planets that interact especially strongly as dynamical groups. Perturbations from other sources, such as tides, are shared among the planets through the secular interactions. If one planet's eccentricity is tidally damped, all the eigenmodes damp so as to leave a signature on their amplitudes. Therefore, if one desires to include some a priori tidal damping in an orbital fit, solutions should not assume the current eccentricity of that planet to be low, but rather for the eigenmodes that damp quickly to have low amplitude. The tidally perturbed planet may retain a substantial eccentricity, because some eigenmodes will be longer-lived. The secular eigenmodes, including relative damping rates, have been calculated for all 72 non-resonant extra-solar systems with adequate data. Tides also affect evolution of planets' semi-major axes, which is coupled with eccentricity evolution. A planet that, alone, would be quickly circularized so as to not experience much semi-major axis migration, could rapidly be forced into the star in the presence of an outer planet. Also, though such an inner planet may now be gone, the eccentricity of the outer planet could have been damped due to tides that acted on the inner planet. Any inferences about the primordial orbits of observed planets must consider these effects. For systems where the inner planet has not yet reached the star, the planets' eccentricities can be constrained for any particular assumed tidal dissipation factor Q', e.g. for the KOI-543 system, if the inner planet is rocky, the eccentricities must be<0.001. The habitable zone around low-mass stars is close to the star, precisely where tides are important. Low-mass stars are very long lived, and can be very old currently. A habitable planet likely needs tectonics for cycles that regulate the atmosphere, but a planet's internal heat will decay over long timescales. However, an outer planet could maintain the inner planet's eccentricity, allowing tidal heating to maintain long-term habitability. Secular interactions, coupled with tidal effects, may be critical for planetary habitability.

A key challenge in low-thrust trajectory design is generating preliminary solutions that simultaneously detail the evolution of the spacecraft position and velocity vectors, as well as the thrust history. To address this difficulty, a dynamical model that incorporates a low-thrust force into the circular restricted 3-body problem (CR3BP), i.e., the CR3BP+LT, is constructed and analyzed. Control strategies that deliver specific energy changes (including zero energy change to deliver a conservative system) are derived and investigated, and dynamical structures within the CR3BP+LT are explored as candidate solutions to seed initial low-thrust trajectory designs. Furthermore, insights from dynamical systems theory are leveraged to inform the design process. In the combined model, the addition of a low-thrust force modifies the locations and stability of the equilibrium solutions, resulting in flow configurations that differ from the natural behavior in the CR3BP. The application of simplifying assumptions yields a conservative, autonomous system with properties that supply useful insights. For instance, "forbidden regions" at fixed energy levels bound low-thrust motion, and analytical equations are available to guide the navigation through energy space. Linearized dynamics about the equilibria supply hyperbolic and center manifold structures, similar to the ballistic CR3BP. Low-thrust periodic orbits in the vicinity of the equilibrium solutions also admit hyperbolic and center manifolds, providing an even greater number of dynamical structures to be employed in preliminary trajectory designs. Several applications of the structures and insights derived from the CR3BP+LT are presented, including several strategies for transit and capture near the smaller CR3BP primary body. Finally, an interactive trajectory design framework is presented to explore and utilize the structures and insights delivered by this investigation.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20898号 / 理博第4350号 / 新制||理||1624(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 田中 貴浩, 准教授 樽家 篤史, 教授 川合 光 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM