Galaxy evolution depends on a diverse suite of factors, from the environment in which the galaxy exists to the number of supernovae that explode throughout its history. The structure and stellar populations present will also be altered by a galaxy's merger history, stellar mass, star formation rate, among other influences. Some factors, like mergers, are dependent on the environment of the galaxy, while others, like feedback from star formation, are intrinsic to the galaxy themselves. Dwarf galaxies are sensitive to many of these factors due to their smaller masses, hence shallower potential wells. Dwarfs are also interesting in themselves as the least massive structures that can form stars, forming the faint limit of galaxy types. There is some indication that the evolutionary pathway of dwarfs might be different than their more massive counterparts. Indeed, some dwarfs may be the stripped remnants of larger galaxy after a major interaction. Regardless, dwarfs are thought to be the building blocks of larger galaxies via hierarchical galaxy formation and understanding these small dwarfs helps us build a more complete picture of galaxy formation and evolution at all masses. As dwarfs generally have low stellar mass, they are very faint. Our most complete sample of dwarfs is therefore restricted to those that are nearby. These nearby systems are dominated by dwarfs satellite to the Milky Way and M31. However, the evolution of these satellites will be greatly influenced by their massive host. By studying nearby isolated dwarfs, we can try to separate the secular evolutionary processes of dwarfs from the influence of their larger host. Additionally, stellar populations can be resolved in these nearby galaxies, and so their structures can be probed to much fainter regimes than integrated light studies allow. The Sagittarius Dwarf Irregular Galaxy (Sag DIG) is one of the most isolated, low mass galaxies, located at the edge of the Local Group. Its isolation from other galaxies coupled with its relative proximity provide an excellent opportunity to study the intrinsic properties of this low mass system. We preform an in-depth analysis of its resolved stellar populations and its structural properties as the first galaxy in the larger dataset, Solitary Local Dwarfs Survey (Solo). Solo is a wide field photometric study targeting every isolated dwarf galaxy within 3 Mpc of the Milky Way. Solo is based on (u)gi multi-band imaging from CFHT/MegaCam for northern targets, and Magellan/Megacam for southern targets. All galaxies fainter than M ~ -18 (in the V band) situated beyond the nominal virial radius of the Milky Way and M31 (> 300 kpc) are included in this volume-limited sample, for a total of 42 targets. For Sag DIG, we provide updated estimates of its central surface brightness and integrated luminosity, and trace its surface brightness profile to a level fainter than 30 mag./sq.arcsec. Sag DIG is well described by a highly elliptical (disk-like) system following a single component Sersic model. However, a low-level distortion is present at the outer edges of the galaxy that, were Sag DIG not so isolated, would likely be attributed to some kind of previous tidal interaction. Further, we find evidence of an extremely low level, extended distribution of stars beyond ~5 arcmins (> 1.5 kpc) that suggests Sag DIG may be embedded in a very low density stellar halo. We compare the stellar and HI structures of Sag DIG, and discuss results for this galaxy in relation to other isolated, dwarf irregular galaxies in the Local Group. Sag DIG, and the similarly isolated dwarf Aquarius, both have HI distributions that are more circular than their stellar components. In contrast, Wolf - Lundmark - Mellote (WLM), another isolated but slightly more massive dwarf, has stellar and HI components that trace each other well. Sag DIG and Aquarius also differ in that there is no signature of rotation in the HI of Sag DIG, while there is clear rotation in both the HI and stellar component for Aquarius. These preliminary comparisons demonstrate some of the potential analysis which will be possible on a much larger scale with the full Solo Survey. / Graduate / 0606 / higgs@uvic.ca

First, the baryonic content of simulated halos of virial masses between 5 x 10^{9} M_{\odot}$ to 5 x 10^{12} M_{\odot}$ in the APOSTLE project is examined in the context of the missing baryon problem. Baryonic particles in APOSTLE can be either stars or gas. Non-star-forming gas, or the circumgalactic medium (CGM) is further classified by temperature into the Cool CGM (CCGM, T < 10^{5} K), or the Warm-Hot CGM (WHCGM, T > 10^{5} K). APOSTLE halos are found to contain less than 60% of the expected mass of baryons (f_{b} = Ω{b}/Ω{m}, M_{b} = f_{b} x M_{200}) within their virial radius. The WHCGM contains 29% ± 10%, the CCGM 12% ± 5%, and the stars and star-forming gas 19% ± 5%. The metal content of the same halos is analyzed, and compared to the total metals produced by the stars within the virial radius. Over two thirds of the produced metals are retained within the halo, with 14% ± 3% in the WHCGM, 13% ± 4% in the CCGM, and 43% ± 9% in the stars and star-forming gas. Next, we focus on the overall distribution of matter within a 3Mpc radius from the Milky Way. Using the trends in APOSTLE volumes, I quantify both the ellipticity and orientation of this spatial distribution using the principal axes of the inertia tensor of the positions of these galaxies. The Zone of Avoidance has little impact on this result, and the short axis is aligned with that of the Supergalactic Plane, and is perpendicular to the vector separating the Milky Way and Andromeda galaxies. APOSTLE local group analogues are found to be similarly anisotropic, and like in the observed Local Group, the minor axis of that distribution is found to be perpendicular to the vector separating the two primaries. The angular momentum of the stellar disk shows weak alignment with the minor axis of the field galaxy distribution. In addition the simulations also suggest that the angular momenta of the two primary dark-matter halos tend to be anti-aligned. Additionally, stellar disks tend to orient themselves in the same direction as their halo. / Graduate

O objetivo desta tese é analisar aspectos do sistema de satélites da Via Láctea de relevância cosmológica. Dentre estes aspectos destacam-se dois: o censo de satélites da Galáxia – onde constata-se que a quantidade destes objetos é muito inferior ao predito por modelos cosmológicos do tipo Matéria Escura Fria – e a frequência anômala de satélites luminosos, como a Pequena e Grande Nuvem de Magalhães (SMC e LMC respectivamente). Além disso, a determinação dos parâmetros estruturais da LMC pode impor vínculos a sua formação, histórico orbital e sobre a massa de nossa Galáxia. Neste trabalho é desenvolvida uma técnica de busca por satélites da Via Láctea. Esta técnica foi otimizada para utilizar dados da nova geração de grandes surveys de maneira eficiente. Este código, o FindSat, foi validado em uma amostra de galáxias anãs conhecidas e se mostrou eficiente em detectar as galáxias anãs mais tênues de que se tem registro. A aplicação desse código a uma região do Sloan Digital Sky Survey (SDSS) ainda não explorada nesse sentido revelou uma série de candidatos a novos satélites. Foram selecionados os candidatos mais promissores para observação de follow-up. Estas observações revelaram que um destes candidatos é de fato um novo satélite da Via Láctea. Este novo objeto é muito provavelmente um aglomerado globular do halo em estágio avançado de dissolução, porém, seu tamanho e magnitude integrada colocamno em um domínio limítrofe entre aglomerado e galáxia anã. Através da cuidadosa análise dos demais candidatos, constatou-se que nenhum outro é de fato um novo satélite da Galáxia. Além disso, foi realizado o estudo do perfil de densidade e geometria da LMC. Este estudo utilizou dados de verificação científica do Dark Energy Survey (DES). Constatase que o perfil de densidades para estrelas jovens (< 3 Gyr) possui um raio de escala cerca de 50% menor que o da população velha (> 3 Gyr), favorecendo o cenário de formação tipo outside-in. O estudo da extensão da componente estelar da LMC revela um raio de maré de cerca de 18 kpc, permitindo o cálculo da massa dinâmica total da LMC. O valor de massa obtido favorece a hipótese onde as Nuvens de Magalhães estariam por sua primeira passagem pelo perigaláctico. Além disso, a distância heliocêntrica e espessura do disco da LMC foram determinadas utilizando estrelas do Red Clump (RC). Notou-se que regiões no extremo norte da LMC estão sistematicamente mais próximas de nós do que o esperado, este efeito evidencia o warp no disco dessa galáxia. Observou-se que a espessura do disco aumenta na periferia da LMC, caracterizando o fenômeno de flare. O aumento na espessura juntamente com a maior extensão da população velha da LMC é interpretado como a presença de dois componentes discoidais. Esta é a primeira evidência desse tipo baseada apenas em métodos de contagem de estrelas. / The goal of this thesis is to analyse comologically relevant aspects of the Milky Way (MW) satellite system. Among these we may highlight two: the census of MW satellites – where the observed number of these objects is much less than what is expected by Cold Dark Matter (CDM) models – and the anomalous frequency of luminous satellites, such as the Small and Large Magellanic Clouds (SMC and LMC respectively). Besides the cosmological importance of the Clouds, the determination of its structural parameters may help to constraint models for their formation, orbital history, and ultimately the mass assembly in our Galaxy. In this work a technique to search newMWsatellites is developed. This technique was optimized to run efficiently on large datasets, such as the ones being generated by the new generation of surveys. The code, FindSat was validated in a sample of well known MW satellites and has proven to be well succeeded even for the most faint of these objects. The application of this code to an unexplored region of the Sloan Digital Sky Survey (SDSS) revealed a large amount of new dwarf galaxy candidates, some of which where selected for follow-up observation. These observations led to the discovery of a new MW satellite. This new object is most likely a globular cluster in an extreme stage of dissolution. However, its integrated magnitude and size makes it difficult to discern it from a dwarf galaxy. By a careful analysis of the remaining candidates, it was shown that no other new satellite was in the sample. The density profile and geometry of the LMC was also analysed. This study used the recent science verification data from the Dark Energy Survey (DES). It was found that the density profile for young stars (< 3 Gyr) has a scale radius 50% smaller when compared to the one obtained for older stars (> 3 Gyr). This result favours the outsidein galaxy formation scenario. The total extension of the LMC stellar component was measured, allowing the estimate of a truncation radius of about 18 kpc. Assuming that this truncation has tidal origins the dynamical mass of the LMC is inferred. The mass value found favours the case for the first perigalactic passage of the Clouds. Besides that, the heliocentric distance and thickness of the LMC disk was determined using Red Clump (RC) stars. Evidence for warp was found in the North edge of the LMC, in the sense that the disk is systematically more distance than expected. While the thickness of the disk increases towards the outer parts of the LMC, which is a phenomena known as flare. This effect joined with the fact that the older LMC stellar population is more extended, favours the presence of two disk components in this galaxy. This is the first evidence of this kind based only on star counts.

Cette thèse de doctorat s’inscrit dans le domaine des finances publiques et des choix publics et s’articule autour des questions de polarisation idéologique, décentralisation et conflit. Elle est composée de trois chapitres qui peuvent être lus de façon indépendante. Dans le premier chapitre l’accent est mis sur l’importance de la polarisation idéologique entre mais aussi à l’intérieur des partis politiques sur le niveau et la composition des dépenses publiques cantonales. L’analyse est menée au niveau des parlements cantonaux suisses et repose sur l’exploitation et le traitement économétrique d’une base de données très riche.Nous avons fait deux contributions à la littérature sur l’impact de fragmentation politique sur les dépenses publiques.Premièrement, nous avons montré que la dispersion idéologique à l’intérieur des partis politiques est associée à des dépenses publiques plus élevées alors que la dispersion entre partis est associée avec moins de dépenses publiques. Cette constatation implique que le mode d’organisation et la discipline au sein des partis politiques ont de l’importance. Ce résultat est particulièrement intéressant car la littérature précédente a fait abstraction de la dispersion idéologique au sein des partis. Ensuite, nous avons montré que la dispersion idéologique est principalement pertinente pour les dépenses de fonctionnement. Le deuxième chapitre s’intéresse au conflit d’objectifs qui peut exister entre agents économiques dans le cadre d’un jeu en deux étapes avec paiements asymétriques. La littérature a montré que les défaillances de coordination sont fréquentes dans les jeux en une étape et que la communication peut aider les individus à se coordonner par l’emploi de stratégies de take turn pour réduire l’inégalité des gains à long terme. Notre contribution a été d’étudier si la communication a la même capacité dans un jeu en deux étapes où l’équilibre parfait en sous-jeux exige que les deux joueurs fassent des choix opposés aux deux étapes du jeu et acceptent des gains inégaux. Nos résultats montrent que les défaillances de coordination se produisent la moitié du temps et que 18% des paires utilisent la stratégie de take turn. La communication augmente considérablement la coordination sur l’équilibre parfait en sous-jeux car elle augmente la capacité des sujets à amorcer une stratégie de take turn et à la maintenir. Elle leur permet d’établir une stratégie de long terme qui accroît l’efficacité tout en diminuant les écarts de paiements, induits par les gains asymétriques, en échangeant leurs positions relatives d’une manière équitable. Nos résultats montrent que la communication peut résoudre les conflits de coordination, même dans des situations plus complexes que dans les jeux en une étape généralement étudiés jusqu’à présent. Le dernier chapitre s’intéresse à un type de conflit particulier : la sécession politique. Plus précisément il traite du lien entre sécession, décentralisation et identité de groupe. Nous essayons de déterminer, au moyen d’une expérience de laboratoire, si décentraliser l’offre de biens publics permet de réduire la probabilité de faire sécession. Nous mettons en exergue l’importance de l’identité au niveau local. Le protocole expérimental ne permet évidemment pas de reproduire l’ensemble des arbitrages auxquels les mouvements séparatistes font face dans le monde réel. Il permet, néanmoins, de capturer deux forces essentielles: la proximité avec le bien public qui réduit les phénomènes de passagers clandestins et rapproche le bien public des préférences du citoyens et l’importance des identités locales. Nos résultats indiquent que la décentralisation augmente les contributions aux biens locaux et diminue la probabilité de sécession aussi lorsque l’identité locale est rendue saillante. En fait, une forte identité locale augmente la probabilité de sécession seulement lorsque les membres des groupes locaux sont des coopérateurs et qu’ils contribuent aux bien publics locaux. / This PhD thesis falls within the fields of public finance and public choice. It studies the following issues: ideological polarization, decentralization and conflict. It consists of three chapters can be read independently. In the first chapter the focus is on the importance of ideological polarization between but also within political parties on the level and composition of cantonal public spending. The analysis is on Swiss cantonal parliaments and is based on the use and econometric treatment of a very rich database. We made two contributions to the literature on the impact of political fragmentation on public spending. First, we showed that ideological dispersion within political parties is associated with higher public spending while the dispersion between political parties is associated with less public spending. This finding implies that the mode of organization and discipline within political parties are both important. This result is particularly interesting given that previous literature has completely abstracted from ideological dispersion within political parties. Lastly, we showed that ideological dispersion between and within political parties is mainly relevant for current expenditures. The second chapter focuses on the conflict of objectives that may exist between economic agents in a two-stage game with asymmetric payoffs. The literature showed that coordination failures are frequent in one-stage games and that communication can help individuals coordinate with the use of take turn strategies that allow for a reduction in the payoffs’ inequality in the long run. Our contribution was to study whether communication has the same capacity in a two-stage game where the subgame perfect Nash equilibrium requires both players to make opposite choices at both stages of the game and accept unequal payoffs. Our results show that coordination failures occur half of the time and that 18% of the pairs use the take turn strategy. Communication significantly increases coordination on the subgame perfect Nash equi librium because it increases the ability of subjects to initiate a take turn strategy and to maintain it. Thus, communication allows subjects to establish a long-term strategy that increases efficiency and reduces payments differences, induced by the asymmetry in payoffs, by exchanging their relative positions in a fair way. Our results show that communication can solve coordination conflicts, even in more complex situations than in one-stage games usually studied until now. The last chapter focuses on a particular type of conflict: political secessions. Specifically, it addresses the link between secessions, decentralization and group identity. We aim at determining, by means of a laboratory experiment, if decentralizing the provision of public goods reduces the likelihood of secession. We emphasize the importance of local identity. Our experimental design, obviously, do not reproduce all the trade-offs that separatist movements face in the real world. It allows, however, capturing at least two key forces that drive these movements: the proximity to public goods that reduces the phenomena of free-riding and brings public goods closer to citizens’ preferences and the importance of local identities. Our results indicate that the Decentralization treatment increases contributions to local public goods and decreases the likelihood of secessions also when identity is made more salient. If fact, reinforcing local group identity increases the likelihood of secession only when local group members are cooperators.