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<p>Galaxies live in extended, non-luminous haloes of dark matter. How dark matter haloes are affected by environment has been examined using cosmological simulations, and resulting predictions tested for isolated and cluster galaxies. However, predictions have have yet to be tested in the intermediate density environment of galaxy groups. We present a weak galaxy-galaxy lensing analysis of galaxies in groups, with the aim of examining how the group environment affects the dark matter haloes of member galaxies. In particular, we address three questions: 1) whether the dark matter haloes of galaxies in groups are truncated relative to galaxies in the field, 2) how dark matter is distributed within the group environment and 3) whether the halo-to-stellar mass ratio is different between field and group galaxies. We use a basic stacking method and a maximum likelihood technique to parameterize the dark matter haloes of group and field galaxies. Our samples of intermediate redshift group and field galaxies were identified by the Group Environment and Evolution Collaboration in the CNOC2 Redshift Survey. For these data, we measure the average radial extent of a group galaxy dark matter halo to be $s_* = 54^{+114}_{-39}$ kpc, which hints at the possible truncation of galaxy haloes in the group environment. We develop a method of examining the distribution of dark matter within the galaxy group itself, but obtain inconclusive results. Our preliminary analysis of star formation efficiency (halo-to-stellar mass ratio) indicates group galaxies may be less efficient at forming stars compared to galaxies in the field. Larger data samples are required in order to conduct a more rigorous analysis.</p> / Master of Science (MSc)

<p>Protostellar discs are generally thought to drive molecular outflows and jets observed in star forming regions, but there has been some debate as to how they form. The details of the driving and collimation of outflows help determine how much mass is cleared out and how much energy is fed back into the surroundings. Recently it has been argued that the magnetic brake is so strong that early protostellar disks cannot form.</p> <p>We have performed 3D ideal magnetohydrodynamic (MHD) simulations of collapsing Bonnor–Ebert spheres, employing sink particles within an AMR grid and using a cooling function to model radiative cooling of the gas. This allows us to follow the formation and early evolution of the accretion disc (2−8)×10⁴ years further into the Class 0 phase of its evolution. We form a rotationally dominated disc with a radius of 100 AU embedded inside a transient, unstable, flattened, rotating structure extending out to 2000 AU. The inner disc becomes unstable to a warping instability due to the magnetic structure of the outflow, warping 30 deg with respect to the rotation–axis by the end of the simulation. The disc is unstable to a Parker instability and sheds magnetic loops, degrading the orientation of the mean threading field. This reduces and locally reverses the magnetic braking torque of the large scale field back upon the disc. The reduction of magnetic braking allows a nearly Keplerian disc to form and may be the key way in which low mass stellar systems produce rotationally dominated discs. We discuss the relevance of our disc misalignment concerning the formation of mis–aligned hot Jupiters.</p> <p>Protostellar outflows are implicated in clearing mass from collapsing cores, and limiting the final mass of newly formed stars. The details of the driving and collimation of outflows help determine how much mass is cleared out and how much energy is fed back into the surroundings. The simulations generate outflows which are precessing, kinked, contain internal shocks and extend to a scale of 0.1 pc end–to–end. Our disc–wind theory describes magneto–centrifugal driving throughout the outflow bubble. The bulk properties of the outflow agree well with observations. The outflow has two components, a larger low speed wind (v_r < 1.5 km/s) dominated by a toroidal magnetic field Bφ, and an inner centrifugally driven jet dominated by Bp with speeds up to 20 km/s. The ratio of mass flux from the disk surface com- pared to accretion in the disk is measured to be M_out/M_in ∼ 0.1 from the inner component, whereas in the outer component M_out/M_in ∼ 1.0. The jet is misaligned and precesses as the disc warps by 30 deg with respect to the z–axis. We measure star formation efficiencies of ε_core = 0.63 (and growing), higher than theoretical predictions of ε_core = 0.29−0.39 and observations ε_core = 0.33.</p> <p>These new results reported in this thesis, show that disks can form in strongly magnetized media, in agreement with the observations - and that outflows are not as efficient in clearing away collapsing gas as has been assumed in various theoretical models. Both of these results have important implications for disk formation, and the origin of the IMF, as described in this work.</p> / Doctor of Philosophy (PhD)

Yes / Infinium Human Methylation BeadChip is an array platform for complex evaluation of DNA methylation at an individual CpG locus in the human genome based on Illumina’s bead technology and is one of the most common techniques used in epigenome-wide association studies. Finding associations between epigenetic variation and phenotype is a significant challenge in biomedical research. The newest version, HumanMethylationEPIC, quantifies the DNA methylation level of 850,000 CpG sites, while the previous versions, HumanMethylation450 and HumanMethylation27, measured >450,000 and 27,000 loci, respectively. Although a number of bioinformatics tools have been developed to analyse this assay, they require some programming skills and experience in order to be usable. Results We have developed a pipeline for the Galaxy platform for those without experience aimed at DNA methylation analysis using the Infinium Human Methylation BeadChip. Our tool is integrated into Galaxy (http://galaxyproject.org), a web-based platform. This allows users to analyse data from the Infinium Human Methylation BeadChip in the easiest possible way. Conclusions The pipeline provides a group of integrated analytical methods wrapped into an easy-to-use interface. Our tool is available from the Galaxy ToolShed, GitHub repository, and also as a Docker image. The aim of this project is to make Infinium Human Methylation BeadChip analysis more flexible and accessible to everyone. / Research Development Fund Publication Prize Award winner, May 2020.

Dans le domaine complexe de l’archéologie galactique, l’étude des flux stellaires s’est imposée comme une voie essentielle pour dévoiler la formation et l’évolution des galaxies, en particulier celle de la Voie lactée. Ces systèmes stellaires perturbés portent l’empreinte de l’histoire de la Voie lactée, offrant des perspectives sur l’accrétion de galaxies plus petites et de grappes d’étoiles sur des milliards d’années. Avec l’avènement de la mission Gaia et de ses données d’observation inédites, l’application d’outils d’apprentissage automatique non supervisés à la détection d’anomalies est devenue de plus en plus pertinente dans la recherche de ces énigmatiques flux stellaires. L’objectif principal de cette recherche était d’exploiter la puissance des intégrales de mouvement et des algorithmes de regroupement pour élaborer une méthodologie permettant d’identifier les flux stellaires au sein du halo de la Voie lactée. Guidés par la volonté d’affiner notre compréhension des dynamiques complexes de la galaxie, nous nous sommes efforcés de développer une méthode robuste capable de mettre au jour ces structures stellaires perturbées. Notre approche a impliqué une évaluation exhaustive des algorithmes de regroupement, notamment Single Linkage, Ward, DBSCAN et OPTICS, afin de distinguer des groupes cohérents d’étoiles qui présentent des motifs ou des relations distincts, une caractéristique clé des flux stellaires. Les données synthétiques ont servi de terrain de test, facilitant l’évaluation des performances des algorithmes et l’étalonnage optimal des hyperparamètres. Cette exploration a couvert trois phases, englobant des flux isolés, la résilience face au bruit de fond et les complexités de dispersions de vitesse plus élevées. Alors que la méthodologie a donné des résultats favorables sur des données synthétiques, lorsque nous l’avons appliquée aux données de la Gaia Data Release 3 (DR3), nous avons constaté que les grappes étaient principalement situées autour du noyau galactique ou du Système solaire, contrairement à nos attentes de découvrir des courants stellaires dans le halo galactique. Cette divergence par rapport à nos résultats anticipés met en évidence la nature complexe de la dynamique de la Voie lactée et soulève un défi important couramment rencontré en apprentissage automatique : le problème hors distribution. La capacité des algorithmes d’apprentissage automatique à généraliser à partir des données d’entraînement vers de nouvelles données non vues peut être entravée par la présence de points de données qui tombent en dehors de la distribution sur laquelle ils ont été formés. Dans le contexte de notre recherche, ce défi souligne la nécessité de techniques avancées en détection d’anomalies et d’adapter les modèles d’apprentissage automatique pour gérer les complexités de l’observation du monde réel. / In the intricate realm of galactic archaeology, the study of stellar streams has emerged as a vital avenue for unraveling the formation and evolution of galaxies, particularly the Milky Way. These disrupted stellar systems, bear the imprint of the Milky Way’s history, offering insights into the accretion of smaller galaxies and star clusters over billions of years. With the advent of the Gaia mission and its unprecedented observational data, the application of unsupervised machine learning tools to anomaly detection has become increasingly relevant in the search for these elusive stellar streams. The primary aim of this research was to harness the power of integrals of motion and clustering algorithms to devise a methodology for identifying stellar streams within the halo of the Milky Way. Guided by the goal of refining our understanding of the galaxy’s intricate dynamics, we endeavored to develop a robust method capable of uncovering these disrupted stellar structures. Our approach involved a comprehensive evaluation of clustering algorithms, including Single Linkage, Ward, DBSCAN, and OPTICS, to distinguish cohesive groups of stars that exhibit distinct patterns or relationships—a key characteristic of stellar streams. Synthetic data served as a testing ground, facilitating algorithm performance assessment and optimal hyperparameter calibration. This exploration spanned three phases, encompassing isolated streams, resilience against background noise, and the complexities of higher velocity dispersions. While the methodology yielded favorable outcomes on synthetic data, when applied to the Gaia Data Release 3 (DR3) data, we found that clusters were predominantly located around the galactic core or the Solar System, in contrast to our expectations of discovering stellar streams in the galactic halo. This deviation from our anticipated results highlights the complex nature of the Milky Way’s dynamics and raises an important challenge commonly encountered in machine learning: the out-of-distribution problem. The ability of machine learning algorithms to generalize from training data to new, unseen data can be hindered by the presence of data points that fall outside the distribution they were trained on. In the context of our research, this challenge underscores the need for advanced techniques in anomaly detection and adapting machine learning models to handle real-world observational complexities.

Uppsatsen syftar till att undersöka om barn och ungdomslitteraturen tillägnat sig filosofiska tankegångar och hur detta har utryckts i fyra skönlitterära verk. Barnlitteraturen används i skolan framförallt för att öka läsförståelse och ordkunskap. I denna studie har jag pekat på att litteraturen även kan föra fram filosofiska idéer. Uppsatsen kan fungera som en vägvisare till hur filosofiska idéer kan hämtas från skönlitteraturen och på så sätt exemplifiera dessa med hjälp av litteraturen, men också hur vi på samma sätt kan göra litteraturen mer begriplig med hjälp av filosofiska exempel. Uppsatsen har visat att barnlitteraturen innehåller djupa och intressanta filosofiska tankegångar. Både äldre och nyare barnlitteratur kan därför med fördel användas i skolan för att introducera filosofiska begrepp på ett stimulerande sätt.

Dark matter is now accepted as an integral part of our universe, and galaxy dynamics have long provided the most convincing observational evidence for dark matter. Spiral galaxies have traditionally been used for these studies because of their more simple kinematics, however elliptical galaxies need to be understood as well. In this dissertation I present deep long-slit spectroscopy from the University of Texas’ Hobby-Eberly Telescope for a sample of elliptical galaxies. For a subsample of galaxies I fit axisymmetric orbit-superposition models with a range of dark halo density profiles. I find that all three galaxies modeled require a significant dark halo to explain their motions. However, the shape of the dark halo is not the expected NFW profile, but rather a profile with a flat central slope. I also discuss the galaxy masses, anisotropies, and stellar mass-to-light ratios. / text

La détermination de l'extrémité inférieure de la fonction de masse initiale (FMI) prévoit de fortes contraintes sur les théories de la formation des étoiles. IC4665 est un amas d'´étoile jeune (30Myr) et il a situe 356pc de la Terre. L'extinction est Av~ 0.59 ± 0.15 mag. WIRCam Y, J, H et K observations ont été faites par le CFHT et a comprise 10 champs (de 1.1sq.deg totale) et deux zones de contrle de 20'x20' chacun. Diagrammes couleur/magnitude et couleur/couleur ont été utilisées pour comparer les candidats sélectionnées par les modèles BT-SETTL 30 et 50Myr. Les images CH4off et CH4on ont été obtenus avec CFHT/WIRCam plus 0.11 sq.deg. dans IC348. Naines-T ont ensuite été identifiés à partir de leur couleur de 1.69μm d'absorption du méthane et trois candidats nain-T ont été trouvée avec CH4on−CH4 >0.4 mag. Extinction a été estimée à Av~ 5 − 12 mag. Les comparaisons avec les naines-T modèles, et des diagrammes couleur/couleur et magnitude, rejeter 2 entre 3 candidats en raison de leur extrême z′ − J coleur. L'objet reste n'est pas considéré comme un nain avant l'amas en raison d'un argument de densité en nombre ou l'extinction forte Av~ 12 mag, ni d'être un champ de fond nain-T qui serait devrait être beaucoup plus faible. Les modèles et les schémas de donner cet objet un type T6 préliminaires spectrale. Avec un peu de la masse de Jupiter, ce jeune candidat nain-T est potentiellement parmi les plus jeunes, des objets de masse plus faible détectée dans une région de formation d'´étoiles `a ce jour. Sa fréquence est conforme à l'extrapolation du courant lognormal FMI estime `a au domaine de masse planétaire.

Mergers are known to be essential in the formation of large scale structures and to have a significant role in the history of galaxy formation and evolution. Besides a morphological transformation, mergers induce important bursts of star formation. These starburst are characterised by high Star Formation Efficiencies (SFEs) and Specific Star Formation Rates, i.e., high Star Formation Rates (SFR) per unit of gas mass and high SFR per unit of stellar mass, respectively, compared to spiral galaxies. At all redshifts, starburst galaxies are outliers of the sequence of star-forming galaxies defined by spiral galaxies. We have investigated the origin of the starburst-mode of star formation, in three local interacting systems: Arp 245, Arp 105 and NGC7252. We combined high-resolution JVLA observations of the 21-cm line, tracing the Hi diffuse gas, with UV GALEX observations, tracing the young star-forming regions. We probe the local physical conditions of the Inter- Stellar Medium (ISM) for independent star-forming regions and explore the atomic-to-dense gas transformation in different environments. The SFR/H i ratio is found to be much higher in central regions, compared to outer regions, showing a higher dense gas fraction (or lower Hi gas fraction) in these regions. In the outer regions of the systems, i.e., the tidal tails, where the gas phase is mostly atomic, we find SFR/H i ratios higher than in standard Hi-dominated environments, i.e., outer discs of spiral galaxies and dwarf galaxies. Thus, our analysis reveals that the outer regions of mergers are characterised by high SFEs, compared to the standard mode of star formation. The observation of high dense gas fractions in interacting systems is consistent with the predictions of numerical simulations; it results from the increase of the gas turbulence during a merger. The merger is likely to affect the star-forming properties of the system at all spatial scales, from large scales, with a globally enhanced turbulence, to small scales, with possible modifications of the initial mass function. From a high-resolution numerical simulation of the major merger of two spiral galaxies, we analyse the effects of the galaxy interaction on the star forming properties of the ISM at the scale of star clusters. The increase of the gas turbulence is likely able to explain the formation of Super Star Clusters in the system. Our investigation of the SFR–H i relation in galaxy mergers will be complemented by highresolution Hi data for additional systems, and pushed to yet smaller spatial scales.

La philosophie de cette thèse est de dire que nos plus grandes chances de trouver et de caractériser les ingrédients essentiels du modèle cosmologique passe par l'élargissement de l'éventail des méthodes que l'on peut utiliser dans le but de trouver une nouvelle physique. Bien qu'il soit d'une importance primordiale de continuer à affiner, à de-biaiser et à rendre plus puissantes, les stratégies qui ont contribué à établir le modèle de concordance, il est également crucial de remettre en question, avec de nouvelles méthodes, tous les secteurs de l'actuel paradigme cosmologique. Cette thèse, par conséquent, s'engage dans le défi de développer des sondes cosmologiques nouvelle et performantes qui visent à optimiser les résultats scientifiques des futures grand sondages de galaxies. L'objectif est double. Du côté théorique, je cherche à mettre au point de nouvelles stratégies de test qui sont peu (voire pas du tout) affectées par des incertitudes astrophysiques ou par des modèles phénoménologiques qui ne sont pas complet . Cela rendra les interprétations cosmologiques plus facile et plus sûr. Du côté des observations, l'objectif est d'évaluer les performances des stratégies proposées en utilisant les données actuelles, dans le but de démontrer leur potentiel pour les futures grandes missions cosmologiques tels que BigBoss et EUCLID. / The philosophy of this thesis is that our best chances of finding and characterizing the essential ingredients of a well grounded cosmological model is by enlarging the arsenal of methods with which we can hunt for new physics. While it is of paramount importance to continue to refine, de-bias and power, the very same testing strategies that contributed to establish the concordance model, it is also crucial to challenge, with new methods, all the sectors of the current cosmological paradigm. This thesis, therefore, engages in the challenge of developing new and performant cosmic probes that aim at optimizing the scientific output of future large redshift surveys. The goal is twofold. From the theoretical side, I aim at developing new testing strategies that are minimally (if not at all) affected by astrophysical uncertainties or by not fully motivated phenomenological models. This will make cosmological interpretations easier and safer. From the observational side, the goal is to gauge the performances of the proposed strategies using current, state of the art, redshift data, and to demonstrate their potential for the future large cosmological missions such as BigBOSS and EUCLID.