During the first billion years after the big bang, the large-scale cosmic web of structures we see today began to form. This was followed by the first stars and galaxies, which brought an end to the Dark Ages. These first luminous sources are thought to be the prime candidates which fuelled cosmic reionization, the last major phase transition of the Universe, from a neutral inter-galactic medium following recombination to the ionized state it remains in today. The physical processes which drive reionization encapsulate several areas of research, from cosmology and galaxy formation to radiative transfer and atomic physics. Even with the wealth of present-day observational information at our disposal, the processes are still not fully understood. Therefore we cannot model reionization analytically, instead turning to numerical simulations using observations to constrain our models. We perform a suite of fully-coupled radiation-hydrodynamical simulations of galaxy formation in cosmological volumes to probe the self-feedback of galaxies during the Epoch of Reionization. This research focuses on the transport of gas from the intergalactic medium onto dark matter halos, and consequences for semi-analytical models of galaxy formation. To improve on existing methods, which constrain the halo baryon fraction during reionization, we develop and train an artificial neural network to predict this quantity based on the physical properties of haloes. We demonstrate that this model is independent of redshift and reionization history, and can be trivially incorporated into semi-analytical models of galaxy formation. We further probe the physical processes which allow ionizing photons to escape from galaxies to reionize the Universe, specifically how stellar evolution uncertainties such as binary populations influence this process. Finally, we investigate to what extent a relative supersonic drift velocity between baryons and dark matter, present at recombination, may suppress the formation of the first objects and fundamentally alter their evolution. To do this, we develop a new method based on cosmological zoom simulations to include this effect in boxes much larger than the coherence length of the relative velocity for the first time.

Feedback -- from stars and supermassive black holes -- is the bottleneck of our understanding on galaxy formation: it is likely to be critical, but neither the working mechanism nor the impact is clear. Supernovae (SNe), the dominant feedback force associated with stars, is the subject of this thesis. We use high-resolution, 3D hydrodynamic simulations to study: (i) how a SN blast wave imparts energy to a multiphase ISM; (ii) how multiple SNe regulate a multiphase ISM; (iii) how SNe drive galactic outflows. We focus on better understanding the physics, quantifying the impacts, and testing the simulations against observations.

This thesis is concerned with the role the rich cluster environment plays in the evolution of its galaxy population. We approach this issue from two angles, first we use deep wide-field imaging to investigate the effect of the cluster environment on the spatial and luminosity distribution of galaxies. Secondly, we focus on one particularly interesting class of galaxy, the enigmatic E+A galaxies, using a combination of state-of-the-art telescopes and novel instrumentation to elucidate the physical mechanisms and environmental influences causing the rapid change in star-formation activity in these galaxies. We present results from a deep photometric study of the rich galaxy cluster Abell 2218 (z=0.18) based on Hubble Space Telescope images. These have been used to derive the cluster luminosity function to extremely faint limits. We find the faint-end slope of the luminosity function to vary with environment within the cluster - in the sense that the ratio of `dwarf' galaxies to `giant' galaxies increases in the lower-density outskirt regions. Using imaging obtained with the Isaac Newton Telescope (INT) we confirm the presence of luminosity segregation in Abell 2218. However, luminosity segregation in clusters does not appear to be ubiquitous, with two other clusters studied with the INT (A119 at z=0.04 and A2443 at z=0.11) showing no sign of luminosity segregation of their galaxy populations. We use integral field spectroscopy of a sample of E+A galaxies in intermediate redshift clusters, obtained with the FLAMES system on the European Southern Observatory's VLT and the GMOS instrument on Gemini-North, to determine the radial variation in the strength of Hdelta absorption in these galaxies, and hence map out the distribution of the recently formed stellar population. We find a diversity of behaviour amongst these galaxies in terms of the radial variation in Hdelta absorption: with gradients that are either negative, flat, or positive. By comparing with numerical simulations we suggest that the first of these different types of radial behaviour provides evidence for a merger/interaction origin, whereas the latter two types of behaviour are more consistent with the truncation of star formation in normal disk galaxies.

Si la formation des grandes structures de l'Univers est plutot bien comprise, celle des galaxies ainsi que leur évolution l'est beaucoup moins. On s'intéresse en particulier aux mécanismes de mise en route de la formation stellaire dans les galaxies. L'étude des galaxies lumineuses en infrarouge constitue une des approches pour répondre à ces questions. Le travail effectué au cours de cette thèse repose essentiellement sur l'analyse de données infrarouges provenant du satellite Spitzer.<br /><br />La première partie de ce travail porte sur l'étude de la<br />distribution spatiale des galaxies infrarouges. Nous avons introduit une nouvelle méthode pour mesurer la fonction de corrélation angulaire des galaxies. Cette méthode a été validée sur des simulations et des données. Nous avons également montré comment les effets de corrélation spatiale pouvaient biaiser les mesures de flux moyen réalisées par la méthode d'empilement. De plus, la<br />fonction de corrélation angulaire mesurée pour les sources sélectionnées à 3.6 microns et 24 microns montre un excès de corrélation aux petites échelles angulaires. Ceci pourrait être lié à l'interaction des galaxies à l'intérieur d'un meme halo de matière noire qui favoriserait alors les mécanismes d'émission infrarouge.<br /><br />Dans un second temps, nous nous sommes attachés à mieux caractériser le fond diffus infrarouge (CIB) en déterminant la contribution à ce fond des sources détectées à 3.6 microns et en la comparant à celle des sources sélectionnées à 24 microns. Nous avons également estimé la contribution au CIB à 3.6 et 24 microns des sources sélectionnées à 3.6 microns en fonction de leur taux de formation stellaire spécifique.<br /><br />Enfin, nous avons étudié les distributions spectrales d'énergie d'un grand nombre de galaxies situées entre z=0 et z=2 : nous avons montré d'une part que les luminosités à 8 et 24 microns étaient de bons traceurs de la luminosité totale infrarouge (et donc du taux de formation stellaire) et, d'autre part, que les propriétés de ces galaxies ne semblaient pas évoluer entre entre z=0 et z=1. Nous avons également étudié de façon détaillée le spectre infrarouge de 17 galaxies sélectionnées à 70 microns et nous avons montré que la luminosité relative des PAHs diminuait lorsque le champ de rayonnement<br />augmentait.

The abundance of satellite galaxies is a critical small-scale test of the standard cosmological model. From comparing the predictions of structure formation in simulations with observations of Local Group dwarf galaxies there is a clear mismatch in the abundance, leading to the so-called “missing satellites” problem. The comparison between simulation and observation have, however, suffered from a limited sample of satellite galaxies, with the only reasonably complete sample being from the most local galaxy groups. It is unknown whether the observed abundance of dwarf satellite galaxies of the nearest groups is statistically representative of the abundance of dwarf satellites in the greater universe. We construct a volume-limited sample of galaxies down to a well-defined stellar mass limit (M★ ≥ 6 × 109 Msun ) using the Atlas3D parent sample of spiral and ellipsoidal galaxies by Cappellari et al. 2011. In order to statistically identify bound satellites around galaxies in our primary catalogue, we apply cuts on the background based on the properties of known dwarf satellites of the Local Group using both the Sloan Digital Sky Survey Data Release 8 (SDSS DR8) (http://www.sdss3.org/dr8/) spectroscopic and photometric galaxy catalogues. We detect an over-density of faint objects at projected separations of < 500 kpc at S/N ∼ 8, corresponding to an average of 4.8 ± 0.65 satellite detections per primary after stacking these systems and subtracting the background. We further find that the over-density of faint objects strongly depends on primary morphology and magnitude. While the Milky Way seems to be unusual in its number of bright satellites, our faint end satellite abundances are in agreement from the ∆m luminosity function for primaries in our sample as bright as the Milky Way. Our work has extended the work of previous authors by several magnitudes further down the faint end of the luminosity function.

Proefschrift--Rijksuniversiteit Groningen, 2000. / Résumé en néerlandais. Notes bibliogr.

Thèse de doctorat : Astrophysique : Strasbourg 1 : 2007. / Titre provenant de l'écran-titre. Bibliogr. p. 199-200.

Thesis (Ph. D.)--University of Chicago, Department of Astronomy and Astrophysics, June 2001. / Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--Ohio State University, 2004. / Title from first page of PDF file. Document formatted into pages; contains xiv, 250 p.; also includes graphics (some col). Includes abstract and vita. Advisor: Terry Walker, Dept. of Physics. Includes bibliographical references (p. 227-250).

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