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Galaxies with large amounts of dust, bright at submillimeter wavelengths, and explosive star formation in the early universe are called "submillimeter-wave galaxies. What is the importance of observing these galaxies? First of all, the rate of star formation, which is not observable in visible or infrared light, increases rapidly as we move back in time. In other words, to obtain a complete picture of star formation activity in the universe, it is essential to search for star-forming galaxies in the early universe and study their number and brightness to determine how they have changed over the course of history.Analysis of the ADFS(AKARI Deep Field South) data detected several spectra that could be considered CO emission lines.

The reservoir of molecular gas (H$_{\rm 2}$) represents the fuel for the star formation (SF) of a galaxy. Connecting the star formation rate (SFR) to the available H$_{\rm 2}$ is key to accurately model SF in cosmological simulations of galaxy formation. We investigate how modifying the underlying modelling of H$_{\rm 2}$ and the description of stellar feedback in low-metallicity environments (LMF, i.e. low-metallicity stellar feedback) in cosmological, zoomed-in simulations of a Milky Way-size halo influences the formation history of the forming, spiral galaxy and its final properties. We exploit two different models to compute the molecular fraction of cold gas (f$_{\rm H_{\rm 2}}$): $i)$ the theoretical model by Krumholz et al. (2009b) and $ii)$ the phenomenological prescription by Blitz & Rosolowsky (2006). We find that the model adopted to estimate f$_{\rm H_{\rm 2}}$ plays a key role in determining final properties and in shaping the morphology of the galaxy. The clumpier interstellar medium (ISM) and the more complex H$_{\rm 2}$ distribution that the Krumholz et al. (2009b) model predicts result in better agreement with observations of nearby disc galaxies. This shows how crucial it is to link the SFR to the physical properties of the star-forming, molecular ISM. The additional source of energy that LMF supplies in a metal-poor ISM is key in controlling SF at high redshift and in regulating the reservoir of SF across cosmic time. Not only is LMF able to regulate cooling properties of the ISM, but it also reduces the stellar mass of the galaxy bulge. These findings can foster the improvement of the numerical modelling of SF in cosmological simulations., accepted for publication in MNRAS

The development and implementation of GEAR-RT, a radiative transfer solver using the M1 closure in the open source code SWIFT, is presented, and validated using standard tests for radiative transfer. GEAR-RT is modeled after RAMSES-RT (Rosdahl et al. 2013) with some key differences. Firstly, while RAMSES-RT uses Finite Volume methods and an Adaptive Mesh Refinement (AMR) strategy, GEAR-RT employs particles as discretization elements and solves the equations using a Finite Volume Particle Method (FVPM). Secondly, GEAR-RT makes use of the task-based parallelization strategy of SWIFT, which allows for optimized load balancing, increased cache efficiency, asynchronous communications, and a domain decomposition based on work rather than on data. GEAR-RT is able to perform sub-cycles of radiative transfer steps w.r.t. a single hydrodynamics step. Radiation requires much smaller time step sizes than hydrodynamics, and sub-cycling permits calculations which are not strictly necessary to be skipped. Indeed, in a test case with gravity, hydrodynamics, and radiative transfer, the sub-cycling is able to reduce the runtime of a simulation by over 90%. Allowing only a part of the involved physics to be sub-cycled is a contrived matter when task-based parallelism is involved, and is an entirely novel feature in SWIFT. Since GEAR-RT uses a FVPM, a detailed introduction into Finite Volume methods and Finite Volume Particle Methods is presented. In astrophysical literature, two FVPM methods are written about: Hopkins (2015) have implemented one in their GIZMO code, while the one mentioned in Ivanova et al. (2013) isn't used to date. In this work, I test an implementation of the Ivanova et al. (2013) version, and conclude that in its current form, it is not suitable for use with particles which are co-moving with the fluid, which in turn is an essential feature for cosmological simulations., Comment: PhD Thesis

We compare stellar mass surface density, metallicity, age, and line-of-sight velocity dispersion profiles in massive ($M_*\geq10^{10.5}\,\mathrm{M_\odot}$) present-day early-type galaxies (ETGs) from the MaNGA survey with simulated galaxies from the TNG100 simulation of the IllustrisTNG suite. We find an excellent agreement between the stellar mass surface density profiles of MaNGA and TNG100 ETGs, both in shape and normalisation. Moreover, TNG100 reproduces the shapes of the profiles of stellar metallicity and age, as well as the normalisation of velocity dispersion distributions of MaNGA ETGs. We generally also find good agreement when comparing the stellar profiles of central and satellite galaxies between MaNGA and TNG100. An exception is the velocity dispersion profiles of very massive ($M_*\gtrsim10^{11.5}\,\mathrm{M_\odot}$) central galaxies, which, on average, are significantly higher in TNG100 than in MaNGA ($\approx50\,\mathrm{km\,s^{-1}}$). We study the radial profiles of $\mathit{in}$-$\mathit{situ}$ and $\mathit{ex}$-$\mathit{situ}$ stars in TNG100 and discuss the extent to which each population contributes to the observed MaNGA profiles. Our analysis lends significant support to the idea that high-mass ($M_*\gtrsim10^{11}\,\mathrm{M_\odot}$) ETGs in the present-day Universe are the result of a merger-driven evolution marked by major mergers that tend to homogenise the stellar populations of the progenitors in the merger remnant., 22 pages, 9 figures, accepted for publication in MNRAS

Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UAM, We introduce gizmo-simba, a new suite of galaxy cluster simulations within The Three Hundred project. The Three Hundred consists of zoom re-simulations of 324 clusters with M 200 ≳ 1014.8, M ⊙ drawn from the MultiDark-Planck N-body simulation, run using several hydrodynamic and semi-analytical codes. The gizmo-simba suite adds a state-of-the-art galaxy formation model based on the highly successful Simba simulation, mildly re-calibrated to match z = 0 cluster stellar properties. Comparing to The Three Hundred zooms run with gadget-x, we find intrinsic differences in the evolution of the stellar and gas mass fractions, BCG ages, and galaxy colour-magnitude diagrams, with gizmo-simba generally providing a good match to available data at z ≈ 0. gizmo-simba's unique black hole growth and feedback model yields agreement with the observed BH scaling relations at the intermediate-mass range and predicts a slightly different slope at high masses where few observations currently lie. Gizmo-Simba provides a new and novel platform to elucidate the co-evolution of galaxies, gas, and black holes within the densest cosmic environments

Undisturbed galaxy clusters are characterized by a massive and large elliptical galaxy at their center, i.e. the Brightest Cluster Galaxy (BCG). How these central galaxies form is still debated. According to most models, a typical epoch for their assembly is z~1-2. We have performed a detailed multi-wavelength analysis of the core of XDCPJ0044.0-2033 (XDCP0044), one of the most massive and densest galaxy clusters currently known at redshift z~1.6, whose central galaxy population shows high star formation compared to lower-z clusters and an X-ray AGN located close to its center. SINFONI J-, H- and KMOS YJ-, H- bands spectroscopic data have been analyzed, together with deep archival HST photometric data in F105W, F140W, and F160W bands, Chandra X-ray, radio JVLA data at 1-2 GHz, and ALMA band-6 observations. In the central region of the cluster (~70x70 kpc^2), 2 systems of interacting galaxies have been identified and studied (Complex A and B), with a total of 7 confirmed cluster members. These galaxies show perturbed morphologies and 3 of them show signs of AGN activity. In particular, 2 type-1 AGN with typical broad lines have been found at the center of each complex (both of them X-ray obscured and highly accreting; Eddington ratio ~0.5), while a type-2 AGN has been discovered in Complex A. The AGN at the center of Complex B is also detected in X-ray while the other 2 are spatially related to radio emission. The 3 AGN provide one of the closest AGN triple at z>1 revealed so far with a minimum(maximum) projected distance of ~10(40) kpc. The observation of high star formation, merger signatures and nuclear activity in the core of XDCP0044 suggests that all these processes are key ingredients in shaping the nascent BCG. According to our data, XDCP0044 could form a typical massive galaxy of 10^12 Msun, hosting a Black Hole of 2x10^8-10^9 Msun, in a time scale of the order of ~2.5 Gyrs., 15 pages, 10 figures, 5 tables. Accepted to MNRAS in 2020 August 14

We complete the formulation of the standard model of first star formation by exploring the possible impact of LiH cooling, which has been neglected in previous simulations of non-linear collapse. Specifically, we find that at redshift z [greater than or equivalent to] 5, the cooling by LiH has no effect on the thermal evolution of shocked primordial gas, and of collapsing primordial gas into minihalos or relic H II regions, even if the primordial lithium abundance were enhanced by one order of magnitude. Adding the most important lithium species to a minimum network of primordial chemistry, we demonstrate that insufficient LiH is produced in all cases considered, about (LiH/Li) [approximately equal] 10⁻⁹ for T [less than or equivalent to] 100 K. Indeed, LiH cooling would only be marginally significant in shocked primordial gas for the highly unlikely case that the LiH abundance were increased by nine orders of magnitude, implying that all lithium would have to be converted into LiH. In this study, photo-destruction processes are not considered, and the collisional disassociation rate of LiH is possibly underestimated, rendering our results an extreme upper limit. Therefore, the cooling by LiH can safely be neglected for the thermal evolution of Population III star-forming gas.

This thesis aims to enhance our understanding of galaxies by testing theoretical models of galaxy formation against observations, particularly in the cases of extreme systems which have been found to have an excess of baryonic mass in their central regions, in the form of either supermassive black holes or stellar populations, thus harbouring "monsters" in the deep. To this end we use the EAGLE project, a suite of cosmological, hydrodynamical simulations of galaxy formation and evolution that have been calibrated to reproduce the number density and sizes of galaxies in the Universe. We find that galaxies with supermassive black holes that are much more massive than expected given their stellar mass are predicted to exist and they become overmassive through early formation and/or tidal stripping from more massive galaxies. Recent evidence for excess stellar mass in the centres of high-mass, early-type galaxies has fueled claims that the stellar initial mass function (IMF) may be variable. We test the consequences of such variations in the EAGLE model by performing two additional simulations in which the IMF becomes respectively top-heavy or bottom-heavy in high-pressure environments. The strong effects of such variations are explored in terms of scaling relations between, and within, galaxies.

This thesis investigates how galaxies form and what diversifies the evolutionary histories of galaxies. The first part of this thesis describes the identification of luminous galaxies in the early Universe and the follow-up study of their properties with the Very Large Telescope, ALMA and the Hubble Space Telescope. Luminous galaxies are assembling through merging of multiple components and heavy elements as carbon are already in place relatively shortly after galaxies have formed. The second part describes the study of the Lyman-alpha escape fraction of galaxies at the peak of star formation history. The Lyman-alpha escape fraction is generally low, except for rare massive galaxies with AGN activity or for low mass galaxies. This implies that Lyman-alpha radiation escapes more efficiently in the early Universe, when galaxies tend to be less massive with a lower dust content. The final part of this thesis is a theoretical investigation of the co-evolution of dark matter halos and galaxies in the cosmological hydrodynamical EAGLE simulation. Galaxy stellar mass growth is driven by both the mass and formation time of dark matter halos. As a result, present-day growth rates of galaxies are coherent with the long time-scale histories.

This thesis investigates the structural evolution and assembly of galaxies since the first few billions years after the big bang. It makes use of the CANDELs and UVISTA galaxy surveys, the EAGLE hydrodynamical simulation as well as spectroscopy from XShooter on the VLT. Within this thesis I attempt to answer when stellar mass was assembled onto galaxies, where those stars were deposited as well as the physical mechanisms which underly that assembly.

Recovering the origins of lenticular galaxies can shed light on the understanding of galaxy formation and evolution, since they present properties that can be found in both elliptical and spiral galaxies. In this work we study the kinematics of the globular cluster (GC) systems of three lenticular galaxies located in low density environments (NGC 2768, NGC 3115 and NGC 7457), and compare them with the kinematics of planetary nebulae (PNe). The PNe and GC data come from the Planetary Nebulae Spectrograph and the SLUGGS Surveys. Through photometric spheroid-disc decomposition and PNe kinematics we find the probability for a given GC to belong to either the spheroid or the disc of its host galaxy or be rejected from the model. We find that there is no correlation between the components that the GCs are likely to belong to and their colours. Particularly, for NGC 2768 we find that its red GCs display rotation preferentially at inner radii (Re, 13 pages, 10 figures, Accepted for publication in MNRAS

We present a study on the stellar age and metallicity distributions for 1105 galaxies using the STARLIGHT software on MaNGA integral field spectra. We derive age and metallicity gradients by fitting straight lines to the radial profiles, and explore their correlations with total stellar mass M*, NUV-r colour and environments, as identified by both the large scale structure (LSS) type and the local density. We find that the mean age and metallicity gradients are close to zero but slightly negative, which is consistent with the inside-out formation scenario. Within our sample, we find that both the age and metallicity gradients show weak or no correlation with either the LSS type or local density environment. In addition, we also study the environmental dependence of age and metallicity values at the effective radii. The age and metallicity values are highly correlated with M* and NUV-r and are also dependent on LSS type as well as local density. Low-mass galaxies tend to be younger and have lower metallicity in low-density environments while high-mass galaxies are less affected by environment., 18 pages, 24 figures, accepted for publication in MNRAS

We study the galaxy populations in 74 Sunyaev–Zeldovich effect selected clusters from the South Pole Telescope survey, which have been imaged in the science verification phase of the Dark Energy Survey. The sample extends up to z ∼ 1.1 with 4 × 1014M ≤ M200 ≤ 3 × 1015M . Using the band containing the 4000 Å break and its redward neighbour, we study the colour–magnitude distributions of cluster galaxies to ∼m∗ + 2, finding that: (1)The intrinsic rest frame g − r colour width of the red sequence (RS) population is ∼0.03 out to z ∼ 0.85 with a preference for an increase to ∼0.07 at z = 1, and (2) the prominence of the RS declines beyond z ∼ 0.6. The spatial distribution of cluster galaxies is well described by the NFW profile out to 4R200 with a concentration of cg = 3.59+0.20 −0.18, 5.37+0.27 −0.24 and 1.38+0.21 −0.19 for the full, the RS and the blue non-RS populations, respectively, but with ∼40 per cent to 55 per cent cluster to cluster variation and no statistically significant redshift or mass trends. The number of galaxies within the virial region N200 exhibits a mass trend indicating that the number of galaxies per unit total mass is lower in the most massive clusters, and shows no significant redshift trend. The RS fraction within R200 is (68 ± 3) per cent at z = 0.46, varies from ∼55 per cent at z = 1 to ∼80 per cent at z = 0.1 and exhibits intrinsic variation among clusters of ∼14 per cent. We discuss a model that suggests that the observed redshift trend in RS fraction favours a transformation time-scale for infalling field galaxies to become RS galaxies of 2–3 Gyr.

Interactions between galaxies and their larger scale environment is a central tenet of structure formation theory. However, this idea encompasses a long list of processes. Indeed, galaxies grow from intense gas inflows at high-redshift and acquire spin through tidal torques on larger scales while merging with one another at the same time. None of these processes is independent from the large scale distribution of matter, strikingly anisotropic and consisting of an extended network of voids delimited by sheets, themselves segmented by high-density filaments within which matter flows towards compact nodes where they intersect. Such a structure imprints its geometry on cosmic flows, especially gas inflows and drifting galaxies, ultimately shaping the distribution of galactic properties.This work investigates some of these correlations between galactic and extra-galactic scales in the hydrodynamical cosmological simulation Horizon-AGN. First, I analyze and quantify the spin orientations of galaxies and show that both minor and major mergers can drive important spin swings. I further investigate the distribution of satellite galaxies around a more massive host and find it to be also fairly correlated to the direction of the surrounding filament. However, this trend is in competition with a tendency for satellites to align their orbits in the central galactic plane especially in the inner parts of the halo.Finally, I study the impact of mergers and diffuse accretion on the size and shape of galaxies at the peak of cosmic star formation history. The main results statistically support the gas-poor minor merger scenario to interpret the loss of compacity of spheroids at low-z., Les interactions entre les galaxies et leur environnement à grande échelle constituent une pierre angulaire de la théorie de formation des structures. Cependant, derrière cette idée se cache une longue liste de processus. En effet, les galaxies grandissent au sein d'intenses courants de gaz à haut redshift et acquièrent du moment angulaire grâce aux couples de marée exercés par les grandes échelles, tout en fusionnant avec d'autres galaxies. Aucun de ces mécanismes n'est indépendant de la distribution de matière à grande échelle, fortement anisotrope, constituée d'un réseau de vides délimités par des murs, eux-mêmes segmentés par des filaments de haute densité dans lesquels la matière s'écoule en direction des noeuds compacts. La géométrie d'une telle structure influe fortement sur les écoulements cosmiques, notamment les flux de gaz et de galaxies en migration vers les noeuds. Cela modifie en conséquence la distribution et les propriétés des galaxies. Cette thèse explore certaines de ces corrélations entre les échelles galactiques et extra-galactiques dans la simulation cosmologique hydrodynamique HorizonAGN. Tout d'abord, j'analyse et quantifie l'orientation du moment angulaire des galaxies puis montre que les fusions majeures comme mineures peuvent provoquer d'importantes bascules de ce dernier. J'étudie par la suite la distribution des galaxies satellites autour de leur hôte plus massive et mets à jour des corrélations avec la direction du filament voisin ainsi qu'avec le plan de leur galaxie centrale. Enfin, j'étudie l'impact des fusions galactiques et de l'accrétion diffuse sur la taille et sur la forme des galaxies lors du pic cosmique de formation stellaire.

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved, From mock Hubble Space Telescope images, we quantify non-parametric statistics of galaxy morphology, thereby predicting the emergence of relationships among stellar mass, star formation, and observed rest-frame optical structure at 1 < z < 3. We measure automated diagnostics of galaxy morphology in cosmological simulations of the formation of 22 central galaxies with 9.3 < log10 M_*/M_sun < 10.7. These high-spatial-resolution zoom-in calculations enable accurate modeling of the rest-frame UV and optical morphology. Even with small numbers of galaxies, we find that structural evolution is neither universal nor monotonic: galaxy interactions can trigger either bulge or disc formation, and optically bulge-dominated galaxies at this mass may not remain so forever. Simulated galaxies with M_* > 10^10 M_sun contain relatively more disc-dominated light profiles than those with lower mass, reflecting significant disc brightening in some haloes at 1 < z < 2. By this epoch, simulated galaxies with specific star formation rates below 10^-9.7 yr^-1 are more likely than normal star-formers to have a broader mix of structural types, especially at M_* > 10^10 M_sun. We analyze a cosmological major merger at z ~ 1.5 and find that the newly proposed MID morphology diagnostics trace later merger stages while G-M20 trace earlier ones. MID is sensitive also to clumpy star-forming discs. The observability time of typical MID-enhanced events in our simulation sample is less than 100 Myr. A larger sample of cosmological assembly histories may be required to calibrate such diagnostics in the face of their sensitivity to viewing angle, segmentation algorithm, and various phenomena such as clumpy star formation and minor mergers, This work was partially supported by MINECO-AYA2012-31101. DC is a Juan de la Cierva fellow. This research has been partly supported by ISF grant 24/12, by NSF grant AST-1010033, and by the I-CORE Program of the PBC and the ISF grant 1829/12. GS and JL appreciate support from the HST grants program, number HST-AR-12856:01-A. Support for program #12856 (PI J. Lotz) was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society©: 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved, We study the accretion along streams from the cosmic web into high-redshift massive galaxies using three sets of AMR hydrocosmological simulations. We find that the streams keep a roughly constant accretion rate as they penetrate into the halo centre. The mean accretion rate follows the mass and redshift dependence predicted for haloes by the EPS approximation, ˙M ∝ M1.25 vir (1 + z)2.5. The distribution of the accretion rates can well be described by a sum of two Gaussians, the primary corresponding to ‘smooth inflow’ and the secondary to ‘mergers’. The same functional form was already found for the distributions of specific star formation rates in observations. The mass fraction in the smooth component is 60–90 per cent, insensitive to redshift or halo mass. The simulations with strong feedback show clear signs of reaccretion due to recycling of galactic winds. The mean accretion rate for the mergers is a factor 2–3 larger than that of the smooth component. The standard deviation of the merger accretion rate is 0.2–0.3 dex, showing no trend with mass or redshift. For the smooth component it is 0.12–0.24 dex, This work was supported by FWF project number M 1590-N27 and by MINECO project number AYA 2012-32295.

We present a new technique for modelling submillimetre galaxies (SMGs): the 'Count Matching' approach. Using light cones drawn from a semi-analytic model of galaxy formation, we choose physical galaxy properties given by the model as proxies for their submillimetre luminosities, assuming a monotonic relationship. As recent interferometric observations of the Extended Chandra Deep Field-South show that the brightest sources detected by single-dish telescopes are comprised by emission from multiple fainter sources, we assign the submillimetre fluxes so that the combined Large APEX BOlometer CAmera (LABOCA) plus bright-end Atacama Large Millimeter/submillimeter Array observed number counts for this field are reproduced. After turning the model catalogues given by the proxies into submillimetre maps, we perform a source extraction to include the effects of the observational process on the recovered counts and galaxy properties. We find that for all proxies, there are lines of sight giving counts consistent with those derived from LABOCA observations, even for input sources with randomized positions in the simulated map. Comparing the recovered redshift, stellar mass and host halo mass distributions for model SMGs with observational data, we find that the best among the proposed proxies is that in which the submillimetre luminosity increases monotonically with the product between dust mass and star formation rate (SFR). This proxy naturally reproduces a positive trend between SFR and bolometric IR luminosity. The majority of components of blended sources are spatially unassociated., Instituto de Astrofísica de La Plata

We observed the Hubble Deep Field South with the new panoramic integral field spectrograph MUSE that we built and just commissioned at the VLT. The data cube resulting from 27 hours of integration covers one arcmin^2 field of view at an unprecedented depth with a 1 sigma emission line surface brightness limit of 1x$10^{-19}$ erg/s/cm$^2$/arcsec$^2$ and contains ~90,000 spectra. We present the combined and calibrated data cube, and we perform a first-pass analysis of the sources detected in the HDF-S imaging. We measured the redshifts of 189 sources up to a magnitude F814W = 29.5, increasing by more than an order of magnitude the number of known spectroscopic redshifts in this field. We also discovered 26 Lya emitting galaxies which are not detected in the HST WFPC2 deep broad band images. The intermediate spectral resolution of 2.3{\AA} allows us to separate resolved asymmetric Lya emitters, [O II] emitters, and C III] emitters and the large instantaneous wavelength range of 4500{\AA} helps to identify single emission lines. We also show how the three dimensional information of MUSE helps to resolve sources which are confused at ground-based image quality. Overall, secure identifications are provided for 83% of the 227 emission line sources detected in the MUSE data cube and for 32% of the 586 sources identified in the HST catalog of Casertano et al 2000. The overall redshift distribution is fairly flat to z=6.3, with a reduction between z=1.5 to 2.9, in the well-known redshift desert. The field of view of MUSE also allowed us to detect 17 groups within the field. We checked that the number counts of [O II] and Ly-a emitters are roughly consistent with predictions from the literature. Using two examples we demonstrate that MUSE is able to provide exquisite spatially resolved spectroscopic information on intermediate redshift galaxies present in the field., Comment: 21 pages, 20 figures. Note that the catalogues, data cube and associated spectra will be released upon acceptance of the paper

We analyse the density profiles of the stellar halo populations in eight Milky-Way mass galaxies, simulated within the $\Lambda$-Cold Dark Matter scenario. We find that accreted stars can be well-fitted by an Einasto profile, as well as any subsample defined according to metallicity. We detect a clear correlation between the Einasto fitting parameters of the low-metallicity stellar populations and those of the dark matter haloes. The correlations for stars with [Fe/H]$, Comment: 5 pages,3 figures, MNRAS Letters accepted

The standard disc formation scenario postulates that disc forms as the gas cools and flows into the centre of the dark matter halo, conserving the specific angular momentum. Major mergers have been shown to be able to destroy or highly perturb the disc components. More recently, the alignment of the material that is accreted to form the galaxy has been pointed out as a key ingredient to determine galaxy morphology. However, in a hierarchical scenario galaxy formation is a complex process that combines these processes and others in a non-linear way so that the origin of galaxy morphology remains to be fully understood. We aim at exploring the differences in the formation histories of galaxies with a variety of morphology, but quite recent merger histories, to identify which mechanisms are playing a major role. We analyse when minor mergers can be considered relevant to determine galaxy morphology. We also study the specific angular momentum content of the disc and central spheroidal components separately. We used cosmological hydrodynamical simulations that include an effective, physically motivated supernova feedback that is able to regulate the star formation in haloes of different masses. We analysed the morphology and formation history of a sample of 15 galaxies of a cosmological simulation. We performed a spheroid-disc decomposition of the selected galaxies and their progenitor systems. The angular momentum orientation of the merging systems as well as their relative masses were estimated to analyse the role played by orientation and by minor mergers in the determination of the morphology. We found the discs to be formed by conserving the specific angular momentum in accordance with the classical disc formation model. The specific angular momentum of the stellar central spheroid correlates with the dark matter halo angular momentum and determines a power law. Abridged, 10 pages, 9 figures, A&A in press

Galaxy evolution is well constrained up to the first billion years of the Universe. Beyond this limit and considering the few number of sources with z >6.0 confirmed, it appears difficult to constrain the role played by the first galaxies during this period. One of the main goal of this thesis was to study the evolution of the luminosity function for star forming galaxies during the first billion years by using a representative sample of high-redshift objects (z >4.5) bright enough to be observed by spectroscopy. Thus, we have analyzed two different fields of view: one behind the lensing cluster A2667 and another one behind a large blank field (the WUDS survey). The analysis of the A2667 field showed a contamination rate of our sample of about 80%. We combined our observations with far IR data. Using these new data, we highlighted the existence of an extreme type of galaxies strongly affected by dust, which can only be removed from high-z samples by adding data in the far infra-red domain. Using spectroscopic follow up, we have detected another kind of contaminant at low-z combining two different stellar populations with different ages, and which cannot be removed from our sample excepted by using very deep images in the optical bands beyond the limits of current observations. From our samples we were able to add strong constraints on the bright-end of the luminosity function, and then we deduced its evolution during the first billion years of the Universe. Evolution of the LF allows us to deduce the UV density produced by these galaxies during the cosmic reionization, and to show that the relatively bright galaxies currently detected can not be the sole contributors.; L'évolution des galaxies est relativement bien contrainte jusqu'au premier milliard d'années de l'Univers. Au delà de cette limite et compte-tenu du faible nombre de sources confirmées à z>6.0, il est difficile de déterminer le rôle joué par les premières galaxies à cette époque. L'objectif de ce travail de thèse était de déterminer l'évolution de la fonction de luminosité des galaxies au cours du premier milliard d'années en se basant sur un échantillon représentatif d'objets à grand redshift (z>4.5) suffisamment brillant pour être observé par les spectrographes actuels. Dans ce but, nous avons réalisé une sélection photométrique ciblée de galaxies à cassure de Lyman dans deux champs de vue : un premier autour de l'amas de galaxies d'Abell 2667 et un second dans un très grand champ vide (le relevé WUDS). L'étude des données prises autour d'Abell 2667 a montré un taux de contamination d'environ 80% de notre échantillon d'objets à z≈8. Nous avons mis en évidence l'existence d'une population atypique de galaxies fortement rougies par la poussière à z≈2, et qui ne peuvent être écartées des échantillons qu'en ajoutant des contraintes dans l'IR lointain. Les observations spectroscopiques ont permis d'identifier un nouveau type de contaminant à bas redshift combinant deux populations stellaires d'âges très différents, et demandant une profondeur photométrique extrême afin de les exclure des échantillons actuels. A partir des échantillons dégagés nous avons pu apporter des contraintes fortes et indépendantes sur la partie brillante de la fonction de luminosité, et ainsi en déduire de façon homogène son évolution au cours du premier milliard d'années de l'Univers.

In the first part of the manuscript, I present the results on the properties of the interstellar medium and the stellar content of galaxies at z=0.6, from a representative sample of distant galaxies observed with the long slit spectrograph VLT/FORS2. This study has been realized in the framework of the ESO large program IMAGES "Intermediate MAss Galaxy Evolution Sequences", which aims to investigate the evolution of the main global properties of galaxies up to z 0.9. I discuss the implications of the observed chemical enrichment of the gas on the scenarios of galaxy formation. I also propose a new method to estimate reliable stellar masses in starburst galaxies using broadband photometry and their total star-formation rate. In a second part, I present a new method to extract, with high accuracy, the sky in spectra acquired with a fiber-fed instrument. I have developed this code in the Framwork of the phase A of an instrument proposed for the E-ELT : OPTIMOS-EVE. This is a multi-fiber, able to observe at optical and infrared wavelengths simultaneously. In the third part, I show preliminary results from the CENTRA GEPI- survey at Calar Alto Observaotry to study nearby galaxies, hosts of type Ia supernovae, using integral field spectroscopy. I present the first 2D maps of the gas and stellar populations of SNe Ia hosts. The results allow us to directly access the host properties in the immediate vinicity of the SNe Ia. This is a crucial step to invistigate eventual correlations between galaxy properties and SNe Ia events and evolution, leading to systematic effects on the derivation of the cosmological parameters., La première partie de cette thèse étudie la formation et l'évoluion des galaxies. Cette étude s'est réalisée dans le cadre du relevé IMAGES "Intermediate Mass Galaxy Evolution Sequences" qui a pour but de contraindre l'évolution des propriétés globales des galaxies de masses intermédiaires, de 1.5 à 15 x 1010 M⊙, de z=0.9 jusqu'à aujourd'hui. Un échantillon représentatif de galaxies distantes du "Chandra Deep Field South" (CDFS) a été observé avec le spectrographe intégral de champs GIRAFFE au VLT et le spectrographe à fente FORS2 également au VLT. Je suis responsable au sein de l'équipe IMAGES de l'exploitation des données FORS2. Je présente dans ce manuscrit les propriétés du milieu interstellaire sur un échantillon représentatif de 88 galaxies distantes. En comparant ces observations avec les propriétés des galaxies locales, je montre que les galaxies ont évolué de façon isolée, en convertissant leur gaz en étoiles, durant les derniers 8 milliards d'années. Aucun apport de gaz extérieur ni d'expulsion de matière interstellaire n'est nécessaire pour expliquer leur évolution récente. Ces conclusions se basent sur l'évolution de la relation fondamentale masse - métallicité, de la fraction de gaz, ainsi que de la non détection de vent stellaire intense dans les profiles des raies d'émission du gaz ionisé. Parallèlement à l'étude du milieu interstellaire, je me suis également intéressée au contenu en étoiles des galaxies. J'ai développé une méthode capable d'estimer la masse stellaire de galaxies actives en formation stellaire à partir de leur distribution spectral d'énergie. Le principe de cette méthode est de découper la lumière de la galaxie selon ses différentes composantes contribuant à la masse stellaire : étoiles jeunes, dáge intermédiaire et vieille, ainsi que l'effet de la poussière. Ce problème est dégénéré mais l'ajout du taux de formation stellaire comme une nouvelle contrainte permet de lever un grand nombre de dégénérescences. Lors de ma thèse, j'ai eu l'opportunité de travailler sur un projet instrumental en phase A pour le European Extremely Large Telescope (E-ELT) : le spectrographe multi-objet OPTIMOS-EVE. Mon rôle dans le consortium OPTIMOS-EVE a été d'implémenter une méthode capable d'extraire le bruit du ciel des données avec une erreur inférieure à 1% au niveau du continu du ciel. La méthode choisie est basée sur la reconstruction des variations spatiales du ciel sur tout le champ de vue de l'instrument à partir d'un échantillonnage partiel du ciel avec des fibres dédiées. Cette méthode permet d'extraire du ciel des raies très faibles. Ainsi, une raie d'émission avec un flux de 10-19erg/s/cm2 sur un continu de mangitude 30 en bande J peut être extraite du ciel (Mj = 18) avec un signal à bruit supérieur à 8 après 40h de temps d'exposition. La dernière partie de cette thèse est consacrée à l'étude des propriétés physiques des hôtes de Supernovae du type Ia (SN Ia). De récents modèles théoriques d'explosion de SN Ia montrent que les constances cosmologiques dérivées à partir des SN Ia peuvent être affectées par des biais issus des propriétés intrinsèques des SN Ia, tels que la métallicité et l'âge du progéniteur lors de l'explosion. L'étude directe des progéniteurs de SN Ia n'est pas réalisable actuellement, mais une première approximation de leurs caractéristiques peut être obtenue à partir de l'étude de leurs galaxies hôtes. Nous avons initié un relevé en spectroscopie intégral de champ de galaxies locales, hôtes de supernova. Je présente l'étude d'une galaxie hôte.

Only ~10% of baryons in the universe are in the form of stars, yet most models of luminous structure formation have concentrated on the properties of the luminous stellar matter. In this paper we focus on the "flip side" of galaxy formation and investigate the properties of the material that is not presently locked up in galaxies. This "by-product" of galaxy formation can be observed as an X-ray emitting plasma (the intracluster medium, hereafter ICM) in groups and clusters, and we present a version of the Durham semi-analytic galaxy formation model GALFORM that allows us to investigate the properties of the ICM. As we would expect on the basis of gravitational scaling arguments, the previous model (presented in Bower et al. 2006) fails to reproduce even the most basic observed properties of the ICM; however, we present a simple modification to the model to allow for heat input into the ICM from the AGN "radio mode" feedback. This heating acts to expel gas from the X-ray luminous central regions of the host halo. With this modification, the model reproduces the observed gas mass fractions and luminosity-temperature relation of groups and clusters. Introducing the heating process into the model requires changes to a number of model parameters in order to retain a good match to the observed galaxy properties. With the revised parameters, the best fitting luminosity function is comparable to that presented in Bower et al. (2006). The new model makes a fundamental step forward, providing a unified model of galaxy and cluster ICM formation. However, the detailed comparison with the data is not completely satisfactory, and we highlight key areas for improvement., 14 pages, 8 bit mapped figures. Version as published in MNRAS (for copy with high quality figures go to http://star-www.dur.ac.uk/~rgb/Bower08/xray_final_rev.pdf)

We investigate the dependence of galaxy clustering on luminosity and spectral type using the 2dF Galaxy Redshift Survey (2dFGRS). Spectral types are assigned using the principal component analysis of Madgwick et al. We divide the sample into two broad spectral classes: galaxies with strong emission lines (`late-types'), and more quiescent galaxies (`early-types'). We measure the clustering in real space, free from any distortion of the clustering pattern due to peculiar velocities, for a series of volume-limited samples. The projected correlation functions of both spectral types are well described by a power law for transverse separations in the range 2 < (sigma/Mpc/h) < 15, with a marginally steeper slope for early-types than late-types. Both early and late types have approximately the same dependence of clustering strength on luminosity, with the clustering amplitude increasing by a factor of ~2.5 between L* and 4 L*. At all luminosities, however, the correlation function amplitude for the early-types is ~50% higher than that of the late-types. These results support the view that luminosity, and not type, is the dominant factor in determining how the clustering strength of the whole galaxy population varies with luminosity., accepted by MNRAS after minor revision. 13 pages, 10 figures