We investigate the uses of gravitational lensing for analysing the dark matter haloes around galaxies, comparing galaxies within groups and clusters to those in the field. We consider two cases: when only photometric redshift data is available, and when spectroscopic redshift data is available for a sufficiently large sample of galaxies. For the case of data with photometric redshifts, we analyse the CFHTLenS dataset. This dataset is derived from the CFHTLS-Wide survey, and encompasses 154 deg^2 of high-quality shape data. Using the photometric redshifts to estimate local density, we divide the sample of lens galaxies with stellar masses in the range 10^9 Msun to 10^10.5 Msun into those likely to lie in high-density environments (HDE) and those likely to lie in low-density environments (LDE). Through comparison with galaxy catalogues extracted from the Millennium Simulation, we show that the sample of HDE galaxies should primarily (~61%) consist of satellite galaxies in groups, while the sample of LDE galaxies should consist of mostly (~87%) non-satellite (field and central) galaxies. Comparing the lensing signals around samples of HDE and LDE galaxies matched in stellar mass, we show that the subhaloes of HDE galaxies are less massive than those around LDE galaxies by a factor 0.65+/-0.12, significant at the 2.9 sigma level. A natural explanation is that the haloes of satellite galaxies are stripped through tidal effects in the group environment. Our results are consistent with a typical tidal truncation radius of ~40 kpc. For the case of data with spectroscopic redshifts, we analyse the GAMA-I and the ongoing GAMA-II surveys. We demonstrate the possibility of detecting tidal stripping of dark matter subhaloes within galaxy groups using weak gravitational lensing. We have run ray-tracing simulations on galaxy catalogues from the Millennium Simulation to generate mock shape catalogues. The ray-tracing catalogues assume a halo model for galaxies and groups, using various models with different distributions of mass between galaxy and group haloes to simulate different stages of group evolution. Using these mock catalogues, we forecast the lensing signals that will be detected around galaxy groups and satellite galaxies, as well as test two different methods for isolating the satellites' lensing signals. A key challenge is to determine the accuracy to which group centres can be identified. We show that with current and ongoing surveys, it will possible to detect stripping in groups of mass 10^12 Msun to 10^15 Msun.

The ubiquity of Lyman alpha (Ly alpha) emission in a sample of four bright [O III]- strong star-forming galaxies with redshifts above seven has led to the suggestion that such luminous sources represent a distinct population compared with their fainter, more numerous counterparts. The presence of Lya emission within the reionization era could indicate that these sources created early ionized bubbles due to their unusually strong radiation, possibly because of the presence of active galactic nuclei. To test this hypothesis, we secured long integration spectra with XSHOOTER on the VLT for three z similar or equal to 7 sources selected to have similar luminosities and prominent excess fluxes in the IRAC 3.6 or 4.5 mu m band, usually attributed to strong [O III] emission. We secured additional spectroscopy for one of these galaxies at z = 7.15 using MOSFIRE at the Keck telescope. For the most well-studied source in our sample with the strongest IRAC excess, we detect significant nebular emission from He II and N V indicative of a non-thermal source. For the other two sources at z = 6.81 and z = 6.85, for which no previous optical/near-infrared spectroscopy was available, Ly alpha is seen in one and C III] emission in the other. Although based on a modest sample, our results further support the hypothesis that the phenomenon of intense [O III] emission is associated preferentially with sources lying in early ionized bubbles. However, even though one of our sources at z = 7.15 suggests the presence of non-thermal radiation, such ionized bubbles may not uniquely arise in this manner. We discuss the unique advantages of extending such challenging diagnostic studies with JWST.

Measurements of the Hubble constantH(z) are increasingly being used to test the expansion rate predicted by various cosmological models. But the recent application of two-point diagnostics, such as Om(zi, zj) and Omh(2)(zi, zj), has produced considerable tension between Lambda CDM's predictions and several observations, with other models faring even worse. Part of this problem is attributable to the continued mixing of truly model-independent measurements using the cosmic-chronometer approach, and model-dependent data extracted from baryon acoustic oscillations. In this paper, we advance the use of two-point diagnostics beyond their current status, and introduce new variations, which we call Delta h(zi, zj), that are more useful for model comparisons. But we restrict our analysis exclusively to cosmic-chronometer data, which are truly model independent. Even for these measurements, however, we confirm the conclusions drawn by earlier workers that the data have strongly non-Gaussian uncertainties, requiring the use of both 'median' and 'mean' statistical approaches. Our results reveal that previous analyses using two-point diagnostics greatly underestimated the errors, thereby misinterpreting the level of tension between theoretical predictions and H(z) data. Instead, we demonstrate that as of today, only Einstein-de Sitter is ruled out by the two-point diagnostics at a level of significance exceeding similar to 3s. The R-h = ct universe is slightly favoured over the remaining models, including Lambda cold dark matter and Chevalier-Polarski-Linder, though all of them (other than Einstein-de Sitter) are consistent to within 1 sigma with the measured mean of the Delta h(zi, zj) diagnostics.

Until recently, obtaining rest-frame optical spectra of galaxies at z > 1 was a time consuming and challenging observation due to the difficult nature of near-infrared (near-IR) spectroscopy. However, with the advent of second generation ground-based near-IR spectrographs (e.g. KMOS, MOSFIRE), and the new low resolution near-IR grisms on the Hubble Space Telescope (HST), we have entered a new era in the study of high redshift galaxies. This thesis explores the physical properties of star-forming galaxies in the redshift range 1 < z < 3 by utilising a custom reduction of the 3D-HST near-IR grism spectroscopic survey. One of the most important observational constraints on the evolution of galaxies is the mass-metallicity relation (MZR), which is sensitive to both the star-formation history and various inflow/outflow processes. I use the 3D-HST spectra to provide a new constraint on the MZR at 2:0 < z < 2:3, and moreover measure the O/H abundance directly from the oxygen and hydrogen emission lines ([OII], [OIII] and Hβ) as opposed to the more common method at high redshift of inferring O/H from the N/H ratio (via [NII] and Hα). I show that the traditional form of the MZR is recovered from the 3D-HST data, with metallicity increasing with the stellar mass of a galaxy. However, the absolute metallicity values I derive are inconsistent with previous N/H-based measurements of metallicity at these redshifts. Moreover, I show that the 3D-HST data is inconsistent with the `fundamental metallicity relation' (FMR), and that, contrary to previous claims, this local Universe relation may not hold out to z & 2. To investigate this metallicity discrepancy further, I measure the evolution of the [OIII]/Hβ nebular emission line ratio in the 3D-HST spectra over the redshift range 1:3 < z < 2:3. I compare this observed line ratio evolution with state-of-the- art theoretical models which take into account the independent evolution of the ionization parameter, electron density and metallicity of star-forming regions with redshift. The homogeneous 3D-HST dataset allows me to perform a consistent analysis of this evolution which takes into account line luminosity selection effects. I show that, according to models, the observed [OIII]/Hβ evolution cannot be accounted for by pure metallicity evolution. Instead I am able to infer that the line ratio evolution is more consistent with, at the very least, an evolution to stronger ionizing conditions at high redshift, and perhaps even denser star-forming regions. I explore how this result can also explain the observed discrepancy between high redshift metallicity measurements. In light of this finding, I revisit the MZR at z >~ 2 and employ a purely theoretical approach to inferring metallicities from nebular lines, which is able to account for an evolution in ionization conditions. I then use a selection of galaxies from the local Universe, which mimic the properties of high redshift galaxies, to derive a more robust ionization sensitive, conversion, between N/H and O/H. With this new conversion which I am able to bring the previous inconsistent metallicity measurements at z >~ 2 back into agreement. Finally, I am able to show that, in this new formalism, the metallicity evolution between z = 2 and z = 3 is perhaps not as large as previously reported. To conclude I discuss ongoing work as part of the KMOS Deep Survey (KDS) being undertaken with the near near-IR Multi-Object Spectrograph KMOS on the VLT. I describe the observations and data reduction that has been completed to date and describe how this instrument will allow me to extend the work presented in this thesis to z > 3. I also introduce FIGS, a new HST near-IR grism survey seeking to spectroscopically identify galaxies at 5:5 < z < 8:5 and work I have begun in exploring this dataset.

Les études détaillées d'amas de galaxies confirmés à grands redshifts sont peu nombreuses. L’objectif de cette Thèse est d’établir le premier catalogue d'amas confirmés spectroscopiquement à grand redshift et, pour la première fois à ces redshifts, d’étudier de manière statistique les propriétés des galaxies membres des amas. Dans cette Thèse, nous caractérisons et étudions 20 candidats amas à redshifts 1.4 < z < 2.8 parmi les candidats les plus prometteurs de l’échantillon CARLA. Nous réduisons et analysons des données spectroscopiques grism sans fente et imagerie proche-infrarouge des amas candidats, obtenues avec le télescope spatial Hubble. Nous mesurons plus de 700 redshifts au sein des champs observés, et confirmons spectroscopiquement 16 amas CARLA dans l’intervalle 1.4 < z < 2.8; ces amas sont associés à des noyaux galactiques actifs à fortes émissions radios (RLAGN) en leur centre, par sélection. Cet effort fait plus que doubler le nombre d’amas confirmés à ces redshifts. Nous étudions également le taux de formation stellaire des galaxies membres des amas en fonction de leur masses stellaires, et de la distance aux RLAGN. Nous trouvons que les galaxies membres massives sont situées sous la séquence principale jusqu’à z=2, ce qui suggère déjà à ces redshifts une évolution accélérée des galaxies massives au sein des amas. Nous trouvons également une concentration plus importante de membres actifs à plus petits rayons des RLAGN, jusqu’à z=2. Ceci est en accord avec un renversement de la relation densité vs. taux de formation stellaire pour nos amas CARLA à 1.4 < z < 2.0, ce qui suggère que les amas CARLA représentent une phase de transition de l’évolution des galaxies au sein des amas. Nous étudions également les populations stellaires de deux de nos amas confirmés à redshift z=2.0. Nous analysons les relations couleurs-couleurs et couleurs-magnitudes de ces deux amas et montrons que l’une des structures à z=2 possède une séquence rouge de galaxies passives. Globalement, nos résultats démontrent que les amas CARLA représentent des structures riches comprenant des populations mixtes de galaxies évoluées et massives sans formation stellaire, et des galaxies actives formant des étoiles. Cet échantillon sans précédent de 16 amas confirmés spectroscopiquement dans l’intervalle de redshift 1.4 < z < 2.8 constitue un échantillon idéal pour étudier statistiquement la phase de transition des amas de galaxies, ainsi que les mécanismes de suppression de la formation stellaire. (Abrégé) / Detailed studies of high-redshift confirmed galaxy clusters are based on a few individual objects. In this Thesis, we therefore aim at building the first sample of spectroscopically confirmed clusters at high-redshifts and, for the first time at these redshifts, statistically infer cluster member galaxy properties. In this Thesis, we study and characterize 20 cluster candidates at redshifts 1.4 < z < 2.8, which represent the most promising cluster candidates from the CARLA sample. We reduce and analyze slitless grism spectroscopic and near-infrared imaging data of the fields, obtained with the Hubble Space Telescope. We measure redshifts for over 700 star-forming sources in the 20 fields, and we spectroscopically confirm 16 CARLA clusters in the range 1.4 < z < 2.8; by selection, these clusters are associated with powerful radio-loud active galactic nuclei (RLAGN) at their center. This effort alone more than doubles the number of confirmed clusters at these redshifts. We study cluster member star-formation rates (SFRs) as a function of their stellar masses and distances from the RLAGN. We find that massive members are located below their star-forming main-sequence up to z=2. This implies that the massive star-forming end of the cluster population already followed an accelerated evolution at these high redshifts. We also find an increasing concentration of star-forming members with smaller radii relative to the RLAGN, at all redshifts up to z=2. Our 1.4 < z < 2.0 cluster members are therefore consistent with a reversal of the SFR-density relation. This is a first evidence showing that CARLA clusters represent a transition phase for cluster galaxy evolution. We also study stellar populations of two of our confirmed CARLA clusters at z=2.0. We study their color-color and color-magnitude relations and show that one of the two structures is comprised of a z=2 red sequence of passive candidate members. Together, these results provide clear evidence that our confirmed CARLA clusters represent rich structures comprised of mixed populations, including both evolved, passive, massive galaxies, and galaxies with ongoing star formation. Together, this unprecedented sample of 16 confirmed clusters at 1.4 < z < 2.8 constitutes an ideal sample for further statistical investigation of the cluster transition phase, including study of quenching mechanisms. (Abridged)

Il y a presque dix ans que l'accélération de l'expansion de l'Univers a été mise en évidence grâce aux observations des supernovae de type Ia et du fonds diffus cosmologique. Cette découverte a changé notre compréhension du contenu énergétique de l'Univers puisque pour expliquer une telle accélération, une composante supplémentaire de matière (effective ou non) est nécessaire et contribue à hauteur de 70%. Cette dernière est appelé "énergie noire". Elle affecte aussi bien les mesures de distance, que la croissance des sur-densités de matières primordiales qui donnent naissance aux structures. Les principales sondes sensibles à ces deux dernières quantités sont les supernovae de type Ia, les amas de galaxies, les lentilles gravitationnelles, et les oscillations acoustiques des baryons (BAO). Afin de contraindre précisément les modèles théoriques (Constante Cosmologique, modification de la théorie de la relativité générale par exemple) qui tentent de déterminer la nature de l'énergie noire, l'observation de chacune de ces quatre sondes est indispensable. Le niveau de précision sur la mesure des paramètres des modèles d'énergie noire requis est tel qu'une nouvelle génération d'instruments va voir le jour dans les années à venir avec notamment le télescope LSST (Large Synoptic Survey Telescope). Le télescope LSST dont le miroir primaire fait 8.4 mètres de diamètre, produira un sondage couvrant la moitié du ciel observable dans 6 bandes photométriques pendant 10 ans. Sa caméra sera la plus grosse caméra jamais construite dans le monde avec un plan focal de 3.2 milliards de pixels. Cette thèse présente à la fois un aspect expérimental et phénoménologique. Le travail présenté porte tout d'abord sur l'élaboration du banc d'étalonnage de la caméra de LSST, et des premières mesures optiques validant le schéma de principe du banc. Nous présenterons ensuite la simulation des BAO dédiée à LSST tentant de prédire à quelle précision les paramètres d'énergie noire pourront être contraint. L'accent est mis sur la production d'un catalogue photométrique de galaxies simulé ainsi que sur une méthode de calcul des redshifts photométriques. La validation de la méthode grâce à des données spectro-photométriques du CFHTLS est également présentée.

In Yoshii et al., we described a new method for measuring extragalactic distances based on dust reverberation in active galactic nuclei (AGNs), and we validated our new method with Cepheid variable stars. In this Letter, we validate our new method with Type Ia supernovae (SNe Ia) that occurred in two of the AGN host galaxies during our AGN monitoring program: SN 2004bd in NGC 3786 and SN 2008ec in NGC 7469. Their multicolor light curves were observed and analyzed using two widely accepted methods for measuring SN distances, and the distance moduli derived are m= 33.47 +/- 0.15 for SN 2004bd and 33.83 +/- 0.07 for SN 2008ec. These results are used to obtain independently the distance measurement calibration factor, g. The g value obtained from the SN Ia discussed in this Letter is gSN= 10.61 +/- 0.50, which matches, within the range of 1s uncertainty, gDUST = 10.60, previously calculated ab initio in Yoshii et al. Having validated our new method for measuring extragalactic distances, we use our new method to calibrate reverberation distances derived from variations of Ha emission in the AGN broad-line region, extending the Hubble diagram to z approximate to 0.3 where distinguishing between cosmologies is becoming possible.

>Magister Scientiae - MSc / I combine 610 MHz Giant Metrewave Radio Telescope (GMRT) data, 1.4 GHz Very Large Array (VLA) data and 1.4 GHz Westerbork Synthesis Radio Telescope (WSRT) observations, encompassing a ∼ 4 square degree field (sq. deg. field) centred on the verification strip of the Spitzer First Look Survey (FLS) field (RA = 17h18m00s, Dec = 59◦30′30′′), to study radio sources down to fluxes of about 0.1 mJy. The results of an analysis of a sample of 107 multi-component radio sources obtained by cross-correlating the VLA and GMRT catalogues are shown. The spectral index analysis shows that the majority of multi-component sources are steep-spectrum sources. Nevertheless the spread in the spectral distribution is wide, with a significant number of ultrasteep,flat or inverted sources. By cross-correlating 107 multi-component radio sources with the optical catalogues of Marleau et al. (2007) and Papovich et al. (2006), 23 objects were identified and spectroscopically classified as galaxies. Some of them are classified as star-forming or star-burst galaxies, perhaps indicating that AGN and starformation activity are ongoing in the same galaxy. The measured redshifts span the range 0 < z < 1.8 and peak at z ∼ 0.2. According to their radio power (P), 6 of the identified objects are in the range of FR II sources (P1.4GHz > 1024.5W/Hz) while 17 are in the range of FR I sources (P1.4GHz < 1024.5W/Hz). Most of the sources having P1.4GHz < 1024.5W/Hz are compact and few are extended and peculiar, while all sources in the range of P1.4GHz > 1024.5W/Hz are extended. Further optical followup is recommended to allow a more complete census of the sub-mJy population and more information on AGN feedback from such sources.

Le modèle ΛCDM de la cosmologie repose sur l’existence d’une composante exotique, appelée énergie noire, pour expliquer l’accélération tardive de l’expansion de l’univers à z < 0.7. Des alternatives à cette constante cosmologique proposent de modifier la théorie de la gravitation basée sur la relativité générale aux échelles cosmologiques. Depuis l’automne 2014, le multi-spectrographe SDSS-eBOSS effectue un relevé de quasars dans un domaine en redshift peu exploré entre 0.8 ≤ z ≤ 2.2 dont l’un des objectifs majeurs est d’étendre les contraintes sur la nature de l’énergie noire et de tester la validité de la théorie de la relativité générale à plus haut redshift en utilisant les quasars comme traceurs de la matière.Dans cette thèse, nous mesurons et analysons la fonction de corrélation à deux points de l’échantillon de quasars obtenu après deux ans d'observation de eBOSS pour contraindre les distances cosmiques, à savoir la distance angulaire DA et le taux d'expansion H, ainsi que le taux de croissance des structures fσ8 à un redshift effectif Zeff = 1.52. Nous commençons par construire des catalogues des grandes structures qui prennent en compte la géométrie angulaire et radiale du relevé. Puis pour obtenir des contraintes robustes, nous identifions plusieurs sources d’effets systématiques, en particulier ceux liés à la modélisation et aux observations sont étudiées avec des « mock catalogues » dédiés qui correspondent à des réalisations fictives de l’échantillon de quasars eBOSS. Les paramètres cosmologiques de ces catalogues fictifs étant connus, ils sont utilisés comme référence pour tester notre procédure d’analyse. Les résultats de ce travail sur l’évolution des distances cosmiques sont compatibles avec les prédictions du modèle ΛCDM utilisant les paramètres de Planck et basé sur l’existence d’une constante cosmologique. La mesure du taux de croissance des structures est compatible avec la prédiction de ce modèle basé sur la relativité générale, ce qui étend ainsi la validité de la théorie aux échelles cosmologiques à grand redshift. Nous utilisons également notre mesure pour mettre à jour les contraintes sur les modèles d'extensions à ΛCDM et sur les scénarios de gravité modifiée. Ce travail de thèse constitue une première étude menée avec les données de quasars eBOSS et sera utilisée pour l’analyse de l’échantillon final à la fin 2019 ou l’on attend une amélioration de la précision statistique d’un facteur 2. Associé à BOSS, eBOSS ouvrira la voie pour les futurs programmes d’observation, comme le télescope au sol DESI et le satellite Euclid. Ces deux programmes sonderont intensivement l’époque de l’univers entre 1 < z < 2 en observant plusieurs millions de spectres, ce qui permettra d'améliorer d'un ordre de grandeur au moins les contraintes actuelles sur les paramètres cosmologiques. / The ΛCDM model of cosmology assumes the existence of an exotic component, called dark energy, to explain the late-time acceleration of the expansion of the universe at redshift z < 0.7. Alternative scenarios to this cosmological constant suggest to modify the theory of gravitation based on general relativity at cosmological scales. Since fall 2014, the SDSS-IV eBOSS multi-object spectrograph has undertaken a survey of quasars in the almost unexplored redshift range 0.8 ≤ z ≤ 2.2 with the key science goal to complement the constraints on dark energy and extend the test of general relativity at higher redshifts by using quasars as direct tracers of the matter field.In this thesis work, we measure and analyse the two-point correlation function of the two-year data taking of eBOSS quasar sample to constrain the cosmic distances, i.e. the angular diameter distance DA and the expansion rate H, and the growth rate of structure fσ8 at an effective redshift Zeff = 1.52. First, we build large-scale structure catalogues that account for the angular and radial incompleteness of the survey. Then to obtain robust results, we investigate several potential systematics, in particular modeling and observational systematics are studied using dedicated mock catalogs which are fictional realizations of the data sample. These mocks are created with known cosmological parameters such that they are used as a benchmark to test the analysis pipeline. The results on the evolution of distances are consistent with the predictions for ΛCDM with Planck parameters assuming a cosmological constant. The measurement of the growth of structure is consistent with general relativity and hence extends its validity to higher redshift. We also provide updated constraints on extensions of ΛCDM and models of modified gravity. This study is a first use of eBOSS quasars as tracers of the matter field and will be included in the analysis of the final eBOSS sample at the end of 2019 with an expected improvement on the statistical precision of a factor 2. Together with BOSS, eBOSS will pave the way for future programs such as the ground-based Dark Energy Spectroscopic Instrument (DESI) and the space-based mission Euclid. Both programs will extensively probe the intermediate redshift range 1 < z < 2 with millions of spectra, improving the cosmological constraints by an order of magnitude with respect to current measurements.

Il y a presque dix ans que l'accélération de l'expansion de l'Univers a été mise en évidence grâce aux observations des supernovae de type Ia et du fonds diffus cosmologique. Cette découverte a changé notre compréhension du contenu énergétique de l'Univers puisque pour expliquer une telle accélération, une composante supplémentaire de matière (effective ou non) est nécessaire et contribue à hauteur de 70%. Cette dernière est appelé «énergie noire». Elle affecte aussi bien les mesures de distance, que la croissance des sur-densités de matières primordiales qui donnent naissance aux structures. Les principales sondes sensibles à ces deux dernières quantités sont les supernovae de type Ia, les amas de galaxies, les lentilles gravitationnelles, et les oscillations acoustiques des baryons (BAO). Afin de contraindre précisément les modèles théoriques (Constante Cosmologique, modification de la théorie de la relativité générale par exemple) qui tentent de déterminer la nature de l'énergie noire, l'observation de chacune de ces quatre sondes est indispensable. Le niveau de précision sur la mesure des paramètres des modèles d'énergie noire requis est tel qu'une nouvelle génération d'instruments va voir le jour dans les années à venir avec notamment le télescope LSST (Large Synoptic Survey Telescope). Le télescope LSST dont le miroir primaire fait 8.4 mètres de diamètre, produira un sondage couvrant la moitié du ciel observable dans 6 bandes photométriques pendant 10 ans. Sa caméra sera la plus grosse caméra jamais construite dans le monde avec un plan focal de 3.2 milliards de pixels. Cette thèse présente à la fois un aspect expérimental et phénoménologique. Le travail présenté porte tout d'abord sur l'élaboration du banc d'étalonnage de la caméra de LSST, et des premières mesures optiques validant le schéma de principe du banc. Nous présenterons ensuite la simulation des BAO dédiée à LSST tentant de prédire à quelle précision les paramètres d'énergie noire pourront être contraint. L'accent est mis sur la production d'un catalogue photométrique de galaxies simulé ainsi que sur une méthode de calcul des redshifts photométriques. La validation de la méthode grâce à des données spectro-photométriques du CFHTLS est également présentée. / More than ten years ago, the accelerated expansion of the Universe was discovered, by type Ia supernovae, and then confirmed by other probes. This discovery has changed our understanding of the energetic content of the Universe. Indeed, in order to explain such an acceleration, a new component has to be introduced and it must contribute to 70% of the total energy density. This component, the so called Dark Energy, affects both cosmological distances and the growth of structures from which galaxies originates. The main cosmological probes of dark energy are the type Ia supernovae, the galaxy cluster count, the weak gravitational lensing and the baryon acoustic oscillations (BAO). In order to precisely constrain theoretical models, such as the cosmological constant, a modify gravity or a new scalar field, joint observations of all four probes are very efficient. The required accuracy on cosmological measurements is so high that a new generation of instruments is growing, among which the Large Synoptic Survey Telescope (LSST). The telescope, with a primary mirror of 8.4 m diameter, will cover half of the optical sky in six photometric bandpasses. Its camera will be the world biggest camera ever constructed with a focal plane array composed of 3.2 Gpixels. This thesis treats both the experimental and phenomenological aspects. Firstly, the work presented here consists in the development of the LSST camera calibration optical bench. We have designed a system allowing an efficient commissioning of the camera before its installation on the telescope, and a precise calibration of the focal plane. Preliminary measurements validating the design of the bench will be presented. Secondly, a detailed Baryon Acoustic Oscillations simulation dedicated to LSST will be introduced. Its main goal is to predict the level of precision on the dark energy equation of state parameter reconstruction that will be reached with LSST. We will stress on the production of a mock photometric galaxy catalog and on the photometric redshifts computation. A validation of the method on real spectro-photometric from CFHTLS will also be shown.