Les amas de galaxies sont des outils cosmologiques et astrophysiques essentiels, car ce sont les objets les plus grands et les plus massifs gravitationnellement liées dans l'Univers. L'étude de leur fonction de masse, de leur fonction de corrélation et des relations d'échelle entre leur masse et différentes observables nous permettent de tester les prévisions des modèles cosmologique et les scenarii de formation des structures. Ils sont aussi d'intéressants laboratoires pour l'étude de la formation et de l'évolution des galaxies, et de leur interactions avec le milieu qui les entourent, dans d’environnements denses. Pour y parvenir, estimer précisément leur masse revêt une importance fondamentale. J’ai étudié la précision de la richesse optique calculée par l’algorithme de détection d’amas RedGOLD (Licitra et al. 2016) en tant que mass proxy, en utilisant des mesures de lentilles gravitationnelles (weak lensing) et des observations en rayon X. J’ai mesuré les masses cumulées d’un échantillon de 1323 amas de galaxies dans le CFHTLS et NGVS à 0.2<z<0.5, dans l’intervalle de richesse 10-70. J'ai testé différents modèles prenant en compte les erreurs sur la position du centre de l'amas, les effets de lentille non faible (non-weak shear), le "two-halo term", la contribution de la galaxie centrale brillante et la dispersion intrinsèque de la relation masse-richesse. J'ai montré que la correction de la position du centre est nécessaire pour éviter un biais dans la mesure de la masse, alors que l'ajout de la galaxie centrale n'affecte pas les résultats. J'ai calculer les coefficients de la relation masse-richesse et ceux de la relation d'échelle entre masses issues du weak lensing et celle estimées à partir d'observations dans les rayons X. Mes résultats sont en accord avec les simulations et les précédents travaux publiés. / Galaxy clusters are essential cosmological and astrophysical tools, since they represent the largest and most massive gravitationally bound structures in the Universe. Through the study of their mass function, of their correlation function, and of the scaling relations between their mass and different observables, we can probe the predictions of cosmological models and structure formation scenarios. They are also interesting laboratories that allow us to study galaxy formation and evolution, and their interactions with the intra-cluster medium, in dense environments. For all of these goals, an accurate estimate of cluster masses is of fundamental importance. I studied the accuracy of the optical richness obtained by the RedGOLD cluster detection algorithm (Licitra et al. 2016) as a mass proxy, using weak lensing and X-ray mass measurements. I measured stacked weak lensing cluster masses for a sample of 1323 galaxy clusters in the CFHTLS W1 and in the NGVS at 0.2<z<0.5, in the optical richness range 10-70. I tested different weak lensing mass models that account for miscentering, non-weak shear, the two-halo term, the contribution of the Brightest Cluster Galaxy, and the intrinsic scatter in the mass-richness relation. I found that the miscentering correction is necessary to avoid a bias in the measured halo masses, while the inclusion of the BCG mass does not affect the results. I calculated the coefficients of the mass-richness relation, and of the scaling relations between the lensing mass and X-ray mass proxies. My results are consistent with simulations and previous works in the literature.

In dieser Dissertation nutze ich den Gravitationslinseneffekt, um eine Reihe von kosmologischen Fragen zu untersuchen. Der Laufzeitunterschied des Gravitationslinsensystems HE1104-1805 wurde mit unterschiedlichen Methoden bestimmt. Zwischen den beiden Komponenten erhalte ich einen Unterschied von Delta_t(A-B) = -310 +-20 Tagen (2 sigma Konfidenzintervall).<br /> Außerdem nutze ich eine dreijährige Beobachtungskampagne, um den Doppelquasar Q0957+561 zu untersuchen. Die beobachteten Fluktuationen in den Differenzlichtkurven lassen sich durch Rauschen erklären, ein Mikrogravitationslinseneffekt wird zur Erklärung nicht benötigt. Am Vierfachquasar Q2237+0305 untersuchte ich den Mikrogravitationslinseneffekt anhand der Daten der GLITP-Kollaboration (Okt. 1999-Feb. 2000). Durch die Abwesenheit eines starken Mikrogravitationslinsensignals konnte ich eine obere Grenze von v=600 km/s f für die effektive Transversalgeschwindigkeit der Linsengalaxie bestimmen (unter der Annahme von Mikrolinsen mit 0.1 Sonnenmassen). <br /> Im zweiten Teil der Arbeit untersuchte ich die Verteilung der Dunklen Materie in Galaxienhaufen. Für den Galaxienhaufen Cl0024+1654 erhalte ich ein Masse-Leuchtkraft-Verhältnis von M/L = 200 M_sun/L_sun (innerhalb eines Radius von 3 Bogenminuten). Im Galaxienhaufen RBS380 finde ich eine relativ geringe Röntgenleuchtkraft von L =2*10^(44) erg/s, obwohl im optischen eine große Anzahl von Galaxien gefunden wurde. / In this thesis the gravitational lensing effect is used to explore a number of cosmological topics. We determine the time delay in the gravitationally lensed quasar system HE1104-1805 using different techniques. We obtain a time delay Delta_t(A-B) Delta_t(A-B) =-310 +- 20 days (2 sigma errors) between the two components. We also study the double quasar Q0957+561 during a three years monitoring campaign. The fluctuations we find in the difference light curves are completely consistent with noise and no microlensing is needed to explain these fluctuations. Microlensing is also studied in the quadruple quasar Q2237+0305 during the GLITP collaboration (Oct.1999-Feb.2000). We use the absence of a strong microlensing signal to obtain an upper limit of v=600 km/s for the effective transverse velocity of the lens galaxy (considering microlenses with 0.1 solar masses). The distribution of dark matter in galaxy clusters is also studied in the second part of the thesis. In the cluster of galaxies Cl0024+1654 we obtain a mass-to-light ratio of M/L = 200 M_sun/L_sun (within a radius of 3 arcminutes). In the galaxy cluster RBS380 we find a relatively low X-ray luminosity for a massive cluster of L =2*10^(44) erg/s, but a rich distribution of galaxies in the optical band.

In my thesis I investigate the luminous z ~ 3 Lyman break galaxies in deep wide field surveys. In the first part of the thesis, I use the LBT/LUCIFER to observe a lensed high-redshift star-forming galaxy (J0900+2234) at z = 2.03. With the high S/N near-IR spectroscopic observations, I reveal the detailed physical properties of this high-redshift galaxy, including SFR, metallicity, dust extinction, dynamical mass, and electron number density. In the second part of the thesis, I select a large sample of LBGs at z ~ 3 from our new LBT Bootes field survey, and study the bright end luminosity function (LF), stellar mass function (SMF) and clustering properties of bright LBGs (1L* < L < 2.5L*). Together with other LF and SMF measurements, the evolution of LF and SMF can be well described by continuously rising star formation history model. Using the clustering measurements in this work and other works, a tight relation between the average host galaxy halo mass and the galaxy star formation rate is found, which can be interpreted as arising from cold flow accretion. The relation also suggests that the cosmic star formation efficiency is about 5%-20% of the total cold flow mass. This cosmic star formation efficiency does not evolve with redshift (from z ~ 5 to z ~ 3), hosting dark matter halo mass (10¹¹-10¹³ M⊙), or galaxy luminosity (from 0.3L* to 3L*).In the third and fourth parts, with the spectroscopic follow-up observations of the bright LBGs, I establish a sample of spectroscopically-confirmed ultra-luminous LBGs (ULBGs) in NOAO Bootes field. With this new ULBG sample, the rest-frame UV LF of LBG at M(1700Å) = -23.0 was measured for the first time. I find that the ULBGs have larger outflow velocity, broader Lyα emission and ISM absorption line profiles, and more prominent CIV P-Cygni profile. This profile may imply a top-heavy IMF in these ULBGs. The ULBGs have larger stellar mass and SFR, but smaller dust extinction than the typical L* LBGs at z ~ 2 - 3. We proposed two evolutionary scenarios, pre-burst and post-burst. The properties of the ULBGs, especially the morphologies, prefer the pre-starburst scenario. Further high spatial resolution HST imaging and IFU spectroscopic observations will allow us to distinguish these two scenarios.

This dissertation addresses two cosmological applications of the Lyman-alpha (Ly ɑ) forest observed in QSO pairs separated by several arcminutes or less. The Ly ɑ flux autocorrelation and cross-correlation provide a measurement of cosmic geometry at z > 2, via a variant of the Alcock-Paczyński test. I present the results of an observing campaign to obtain moderate resolution spectroscopy of the Ly ɑ forest in QSO pairs with small redshift differences (Δz < 0.25) and arcminute separations (θ < 5'). This new sample includes 29 pairs and one triplet suitable for measuring the cross-correlation and 78 individual QSO spectra for determining the autocorrelation. Continuum fits are provided, as are seven revisions for previously published QSO identifications and/or redshifts. Using a suite of hydrodynamic simulations, anisotropies in the Ly ɑ flux correlation function due to redshift-space distortions and spectral smoothing are investigated for 1:8 ≤ z ≤ 3, further enabling future applications of the Alcock-Paczyński test with Ly ɑ correlation measurements. Sources of systematic error including limitations in mass-resolution and simulation volume, prescriptions for galactic outflow, and the observationally uncertain mean flux decrement are considered. The latter is found to be dominant. An approximate solution for obtaining the zero-lag cross-correlation for arbitrary spectral resolution is presented, as is a method for implementing the resulting anisotropy corrections while mitigating systematic uncertainty.

High power diode-pumped solid state (DPSS) lasers are a rapidly growing technology that is attractive for various applications in scientific and industrial fields. DPSS lasers are highly efficient, reliable and durable with superior beam quality when compared to flash-lamp pumped lasers. Double-tungstate crystals such as potassium yttrium tungstate Yb:KY(WO₄)₂ (Yb:KYW) are one of the most popular active materials used in DPSS lasers for generation of continuous wave radiation and ultrashort (i.e. femtosecond, 10⁻¹⁵ s) pulses with high average output power. The high pump power of laser diodes results in considerable heat generation in a laser crystal that in turn causes thermal lensing effect. Thermal lensing affects the performance and stability of a resonator, and plays an important role in limiting the output power and degrading the beam quality of solid state lasers. Despite these facts, no detailed studies of thermal effects in Yb:KYW lasers were reported to date. In this work thermal lensing in a diode-pumped Ng-cut Yb:KYW laser operating at the wavelength of 1.04 μm was characterized. A maximum output power of 3.5 W with a nearly diffraction limited output beam (M₂ < 1.2) was achieved under the absorbed pump power of 13.8 W. The focal lengths of the induced thermal lenses were obtained from the laser output beam size measurements at various incident pump power levels and ABCD matrix analysis. At maximum output power the focal length of the induced thermal lens was found to be 814 mm for the Nm direction (horizontal) and 144 mm for the Np direction (vertical). Thermal lens sensitivity factors were 1.26 m⁻¹/W and 0.32 m⁻¹/W for the Np and Nm directions, respectively. This highly astigmatic thermal lensing can be explained by strong anisotropy of thermo-optical properties of the crystal and its cooling geometry. In addition, the finite element analysis (FEA) method was employed to obtain the focal lengths of the induced thermal lens inside the crystal. Simulation results obtained from the theoretical model were compared to experimental data, and the accuracy of the model was verified. The results of this work are critical for practical design of the efficient and reliable Yb:KYW lasers with multi-Watt average output power.

High power diode-pumped solid state (DPSS) lasers are a rapidly growing technology that is attractive for various applications in scientific and industrial fields. DPSS lasers are highly efficient, reliable and durable with superior beam quality when compared to flash-lamp pumped lasers. Double-tungstate crystals such as potassium yttrium tungstate Yb:KY(WO₄)₂ (Yb:KYW) are one of the most popular active materials used in DPSS lasers for generation of continuous wave radiation and ultrashort (i.e. femtosecond, 10⁻¹⁵ s) pulses with high average output power. The high pump power of laser diodes results in considerable heat generation in a laser crystal that in turn causes thermal lensing effect. Thermal lensing affects the performance and stability of a resonator, and plays an important role in limiting the output power and degrading the beam quality of solid state lasers. Despite these facts, no detailed studies of thermal effects in Yb:KYW lasers were reported to date. In this work thermal lensing in a diode-pumped Ng-cut Yb:KYW laser operating at the wavelength of 1.04 μm was characterized. A maximum output power of 3.5 W with a nearly diffraction limited output beam (M₂ < 1.2) was achieved under the absorbed pump power of 13.8 W. The focal lengths of the induced thermal lenses were obtained from the laser output beam size measurements at various incident pump power levels and ABCD matrix analysis. At maximum output power the focal length of the induced thermal lens was found to be 814 mm for the Nm direction (horizontal) and 144 mm for the Np direction (vertical). Thermal lens sensitivity factors were 1.26 m⁻¹/W and 0.32 m⁻¹/W for the Np and Nm directions, respectively. This highly astigmatic thermal lensing can be explained by strong anisotropy of thermo-optical properties of the crystal and its cooling geometry. In addition, the finite element analysis (FEA) method was employed to obtain the focal lengths of the induced thermal lens inside the crystal. Simulation results obtained from the theoretical model were compared to experimental data, and the accuracy of the model was verified. The results of this work are critical for practical design of the efficient and reliable Yb:KYW lasers with multi-Watt average output power.

A variety of precision observations suggest that the present universe is dominated by some unknown components, the so-called dark matter and dark energy. The distribution and properties of these components are the focus of modern cosmology and we are only beginning to understand them. Gravitational lensing, the bending of light in the gravitational field of a massive object, is one of the predictions of the general theory of relativity. It has become an ever more important tool for investigating the dark universe, especially with recent and coming advances in observational data. This thesis studies gravitational lensing effects on scales ranging over ten orders of magnitude to probe very different aspects of the dark universe. Implementing a matter distribution following the predictions of recent simulations, we show that microlensing by a large population of massive compact halo objects (MACHOs) is unlikely to be the source of the observed long-term variability in quasars. We study the feasibility of detecting the so far elusive galactic dark matter substructures, the so-called “missing satellites”, via millilensing in galaxies close to the line-of-sight to distant light sources. Finally, we utilise massive galaxy clusters, some of the largest structures known in the universe, as gravitational telescopes in order to detect distant supernovae, thereby gaining insight into the expansion history of the universe. We also show, how such observations can be used to put constraints on the dark matter component of these galaxy clusters. / At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 6: Submitted.

A network of laser interferometer gravitational waves detectors spread across the globe is currently running and steadily improving. After complex data analysis from the output signal of the present detectors, astrophysical results begin to emerge with upper limits on gravitational wave sources. So far, however no direct detection has been announced. To increase the sensitivity of current detectors, a second generation of interferometers is planned which will make gravitational wave astronomy a reality within one decade. The advanced generation of interferometers will represent a substantial upgrade from current detectors. Especially, very high optical power will circulate in the arm cavities in order to reduce by one order of magnitude the shot noise limited sensitivity in high frequency. However, the theoretical shot noise limit will only be achieved after implementation of complex thermal lensing compensation schemes. Thermal lensing is direct consequence of the residual optical absorption inside the substrate and coating of the test masses and could have tragic consequences for the functionality of the interferometer. The Australian Consortium for Interferometric Gravitational Astronomy (ACIGA) in collaboration with LIGO will run a series of high optical power tests to understand the characteristics and effects of thermal lensing. During these tests, techniques to compensate thermal lensing will be experimented. This thesis mainly focused on the first high optical power test in Gingin, Australia. The first test will consist of a Fabry Perot cavity with the sapphire substrate of the input mirror inside the cavity. Due to the high optical circulating power a strong convergent thermal lens will appear in the input mirror substrate. Because of the presence of the thermal lens inside the cavity, the size of the cavity waist will be reduced and the cavity circulating power will decrease. Simulations using higher order mode expansion and FFT propagation code were completed to estimate ways to compensate strong thermal lensing for the Gingin first test. The term `strong thermal lensing? is used because the thermal lens focal length is comparable to the design focal length of the optical components. The expected performance of a fused silica compensation plate is presented and advantages and limits of this method are discussed. Experimental results on small scale actuators which can potentially compensate thermal lensing are detailed. The knowledge gained from these experiments was valuable to design the real scale compensation plate which was used in the first Gingin test. This test was carried at the end of 2005. The thermal lens due to 1 kW of optical power circulating in the sapphire substrate was successfully compensated using a fused silica plate. Yet, thermal lensing compensation may only be required for room temperature advanced interferometer. Indeed, we showed that cooling the interferometer mirror to cryogenic temperature can eliminate the thermal lensing problem and also substantially decrease the mirror thermal noise.

Dusty star forming galaxies (DSFGs), characterized by their far-infrared (far-IR) emission, undergo the largest starbursts in the Universe, contributing to the majority of the cosmic star formation rate density at z = 1−4. The Herschel Space Observatory for the first time was able observe the full far-IR dust emission for a large population of high-redshift DSFGs, thereby accurately measuring their star formation rates. With gravitational lensing, we are able to surpass the Herschel confusion limit and probe intrinsically less luminous and therefore more normal star-forming galaxies. With this goal in mind, we have conducted a large Herschel survey, the Herschel Lensing Survey, of the cores of almost 600 massive galaxy clusters, where the effects of gravitational lensing are the strongest. In this thesis, I present follow-up studies of gravitationally lensed Herschel-detected DSFGs by utilizing multi-wavelength data from optical to radio. Specifically, I characterize the star forming properties of gravitationally lensed DSFGs by using these three subsamples: (1) A gravitationally lensed DSFG galaxy at z = 0.6 in one of the most massive galaxy clusters, Abell S1063 (at z = 0.3), (2) One of the brightest sources in HLS, which is a system of two strongly gravitationally lensed galaxies, one at z = 2.0 (optically faint gravitational arc) and the other at z = 4.7 (triply-imaged galaxy), (3) A sample of the brightest sources in HLS at z = 1−4, in which we detect rest-frame optical nebular emission lines (e.g. Hα, Hβ, [OIII]λλ4959,5007) by utilizing near-IR spectroscopy. The main results from these studies are as follows: (1) In the cluster-lensed DSFG at z = 0.6, discovered in the core of Abell S1063, we identify a luminous (SFR = 10 M⊙/yr) giant (D~1 kpc) HII region similar to those typically found at higher redshift (z~2). We show that the HII region is embedded in a rotating disk and likely formed in isolation, rather than through galaxy interaction, which is observed in local galaxies. We can use this source as a nearby laboratory for star forming regions at z ~ 2, in which more detailed follow-up of this source can help us to understand their origin/properties. (2) We discovered that one of the brightest sources in HLS is a blend of two cluster-lensed DSFGs, one at z = 2.0 (an optically faint arc) and the other at z = 4.7 (triply-imaged galaxy), implying that a sample of bright Herschel sources may have such multiplicity. In the z = 2.0 arc, the sub-arcsecond clumps detected in the SMA image surprisingly do not correspond to the clumps in the JVLA CO(1-0) image. When investigating the CO(1-0) velocity structure, there is a substantial amount of molecular gas (likely a molecular wind/outflow) we find that we find is not associated with star formation. This suggests that the CO morphology in DSFGs could be strongly influenced by molecular outflows resulting in the over-prediction of the amount of the molecular gas available for star formation. In the z = 2.0 arc, we also constrain αCO~4. While this value is normal for galaxies like the Milky Way, it is quite unusual for ULIRGs. This hints that the physical conditions may be much different in the arc from other ULIRGs, which usually have αCO ≈ 0.8.(3) We successfully detect rest-frame optical emission lines in 8 gravitationally lensed DSFGs at z = 1−4 using ground-based near-IR spectroscopy with Keck, LBT and Magellan. The luminosities of these lines are substantially less than what the far-IR derived star formation rates predict, suggesting that these DSFGs have large dust attenuations. The difference in the star formation rates is a factor of 30 x (AV= 4), which is larger than previously reported for DSFGs at z > 1. One galaxy (z = 1.5) in the sample showed the largest suppression with a factor of 550x (AV = 7), which is similar to local ULIRGs. Future prospects: Herschel provided a glimpse into the star formation of DSFGs, but only the brightest at z > 2 could be studied in detail without gravitational lensing. ALMA will revolutionize the study of DSFGs with its high spatial resolution submm/mm imaging of their dust continuum and molecular gas, and it will begin to unravel their physical properties. In order to detect nebular emission lines in fainter higher redshift sources, 20-30 meter class telescopes, with next generation near-IR spectrographs, will be necessary. JWST will play a significant role as it will target rest-frame optical nebular emission lines in DSFGs unobtainable from the ground as well as weaker Hydrogen series lines (such as Paschen and Brackett series) to better understand their instantaneous star formation and dust attenuation.

We study a sample of 19 galaxy clusters in the redshift range 0.15 < z < 0.30 with highly complete spectroscopic membership catalogues (to K < K*(z) + 1.5) from the Arizona Cluster Redshift Survey, individual weak-lensing masses and near-infrared data from the Local Cluster Substructure Survey, and optical photometry from the Sloan Digital Sky Survey. We fit the scaling relations between total cluster luminosity in each of six bandpasses (grizJK) and cluster mass, finding cluster luminosity to be a promising mass proxy with low intrinsic scatter sigma ln (L|M) of only similar to 10-20 per cent for all relations. At fixed overdensity radius, the intercept increases with wavelength, consistent with an old stellar population. The scatter and slope are consistent across all wavelengths, suggesting that cluster colour is not a function of mass. Comparing colour with indicators of the level of disturbance in the cluster, we find a narrower variety in the cluster colours of 'disturbed' clusters than of 'undisturbed' clusters. This trend is more pronounced with indicators sensitive to the initial stages of a cluster merger, e.g. the Dressler Schectman statistic. We interpret this as possible evidence that the total cluster star formation rate is 'standardized' in mergers, perhaps through a process such as a system-wide shock in the intracluster medium.