The expansion of the universe is currently accelerating, as first inferred by Efstathiou et al. (1990), Ostriker & Steinhardt (1995) and directly determined by Riess et al. (1998) and Perlmutter et al. (1999). Current constraints are consistent with a time independent equation-of-state of w = -1, which is to be expected when a constant vacuum energy density dominates. But the Quantum Field Theory prediction for the magnitude of this vacuum energy is very much larger than that inferred (Weinberg, 1989; Koksma & Prokopec, 2011). It is entirely possible that the cause of the expansion has an alternative explanation, with both the inclusion of a quantum scalar field and modified gravity theories able to reproduce an expansion history close to, but potentially deviating from, that of a cosmological constant and cold dark matter. In this work I investigate the consistency of the VIMOS Public Extragalactic Redshift Survey (VIPERS) v7 census of the galaxy distribution at z = 0:8 with the expansion history and linear growth rate predicted by General Relativity (GR) when a Planck Collaboration et al. (2016) fiducial cosmology is assumed. To do so, I measure the optimally weighted redshift-space power spectrum (Feldman et al., 1994), which is anisotropic due to the coherent infall of galaxies towards overdensities and outflow from voids (Kaiser, 1987). The magnitude of this anisotropy can distinguish between modified theories of gravity as the convergence (divergence) rate of the velocity field depends on the effective strength of gravity on cosmological scales (Guzzo et al., 2008). This motivates measuring the linear growth rate rather than the background expansion, which is indistinguishable for a number of modified gravity theories. In Chapter 6 I place constraints of fσ8(0:76) = 0:44 ± 0:04; fσ8(1:05) = 0:28 ± 0:08; with the completed VIPERS v7 survey; the combination remains consistent with General Relativity at 95% confidence. The dependence of the errors on the assumed priors will be investigated in future work. Further anisotropy is introduced by the Alcock-Paczynski effect - a distortion of the observed power spectrum due to the assumption of a fiducial cosmology differing from the true one. These two sources of anisotropy may be separated based on their distinct scale and angular dependence with sufficiently precise measurements. Doing so degrades the constraints: fσ8(0:76) = 0:31 ± 0:10; fσ8(1:05) = -0:04 ± 0:26; but allows for the background expansion (FAP ≡ (1 + z)DAH=c) to be simultaneously constrained. Galaxy redshift surveys may then directly compare both the background expansion and linear growth rate to the GR predictions I find the VIPERS v7 joint-posterior on (fσ8; FAP ) shows no compelling deviation from the GR expectation although the sizeable errors reduce the significance of this conclusion. In Chapter 4 I describe and outline corrections for the VIPERS spectroscopic selection, which enable these constraints to be made. The VIPERS selection strategy is (projected) density dependent and may potentially bias measures of galaxy clustering. Throughout this work I present numerous tests of possible systematic biases, which are performed with the aid of realistic VIPERS mock catalogues. These also allow for accurate statistical error estimates to be made { by incorporating the sample variance due to both the finite volume and finite number density. Chapter 5 details the development and testing of a new, rapid approach for the forward modelling of the power spectrum multipole moments obtained from a survey with an involved angular mask. An investigation of the necessary corrections for the VIPERS PDR-1 angular mask is recorded. This includes an original derivation for the integral constraint correction for a smoothed, joint-field estimate of ¯n(z) and a description of how the mask should be accounted for in light of the Alcock- Paczynski effect. Chapter 7 investigates the inclusion of a simple local overdensity transform: 'clipping' prior to the redshift-space distortions (RSD) analysis. This tackles the root cause of non-linearity and potentially extends the validity of perturbation theory. Moreover, this marked clustering statistic potentially amplifies signatures of modified gravity and, as a density-weighted two-point statistic, includes information not available to the power spectrum. I show that a linear real-space power spectrum with a Kaiser factor and a Lorentzian damping yields a significant bias without clipping, but that this may be removed with a sufficiently strict transform; similar behaviour is observed for the VIPERS v7 dataset. Estimates of fσ8 for different thresholds are highly correlated due to the overlapping volume, but the bias for insufficient clipping can be calibrated and the correlation obtained using mock catalogues. A maximum likelihood value for the combined constraint of a number of thresholds is shown to achieve a ' 16% decrease in statistical error relative to the most precise single-threshold estimate. The results are encouraging to date but represent a work in progress; the final analysis will be submitted to Astronomy & Astrophysics as Wilson et al. (2016). In addition to this, an original extension of the prediction for a clipped Gaussian field to a clipped lognormal field is presented. The results of tests of this model with a real-space cube populated according to the halo occupation distribution model are also provided.

Les principaux objectifs de cette thèse sont de valider, consolider et développer une nouvelle méthode permettant de mesurer la distribution en redshift d'un échantillon de galaxies. Là où les méthodes actuelles - redshifts spectroscopiques et photométriques - sont toutes liées à l'étude de la distribution d'énergie spectrale des sources extragalactiques, l'approche ici présentée repose sur les propriétés d'agrégation des galaxies entre elles. En effet l'agrégation (clustering en anglais) des galaxies due à la gravité leur confère une distribution spatiale - et angulaire - particulière. La méthode des clustering redshifts utilise cette propriété particulière d'agrégation entre une population de galaxies dont le redshift est inconnu et un échantillon d'objets de référence afin de déprojeter l'information et de reconstruire la distribution en redshift de la population inconnue. On peut s'attendre à ce que les systématiques de cette approche soient différentes de celles des méthodes existantes qui elles s'intéressent à la distribution spectrale d'énergie (SED) des galaxies. Ce type d'approche répond à un réel besoin de la part de la communauté scientifique dans le cadre des grands projets d'observations tels que la mission Euclid de l'Agence Spatiale Européenne (ESA). Après avoir situé le contexte scientifique général et avoir mis en évidence le rôle crucial de la mesure des distances en astronomie, je présente les outils statistiques généralement utilisés dans le cadre de l'étude de la répartition de la matière dans l'Univers ainsi que leur modification afin de pouvoir mesurer des distributions en redshift. Après avoir validé cette approche sur un type d'objets extragalactiques particuliers, j'ai ensuite étendu son application à l'ensemble des galaxies existantes. J'ai ensuite exploré la précision et les systématiques affectant ces mesures dans un cas idéal. Puis, je m'en suis éloigné de façon à me trouver en situation réelle. J'ai également poussé plus loin cette analyse et montré que les objets de référence utilisés lors de la mesure n'ont pas besoin de constituer un échantillon dont la magnitude limite est représentative de la population de redshift inconnu. Cette propriété constitue un avantage considérable pour l'utilisation de cette approche dans le cadre des futurs grands projets observationnels comme la mission spatiale Euclid. Pour finir, je résume mes principaux résultats et présente certains de mes futurs projets. / The main goals of this thesis are to validate, consolidate and develop a new method to measure the redshift distribution of a sample of galaxies. Where current methods - spectroscopic and photometric redshifts - rely on the study of the spectral energy distribution of extragalactic sources, the approach presented here is based on the clustering properties of galaxies. Indeed clustering of galaxies caused by gravity gives them a particular spatial - and angular - distribution. In this clustering redshift approach, we use this particular property between a galaxies sample of unknown redshifts and a galaxies sample of reference to reconstruct the redshift distribution of the unknown population. Thus, possible systematics in this approach should be independent of those existing in other methods. This new method responds to a real need from the scientific community in the context of large dark imaging experiments such as the Euclid mission of the European Space Agency (ESA). After introducing the general scientific context and having highlighted the crucial role of distance measurements in astronomy, I present the statistical tools generally used to study the large scale structure of the Universe as well as their modification to infer redshift distributions. After validating this approach on a particular type of extragalactic objects, I generalized its application to all types of galaxies. Then, I explored the precision and some systematic effects by conducting an ideal case study. Thus, I performed a real case study. I also pushed further this analysis and found that the reference sample used in the measurement does not need to have the same limiting magnitude than the population of unknown redshift. This property is a great advantage for the use of this approach in the context of large imaging dark energy experiments like the Euclid space mission. Finally, I summarize my main results and present some of my future projects.

We discuss new Keck/MOSFIRE spectroscopic observations of four luminous galaxies at z similar or equal to 7-9 selected to have intense optical line emission by Roberts-Borsani et al. Previous follow-up has revealed Ly alpha in two of the four galaxies. Our new MOSFIRE observations confirm that Lya is present in the entire sample. We detect Lya emission in the galaxy COS-zs7-1, confirming its redshift as z.(Ly alpha) = 7.154, and we detect Lya in EGS-zs8-2 at z(Ly alpha) = 7.477, verifying an earlier tentative detection. The ubiquity of Lya in this sample is puzzling given that the IGM is expected to be significantly neutral over 7 < z < 9. To investigate this result in more detail, we have initiated a campaign to target UV metal lines in the four Lya emitters as a probe of both the ionizing field and the Lya velocity offset at early times. Here we present the detection of C III] emission in the z = 7.73 galaxy EGS-zs8-1, requiring an intense radiation field and moderately low metallicity. We argue that the radiation field is likely to affect the local environment, increasing the transmission of Lya through the galaxy. Moreover, the centroid of C III] indicates that Lya is redshifted by 340 km s (1). This velocity offset is larger than that seen in less luminous systems, providing an explanation for the transmission of Lya emission through the IGM. Since the transmission is further enhanced by the likelihood that such systems are also situated in large ionized bubbles, the visibility of Lya at z > 7 is expected to be strongly luminosity-dependent, with transmission accelerated in systems with intense star formation.

Enormous Ly alpha nebulae (ELANe), unique tracers of galaxy density peaks, are predicted to lie at the nodes and intersections of cosmic filamentary structures. Previous successful searches for ELANe have focused on wide-field narrowband surveys or have targeted known sources such as ultraluminous quasi-stellar objects (QSOs) or radio galaxies. Utilizing groups of coherently strong Ly alpha absorptions, we have developed a new method to identify high-redshift galaxy overdensities and have identified an extremely massive overdensity, BOSS1441, at z = 2-3. In its density peak, we discover an ELAN that is associated with a relatively faint continuum. To date, this object has the highest diffuse Ly alpha nebular luminosity of L-nebula = 5.1 +/- 0.1 x 10(44) erg s(-1). Above the 2 sigma surface brightness limit of SBLy alpha = 4.8 x 10(-18) erg s(-1) cm(-2) arcsec(-2), this nebula has an end-to-end spatial extent of 442 kpc. This radio-quiet source also has extended C IV lambda 1549 and He II lambda 1640 emission on greater than or similar to 30 kpc scales. Note that the Ly alpha, He II, and C IV emissions all have double-peaked line profiles. Each velocity component has an FWHM of approximate to 700-1000 km s(-1). We argue that this Lya nebula could be powered by shocks due to an active galactic nucleus-driven outflow or photoionization by a strongly obscured source.

Powerful forces are at work in giant Ly α nebulae, a rare and mysterious population in the high redshift universe. Much like the spatially extended emission line halos around high redshift radio galaxies . but without the strong radio emission . Ly α nebulae (or Ly α 'blobs') boast copious Ly α emission (10⁴⁴ erg s⁻¹), large sizes (∼100 kpc), complex gas morphologies, and the company of numerous compact, star-forming galaxies, and may offer a window into dramatic episodes of massive galaxy formation. The small sample sizes and complex inner workings of Ly α nebulae have limited progress on understanding the their space density, environments, and physical conditions. This thesis strives to answer fundamental questions about Ly α nebulae and pave the way for understanding their role in the build up of massive galaxy systems. To address the frequency of collapse of these massive structures, we carried out the largest systematic Ly α nebula survey to date and measured the Ly α nebula space density. As an unbiased test of the environment of Ly α nebulae, we studied the surroundings of a Ly α nebula and confirmed that Ly α nebulae reside preferentially in overdense regions. To disentangle the sources of ionization, we took a census of all the compact ionization sources within a large Ly α nebula using high resolution imaging. Finally, we used photoionization modeling to put constraints on the physical conditions, the metallicity, and the sources of ionization within Ly α nebulae. Future work will be able to build on this thesis by expanding the systematic search for Ly α nebulae to other existing deep broad-band datasets, mapping the three-dimensional overdense structures in which Ly α nebulae live out to ≥ 50 (comoving) Mpc scales, and disentangling multiple sources of ionization within a larger sample of individual systems using deep optical and near-infrared spectroscopy and detailed photoionization modeling.

We test the galactic outflow model by probing associated galaxies of four strong intergalactic C IV absorbers at z = 5-6 using the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) ramp narrowband filters. The four strong C IV absorbers reside at z = 5.74, 5.52, 4.95, and 4.87, with column densities ranging from N-C IV = 10(13.8) to 10(14.8) cm(-2). At z = 5.74, we detect an i-dropout Ly alpha emitter (LAE) candidate with a projected impact parameter of 42 physical kpc from the C IV absorber. This LAE candidate has a Ly alpha-based star formation rate (SFRLy alpha) of 2 M-circle dot yr(-1) and a UV-based SFR of 4 M-circle dot yr(-1). Although we cannot completely rule out that this i-dropout emitter may be an [O II] interloper, its measured properties are consistent with the C IV powered galaxy at z = 5.74. For C IV absorbers at z = 4.95 and z = 4.87, although we detect two LAE candidates with impact parameters of 160 and 200 kpc, such distances are larger than that predicted from the simulations. Therefore, we treat them as nondetections. For the system at z = 5.52, we do not detect LAE candidates, placing a 3 sigma upper limit of SFRLy alpha approximate to 1.5 M-circle dot yr(-1). In summary, in these four cases, we only detect one plausible C IV source at z = 5.74. Combining the modest SFR of the one detection and the three nondetections, our HST observations strongly support that smaller galaxies (SFRLy alpha less than or similar to 2 M-circle dot yr(-1)) are main sources of intergalactic C IV absorbers, and such small galaxies play a major role in the metal enrichment of the intergalactic medium at z greater than or similar to 5.

Quasars are galaxies hosting accreting supermassive black holes; due to their brightness, they are unique probes of the early universe. To date, only a few quasars have been reported at z > 6.5 (< 800 Myr after the big bang). In this work, we present six additional z greater than or similar to 6.5 quasars discovered using the Pan-STARRS1 survey. We use a sample of 15 z greater than or similar to 6.5 quasars to perform a homogeneous and comprehensive analysis of this highest-redshift quasar population. We report four main results: (1) the majority of z greater than or similar to 6.5 quasars show large blueshifts of the broad C IV lambda 1549 emission line compared to the systemic redshift of the quasars, with a median value similar to 3x higher than a quasar sample at z similar to 1; (2) we estimate the quasars' black hole masses (M-BH similar to (0.3-5) x. 10(9) M circle dot) via modeling of the Mg II lambda 2798 emission line and rest-frame UV continuum and find that quasars at high redshift accrete their material (with <(Lbol L-Edd)> = 0.39) at a rate comparable to a luminosity-matched sample at lower redshift, albeit with significant scatter (0.4 dex); (3) we recover no evolution of the Fe II/Mg II abundance ratio with cosmic time; and (4) we derive near-zone sizes and, together with measurements for z similar to 6 quasars from recent work, confirm a shallow evolution of the decreasing quasar near-zone sizes with redshift. Finally, we present new millimeter observations of the [C II] 158 mu m emission line and underlying dust continuum from NOEMA for four quasars and provide new accurate redshifts and [C II]/infrared luminosity estimates. The analysis presented here shows the large range of properties of the most distant quasars.

Early quiescent galaxies at z similar to 2 are known to be remarkably compact compared to their nearby counterparts. Possible progenitors of these systems include galaxies that are structurally similar, but are still rapidly forming stars. Here, we present Karl G. Jansky Very Large Array (VLA) observations of the CO(1-0) line toward three such compact, star-forming galaxies (SFGs) at z similar to 2.3, significantly detecting one. The VLA observations indicate baryonic gas fractions. greater than or similar to 5 times lower and gas depletion timescales. greater than or similar to 10 times shorter than normal, extended massive SFGs at these redshifts. At their current star formation rates, all three objects will deplete their gas reservoirs within 100 Myr. These objects are among the most gas-poor objects observed at z > 2, and are outliers from standard gas scaling relations, a result that remains true regardless of assumptions about the CO-H-2 conversion factor. Our observations are consistent with the idea that compact, SFGs are in a rapid state of transition to quiescence in tandem with the buildup of the z similar to 2 quenched population. In the detected compact galaxy, we see no evidence of rotation or that the CO-emitting gas is spatially extended relative to the stellar light. This casts doubt on recent suggestions that the gas in these compact galaxies is rotating and significantly extended compared to the stars. Instead, we suggest that, at least for this object, the gas is centrally concentrated, and only traces a small fraction of the total galaxy dynamical mass.

We present the rationale for and the observational description of ASPECS: the ALMA SPECtroscopic Survey in the Hubble Ultra-Deep Field (UDF), the cosmological deep field that has the deepest multi-wavelength data available. Our overarching goal is to obtain an unbiased census of molecular gas and dust continuum emission in high-redshift (z > 0.5) galaxies. The similar to 1' region covered within the UDF was chosen to overlap with the deepest available imaging from the Hubble Space Telescope. Our ALMA observations consist of full frequency scans in band. 3 (84-115 GHz) and band. 6 (212-272 GHz) at approximately uniform line sensitivity (L'(CO) similar to 2 x 10(9) K km s(-1) pc(2)), and continuum noise levels of 3.8 mu Jy beam(-1) and 12.7 ae Jy beam(-1), respectively. The molecular surveys cover the different rotational transitions of the CO molecule, leading to essentially full redshift coverage. The [C II] emission line is also covered at redshifts 6.0 < z < 8.0. We present a customized algorithm to identify line candidates in the molecular line scans. and quantify our ability to recover artificial sources from our data. Based on whether multiple CO lines are detected, and whether optical spectroscopic redshifts as well as optical counterparts exist, we constrain the most likely line identification. We report 10 (11) CO line candidates in the 3mm (1mm) band, and our statistical analysis shows that < 4 of these (in each band) are likely spurious. Less than one-third. of the total CO flux in the low-J CO line candidates are from sources that are not associated with an optical/NIR counterpart. We also present continuum maps of both the band. 3 and band. 6 observations. The data presented here form the basis of a number of dedicated studies that are presented in subsequent papers.

We present evidence for redshift quantization in the Lyman -a forest of several QSOs. The Ly -a data are at redshifts z from 1.89 to 3.74, and the theory of redshift quantization proposed by Cocke (1983, 1085) is used to scale the quantization interval (24.15 km s -') to these high redshift. The sealing depends on the deceleration parameter qo, and the quantization is present at a statistical significance of greater than 99% for qo = 1/2. This may be taken as confirming the inflationary model of the early history of the universe. The significance of the quantization is highest at go rs 0.48, and the width of the peak is about 0.03 . The result can also be seen as providing confirmatory evidence for both the theory of the redshift quantization and the above value of qo, but at a significance of only 03 %. The scenario proposed for the relativistic generalization of the theory is that of fermion wavefunctione and quantum operators in a background Riemannian spacetime satisfying Einstein's field equations.