We present a sample of similar to 1000 emission-line galaxies at z = 0.4-4.7 from the similar to 0.7deg(2) High-z Emission-Line Survey in the Bootes field identified with a suite of six narrow-band filters at approximate to 0.4-2.1 mu m. These galaxies have been selected on their Ly alpha (73), [O (II)] (285), H beta/[O (III)] (387) or H alpha (362) emission line, and have been classified with optical to near-infrared colours. A subsample of 98 sources have reliable redshifts from multiple narrow-band (e.g. [O (II)]-H alpha) detections and/or spectroscopy. In this survey paper, we present the observations, selection and catalogues of emitters. We measure number densities of Ly alpha, [O (II)], H beta/[O (III)] and H alpha and confirm strong luminosity evolution in star-forming galaxies from z similar to 0.4 to similar to 5, in agreement with previous results. To demonstrate the usefulness of dual-line emitters, we use the sample of dual [O (II)]-H alpha emitters to measure the observed [O (II)]/H alpha ratio at z = 1.47. The observed [O (II)]/H alpha ratio increases significantly from 0.40 +/- 0.01 at z = 0.1 to 0.52 +/- 0.05 at z = 1.47, which we attribute to either decreasing dust attenuation with redshift, or due to a bias in the (typically) fibre measurements in the local Universe that only measure the central kpc regions. At the bright end, we find that both the H alpha and Ly alpha number densities at z approximate to 2.2 deviate significantly from a Schechter form, following a power law. We show that this is driven entirely by an increasing X-ray/active galactic nucleus fraction with line luminosity, which reaches approximate to 100 per cent at line luminosities L greater than or similar to 3 x 10(44) erg s(-1).

We present a study of the relation between galaxy stellar age and mass for 14 members of the z = 1.62 protocluster IRC 0218, using multiband imaging and HST G102 and G141 grism spectroscopy. Using UVJ colors to separate galaxies into star-forming and quiescent populations, we find that, at stellar masses M*>= 10(10.85)M circle dot the quiescent fraction in the protocluster is f(Q) = 1.0(-0.37)(+0.00), consistent with a similar to 2x enhancement relative to the field value, f(Q) = 0.45(-0.03)(+0.03). At masses 10(10.2)M circle dot <= M* <= 10(10.85)M circle dot, f(Q) in the cluster is f(Q) = 0.40(-0.18)(+0.20), consistent with the field value of f(Q) = 0.28(-0.02)(+0.02). Using galaxy D-n(4000) values derived from the G102 spectroscopy, we find no relation between galaxy stellar age and mass. These results may reflect the impact of merger- driven mass redistribution-which is plausible, as this cluster is known to host many dry mergers. Alternately, they may imply that the trend in f(Q) in IRC 0218 was imprinted over a short timescale in the protocluster's assembly history. Comparing our results with those of other high- redshift studies and studies of clusters at z similar to 1, we determine that our observed relation between f(Q) and stellar mass only mildly evolves between z similar to 1.6 and z similar to 1, and only at stellar masses M* <= 10(10.85) M circle dot Both the z similar to 1 and z similar to 1.6 results are in agreement that the red sequence in dense environments was already populated at high redshift, z greater than or similar to 3, placing constraints on the mechanism(s) responsible for quenching in dense environments at z >= 1.5.

We combine state-of-the-art models for the production of stellar radiation and its transfer through the interstellar medium (ISM) to investigate ultraviolet-line diagnostics of stars, the ionized and the neutral ISM in star-forming galaxies. We start by assessing the reliability of our stellar population synthesis modelling by fitting absorption-line indices in the ISM-free ultraviolet spectra of 10 Large Magellanic Cloud clusters. In doing so, we find that neglecting stochastic sampling of the stellar initial mass function in these young (similar to 10-100 Myr), low-mass clusters affects negligibly ultraviolet-based age and metallicity estimates but can lead to significant overestimates of stellar mass. Then, we proceed and develop a simple approach, based on an idealized description of the main features of the ISM, to compute in a physically consistent way the combined influence of nebular emission and interstellar absorption on ultraviolet spectra of star-forming galaxies. Our model accounts for the transfer of radiation through the ionized interiors and outer neutral envelopes of short-lived stellar birth clouds, as well as for radiative transfer through a diffuse intercloud medium. We use this approach to explore the entangled signatures of stars, the ionized and the neutral ISM in ultraviolet spectra of star-forming galaxies. We find that, aside from a few notable exceptions, most standard ultraviolet indices defined in the spectra of ISM-free stellar populations are prone to significant contamination by the ISM, which increases with metallicity. We also identify several nebular-emission and interstellar-absorption features, which stand out as particularly clean tracers of the different phases of the ISM.

We present CI(2-1) and multi-transition (CO)-C-12 observations of a dusty star-forming galaxy, ACT J2029+0120, which we spectroscopically confirm to lie at z = 2.64. We detect CO(3-2), CO(5-4), CO(7-6), CO(8-7), and CI (2-1) at high significance, tentatively detect HCO+(4-3), and place strong upper limits on the integrated strength of dense gas tracers (HCN(4-3) and CS(7-6)). Multi-transition CO observations and dense gas tracers can provide valuable constraints on the molecular gas content and excitation conditions in high-redshift galaxies. We therefore use this unique data set to construct a CO spectral line energy distribution (SLED) of the source, which is most consistent with that of a ULIRG/Seyfert or QSO host object in the taxonomy of the Herschel Comprehensive ULIRG Emission Survey. We employ RADEX models to fit the peak of the CO SLED, inferring a temperature of T similar to 117 K and n(H2) similar to 10(5) cm(-3), most consistent with a ULIRG/QSO object and the presence of high-density tracers. We also find that the velocity width of the C I line is potentially larger than seen in all CO transitions for this object, and that the L'(Ci(2-1))/L'(CO(3-2)) ratio is also larger than seen in other lensed and unlensed submillimeter galaxies and QSO hosts; if confirmed, this anomaly could be an effect of differential lensing of a shocked molecular outflow.

Les propriétés globales des galaxies montrent une forte évolution du taux de formation stellaire et de la densité de masse stellaire à l'époque de l'assemblage des galaxies précédent le pic de formation stellaire dans l'univers, produite par plusieurs processus physiques concurrents (fusion, accrétion, rétroaction, environnement, ...). Les propriétés morphologiques des galaxies ont aussi fortement évolué à la même époque. Dans cette thèse, j'étudie comment l'évolution des propriétés morphologique est reliée aux propriétés spectrophotométriques des galaxies depuis z ~ 6. Les données spectroscopiques obtenues au sein du VIMOS Ultra Deep Survey (VUDS), un nouveau sondage spectroscopique unique de ~ 10000 galaxies entre redshift z~2 et z~6 qui fournissent un excellent moyen de sonder l'évolution galactique à travers cette époque cosmique. A partir des mes résultats, je conclus que les différentes propriétés morphologiques de galaxies à formation stellaire aux redshifts 2<z<6 montrent qu'il existe plusieurs façons pour les galaxies de se former. La grande diversité de tailles, la fraction importante de super-amas d'étoiles et de gaz très lumineux indiquant des fusions et ceux moins lumineux résultant probablement d'instabilités dans la formation des disques galactiques, avec la prévalence de galaxies irrégulières couvrant un grand domaine de masse stellaire et formation stellaire, pointent ensemble un scénario ou l'assemblage des galaxies procéde de différents méchanismes physiques. La formation des galaxies apparait plus complexe qu'un scénario simple impliquant la formation d'un disque avec de l'accrétion de gaz pourrait le faire croire. / The global properties of galaxies show a strong evolution of the star formation rate and stellar mass density at the epoch of galaxy assembly, driven by several competing physical processes (merging, accretion, feedback, environment,...). The morphological properties of galaxies are also strongly evolving over the same timescales. I investigate how the evolution of the morphological properties is connected to the spectrophotometric properties of galaxies since z~6. The spectroscopic data obtained within the VIMOS Ultra Deep Survey (VUDS), a new unique spectroscopic survey of ~10000 galaxies between redshifts z~2 and z~6 conducted at the ESO-VLT, combined with the available Hubble Space Telescope imaging surveys such as COSMOS or CANDELS provide a great way of probing galactic evolution across this cosmic epoch.From the results that I have obtained, I conclude that the different morphological properties of star-forming galaxies at 2<z<6 show that there are several mechanisms that take part in galaxy formation. The great diversity in galaxy sizes, the high number of bright two clump systems as well as faint multi-clump systems indicating merger and disk instabilities processes, respectively, and the wide range in physical properties that are populated by irregular galaxies all point to a diverse history for galaxy formation. This suggests that forming galaxies is far more complex that the simple explanation of evolution from gas accretion alone.

Our sensitive (sigma(n) approximate to 572 nJy beam(-1)), high-resolution (FWHM theta(1/2) = 0"22 approximate to 2 kpc at z greater than or similar to 1), 10 GHz image covering a single Karl G.. Jansky Very Large Array (VLA) primary beam (FWHM circle minus(1/2) approximate to 4.'25) in the GOODS-N field contains 32 sources with S-p greater than or similar to 2 mu Jy beam(-1) and optical and/or near-infrared (OIR) counterparts. Most are about as large as the star-forming regions that power them. Their median FWHM major axis is <theta(M)>= 167 +/- 32 mas approximate to 1.2 +/- 0.28 kpc, with rms scatter approximate to 91 mas approximate to 0.79 kpc. In units of the effective radius re that encloses half their flux, these radio sizes are re approximate to 69 +/- 13 mas approximate to 509 +/- 114 pc, with rms scatter approximate to 38 mas approximate to 324 pc. These sizes are smaller than those measured at lower radio frequencies, but agree with dust emission sizes measured at mm/sub-mm wavelengths and extinction-corrected H alpha sizes. We made a lowresolution (theta(1/2) = 1."0) image with approximate to 10x better brightness sensitivity, in order to detect extended sources and measure matched-resolution spectral indices alpha(10 GHz)(1.4 GHz) 10 GHz. It contains six new sources with Sp. 3.9 mJy beam-1 and OIR counterparts. The median redshift of all 38 sources is similar to z similar to = 1.24 +/- 0.15. The 19 sources with 1.4 GHz counterparts have a median spectral index of <alpha(1.4 GHz) (10 GHz)> = -0.74 +/- 0.10 10 GHz, with rms scatter approximate to 0.35. Including upper limits on a for sources not detected at 1.4 GHz flattens the median to <alpha(1.4 GHz) (10 GHz)> greater than or similar to -0.61 10 GHz, suggesting that the mu Jy radio sources at higher redshifts-and hence those selected at higher rest-frame frequencies-may have flatter spectra. If the non-thermal spectral index is alpha(NT) approximate to -0.85, the median thermal fraction of sources selected at median rest-frame frequency approximate to 20 GHz is greater than or similar to 48%.

Clues about the timing of reionization and the nature of the ionizing sources responsible are imprinted in the ionization and thermal state of the IGM. In this thesis, I use high-resolution quasar spectra in conjunction with state-of-the-art hydrodynamical simulations to probe the IGM at high redshift, focusing on the ionization and thermal state of the gas. After reionization, the ionization state of the IGM is set by the intensity of the ultraviolet background(UVB), quantified by the hydrogen photoionization rate, Γ_bkg. At high redshifts this has been estimated by measuring the mean flux in the Lyα forest, and scaling Γ_bkg in simulations such that the simulated mean flux matches the observed value. In Chapter 3 I investigate whether the precision of these estimates can be improved by using the entire flux probability distribution function (PDF) instead of only the mean flux. Although I find it cannot improve the precision directly, the flux PDF can potentially be used to constrain other sources of error in observational estimates of Γ_bkg, and so may increase the precision indirectly. The ionizing output of a quasar will locally dominate over the UVB, and this leads to enhanced transmission bluewards of the quasar Lyα line, known as the proximity effect. In Chapter 4 I present the first measurements of Γ_bkg at z > 5 from the proximity effect. The UVB intensity declines smoothly with redshift over 4.6 < z < 6.4, implying a smooth evolution in the mean free path of ionizing photons. This suggests that reionization ends at z > 6.4. There is a drop in Γ_bkg by roughly a factor of five, which corresponds to a drop in the ionizing emissivity by about a factor of two. Such a redshift evolution in the emissivity cannot continue to much higher redshift without reionization failing to complete, which suggests that reionization cannot have ended much higher than z = 6.4. Estimates of Γ_bkg from the proximity effect and the mean flux are generally discrepant at z ~ 2-4, with those from the proximity effect systematically higher. This is generally attributed to effects of the quasar environment. I investigate the significance of several environmental biases on proximity effect measurements at z ~ 5-6 in Chapter 5. The biases are found to be small, and so the proximity effect is expected to give relatively unbiased estimates of Γ_bkg at z > 5, in contrast to lower redshifts. Photoionization heats the gas in the IGM, and so the thermal history of the IGM provides important constraints on reionization. The thermal state of the IGM is reflected in the level of small-scale structure in the Lyα forest. In Chapter 6 I quantify the small-scale structure using two independent statistics, the curvature and the peakiness, and convert these into a temperature by comparing with simulations. These are the first measurements of the temperature in the general IGM at z > 5. Both statistics show an increase in the temperature by a factor of roughly two from z = 4.4 to 5.6. This rise is sensitive, however, to any smoothing of the gas density distribution due to the thermal history spanning reionization. I find that this should only be a small effect, as otherwise the corrected temperatures at z ~ 4-5 are implausibly low. The temperature evolution therefore suggests a late reionization. The temperatures at z ≥ 4.8 are well fit by an adiabatic cooling curve, for which reasonable peak temperatures at the end of reionization are reached at 6 ≲ z ≲ 7. The temperatures at z ~ 4-5 are consistent with reionization being carried out by Pop II stars. In conclusion, the ionization and thermal state of the IGM at z ~ 5-6 suggest a late hydrogen reionization, driven by star-forming galaxies and ending around 6.5 ≲ z ≲ 7. This is consistent with other recent lines of observational evidence, and supports theoretical models that infer a late reionization from the observed star formation rate history.

L'âge des galaxies est un paramètre crucial dans le cadre des modèles de formation et d'évolution des galaxies. Ma thèse se base sur l'étude de cette quantité physique dans le cadre du sondage profond de VIMOS (VUDS). Ce sondage permet d'étudier les galaxies dans l'univers jeune et de remonter au moment où il était agé de seulement quelques centaines de millions d'années. Durant ce doctorat, j'ai pu prendre part au traitement des données de ce sondage et j'ai été responsable de l'ensemble de la correction des spectres du sondage. J'ai également modifié et amélioré le logiciel GOSSIP qui est un logiciel d'ajustement de modèle de galaxie permettant d'extraire les paramètres physiques des galaxies. L'utilisation de ce logiciel m'a permis d'étudier l'extinction par le milieu intergalactique des galaxies ainsi que leurs âges. Ceci m'a permis d'étudier l'époque de formation des galaxies ainsi que l'évolution du paramètre de Hubble. / Age of galaxie is a crucial parameter in the framework of galaxy formation and evolution. This thesis is based on the study of this parameter in the framework of the VIMOS Ultra Deep Survey. This galaxy survey allows to study galaxies when the universe was young and to go back when it was few hundreads of million years old. During this PhD I could take part of the data processing and I was responsible of all the spectroscopic corrections. I also implemented and improved the GOSSIP software. This software is a template fitting program that allows the extraction of galaxy physical parameters. The use of this software allowed me to study the extinction of the Inter Galactic medium (IGM) as well as their ages. I could then study the epoch of galaxy formation and the evolution of the Hubble parameter

abstract: A key open problem within galaxy evolution is to understand the evolution of galaxies towards quiescence. This work investigates the suppression of star-formation through shocks and turbulence at low-redshift, and at higher-redshifts, this work investigates the use of features within quiescent galaxy spectra to redshift estimation, and passive evolution of aging stellar populations to understand their star-formation histories. At low-$z$, this work focuses on the analysis of optical integral field spectroscopy data of a nearby ($z\sim0.0145$) unusual merging system, called the Taffy system because of radio emission that stretches between the two galaxies. This system, although a recent major-merger of gas-rich spirals, exhibits an atypically low star-formation rate and infrared luminosity. Strong evidence of shock heating as a mechanism for these atypical properties is presented. This result (in conjunction with many others) from the nearby Universe provides evidence for shocks and turbulence, perhaps due to mergers, as an effective feedback mechanism for the suppression of star-formation. At intermediate and higher-$z$, this work focuses on the analysis of Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) G800L grism spectroscopy and photometry of galaxies with a discernible 4000\AA\ break. The usefulness of 4000\AA/Balmer breaks as redshift indicators by comparing photometric, grism, and spectrophotometric redshifts (SPZs) to ground-based spectroscopic redshifts, is quantified. A spectral energy distribution (SED) fitting pipeline that is optimized for combined HST grism and photometric data, developed for this project, is presented. This pipeline is a template-fitting based routine which accounts for correlated data between neighboring points within grism spectra via the covariance matrix formalism, and also accounts for galaxy morphology along the dispersion direction. Evidence is provided showing that SPZs typically improve the accuracy of photometric redshifts by $\sim$17--60\%. For future space-based observatories like the Nancy Grace Roman Space Telescope (formerly the Wide Field InfraRed Survey Telescope, i.e., WFIRST) and Euclid, this work predicts $\sim$700--4400 galaxies\,degree$^{-2}$, within $1.6 \lesssim z \lesssim 3.4$, for galaxies with 4000\AA\ breaks and continuum-based redshifts accurate to $\lesssim$2\%. This work also investigates the star-formation histories of massive galaxies ($\mathrm{M_s \geq 10^{10.5}\, M_\odot}$). This is done through the analysis of the strength of the Magnesium absorption feature, Mgb, at $\sim$5175\AA. This analysis is carried out on stacks of HST ACS G800L grism data, stacked for galaxies binned on a color vs stellar mass plane. / Dissertation/Thesis / Doctoral Dissertation Astrophysics and Astronomy 2020

La découverte d'une population de galaxies submillimétrique (SMG) obscurcies par la poussière à grand décalage spectral, à l'aide de caméras submm, a révolutionné notre connaissance de l'évolution des galaxies et de la formation stellaire dans les conditions physiques extrêmes. Elles sont les flambées de formation stellaire les plus intenses dans l'Univers, approchant la limite d'Eddington et sont considérées comme les progéniteurs des galaxies actuelles les plus massives. Les modèles théoriques d'évolution de galaxies ont été remis en question par la découverte d'un grand nombre de SMGs à grand décalage spectral. Quelques unes sont fortement lentillées gravitationnelement par une galaxie. Les grands relevés extragalactiges récemment effectués en ont découvert plusieurs centaines, ouvrant de nouvelles opportunités pour observer le milieu interstellaire dans ces objets exceptionnels.Nous avons donc sélectionné un échantillon de SMG fortement lentillées à l'aide des densités de flux submm du relevé Herschel-ATLAS. À l'aide des télescopes de l'IRAM, nous avons construit un échantillon de 16 SMG détectés par la raie de l'eau. Nous avons trouvé une corrélation linéaire forte entre les luminosité d'H2O et infrarouge totale. Cela indique le rôle important du pompage IR lointain dans l'excitation des raies de l'eau. En utilisant un modèle de pompage IR lointain, nous avons obtenus les propriétés physiques du gaz et de la poussière. Nous avons montré que l'eau trace un gaz chaud et dense qui peut être étroitement lié à la formation des étoiles. Plusieurs raies d'H2O+ ont également été détectées dans trois SMG, montrant une corrélation étroite entre les luminosités des raies de H₂ O/H₂ O+ des ULIRG locales aux SMG. Le rapport de flux H2O+/H2O suggère que les rayons cosmiques provenant des activités fortes de formation stellaire sont probablement à l'origine de la chimie de l'oxygène.Nous avons observé de multiples transitions de CO dans chacune de nos SMG. Nous avons mis en évidence un effet significatif de lentillage différentiel qui peut entraîner une sous-estimation de la largeur de raie d'un facteur ~2. A l'aide d'une modélisation de type LVG et en utilisant une approche bayésienne, nous avons estimé la densité et la température du gaz, ainsi que sa densité de colonne. Nous avons ensuite mis en évidence une corrélation entre la pression thermique du gaz et l'efficacité de la formation stellaire. Nous avons également étudié les propriétés globales du gaz moléculaire et sa relation avec la formation d'étoiles ainsi que le rapport masse de gaz sur poussière et le temps d'épuisement du gaz. La détections de raies de carbone atomique dans ces SMG a étendu la corrélation linéaire locale entre luminosité des raies de CO/CI. Enfin, nous avons comparé les largeurs de raie de CO/H₂ O et constaté qu'elles étaient en bon accord. Cela suggère que les régions émettrices soient co-spatiale.Afin de comprendre les propriétés des émissions moléculaires dans ces sources, et plus généralement, leur structure et leur propriétés dynamiques, il est crucial d'acquérir des images à haute résolution angulaire. Nous avons donc observé deux sources avec ALMA/NOEMA en configuration étendue. Ces données nous permettent de reconstituer la morphologie intrinsèque de la source. Les émissions de poussière froide ont une plus petite taille en comparaison avec le gaz CO/H2 O, tandis que les deux derniers sont de taille similaire. En ajustant le modèle dynamique aux données CO, nous avons montré que ces galaxies peuvent être modélisée avec un disque en rotation, duquel nous avons pu déduire leurs masses dynamiques projetées et leurs rayons effectifs.Avec le futur NOEMA/ALMA, nous pourrons étendre ce genre d'observations à un plus grand nombre de SMG fortement amplifiées et même à des SMG non lentillées, afin d'étudier divers traceurs du gaz moléculaire et de comprendre les conditions physiques du milieux interstellaire et leur relation avec la formation des étoiles. / The discovery of a population of high-redshift dust-obscured submillimeter galaxies (SMGs) from ground-based submm cameras has revolutionised our understanding of galaxy evolution and star formation in extreme conditions. They are the strongest starbursts in the Universe approaching the Eddington limit and are believed to be the progenitors of the most massive galaxies today. However, theoretical models of galaxy evolution have even been challenged by a large number of detections of high-redshift high-redshift SMGs. A very few among them are gravitationally lensed by an intervening galaxy. Recent wide-area extragalactic surveys have discovered hundreds of such strongly lensed SMGs, opening new exciting opportunities for observing the interstellar medium in these exceptional objects.We have thus carefully selected a sample of strongly gravitational lensed SMGs based on the submm flux limit from the Herschel-ATLAS sample. Using IRAM telescopes, we have built a rich H₂ O-line-detected sample of 16 SMGs. We found a close-to-linear tight correlation between the H2O line and total infrared luminosity. This indicates the importance of far-IR pumping to the excitation of the H2O lines. Using a far-IR pumping model, we have derived the physical properties of the H2O gas and the dust. We showed that H2O lines trace a warm dense gas that may be closely related to the active star formation. Along with the H2O lines, several H2O+ lines have also been detected in three of our SMGs. We also find a tight correlation between the luminosity of the lines of H2O and H2O+ from local ULIRGs to high-redshift SMGs. The flux ratio between H2O+ and H2O suggests that cosmic rays from strong star forming activities are possibly driving the related oxygen chemistry.Another important common molecular gas tracer is the CO line. We have observed multiple transitions of the CO lines in each of our SMGs with IRAM30m telescope. By analysing the CO line profile, we discovered a significant differential lensing effect that might cause underestimation of the linewidth by a factor of ~2. Using LVG modelling and fitting the multi-J CO fluxes via a Bayesian approach, we derived gas densities and temperature, and CO column density per unit velocity gradient. We then found a correlation between the gas thermal pressure and the star formation efficiency. We have also studied the global properties of the molecular gas and its relationship with star formation. We have derived the gas to dust mass ratio and the gas depletion time, they show no difference compared with other SMGs. With the detections of atomic carbon lines in our SMGs, we extended the local linear correlation between the CO and CI line luminosity. Finally, we compared the linewidths of the CO and H2O emission line, which agree very well with each other. This suggests that the emitting regions of these two molecules are likely to be co-spatially located.In order to understand the properties of molecular emission in high-redshift SMGs, and more generally, the structure and the dynamical properties of these galaxies, it is crucial to acquire high-resolution images. We thus observed two of our brightest source with ALMA and NOEMA interferometers using their high spatial resolution configuration. These images have allowed us to reconstruct the intrinsic morphology of the sources. We compared the CO, H2O and dust emission. The cold dust emission has a smaller size compared with the CO and H2O gas, while the latter two are similar in size. By fitting the dynamical model to the CO data of the source, we have shown that the source can be modelled with a rotating disk. We derived the projected dynamical mass and the effective radius of those sources.With the future NOEMA and ALMA, we will be able to extend such kind of observations to a larger sample lensed SMGs and even to unlensed SMGs, to study various gas tracers, and to understand the physical conditions of the ISM and their relation to the star formation.