Дисертації: "Galaxies : à haute redshift"

1

Pham, Tuan Anh. "Observations millimétriques-submillimétriques de galaxies lentillées gravitationellement à haut redshift." Toulouse 3, 2014. http://thesesups.ups-tlse.fr/2709/.

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Nous présentons une étude détaillée d'observations faites de la galaxie hôte d'un quasar lointain (z~2. 8), RX J0911. La détection de l'émission des molécules CO a été possible grâce au lentillage gravitationnel dû à la présence d'une galaxie plus proche sur la ligne de vue et à la qualité de l'interféromètre du Plateau de Bure. On a obtenu de très bonnes résolutions tant en fréquence, permettant une mesure précise de la largeur de raie, qu'en direction, permettant de résoudre la source aussi bien sur la raie que dans le continu, donc à la fois pour le gaz et pour la poussière. Nous avons discuté en détail le mécanisme de lentillage gravitationnel. Comme souvent lorsqu'il s'agit de grandissements importants, la source est proche de la caustique de la lentille, dans le cas précis elle la chevauche. Il en résulte une dépendance importante du grandissement sur la position précise des sources ponctuelles à l'intérieur de la galaxie, donc des grandissements différents pour le gaz, la poussière et le quasar. D'autre part, les images sont non seulement aggrandies mais aussi déformées. Les données illustrent les avantages offerts par le lentillage en termes de sensibilité en même temps que les complications de l'analyse qui en découlent, source d'incertitudes sur les mesures. La raie CO(7-6) sort clairement du continu, permettant des mesures fiables des luminositées associées au gaz et à la poussière. Des études détaillées des quatre images ont permis de résoudre la source tant sur la raie que dans le continu, avec des rayons de 106±15 et 39±18 mas respectivement. Dans le cas de la raie, la qualité des données a permis de mettre en évidence une excentricité à 3. 3 déviations standard et un gradient de vitesse à 4. 5 déviations standards. La largeur très étroite de la raie implique une masse dynamique basse et les évaluations faites des masses de gaz et de poussière sont elles aussi très au dessous de ce qu'on mesure généralement pour des quasars à fort décalage vers le rouge. La valeur élevée de l'efficacité de formation d'étoiles situe la galaxie dans la partie haute de la distribution des galaxies, qu'elles soient à haut ou bas z: une fraction importante du volume gazeux semble avoir été épuisée à la suite d'une période de formation d'étoiles intense, laissant la galaxie à la frontière des galaxies hôtes de quasar à haut et bas z
The thesis gives a detailed account of observations of the host galaxy of a distant quasar, RX J0911. Detailed observations of the CO emission have been made possible thanks to the gravitational lensing offered by the presence of a galaxy in the foreground and to the quality of the Plateau de Bure Interferometer. High resolutions have been obtained both in frequency, allowing for a precise measurement of the line width, and in space, allowing for resolving spatially the source both on the line and in the continuum, namely both in its dust and gas content. The mechanism of gravitational lensing has been discussed in detail. As is often the case with large magnifications, the source happens to be in the vicinity of the lens caustic, in fact to overlap it. A consequence is a strong dependence of the magnification on the precise position of point sources in the galaxy, resulting in significantly different magnifications for the gas, the dust and the central QSO. Moreover, the morphology of the observed images is distorted in addition to being amplified. The data illustrate the advantage offered by the strong lensing in terms of increased sensitivity as well as the complication that results, causing an additional source of uncertainties on the quantities that are accessible to measurement. The CO(7-6) line stands out clearly above continuum, allowing for reliable measurements of the gas and dust luminosities. Detailed studies of the four lensed images have made it possible to resolve the source in both the line and the continuum with rms radii of 106±15 and 39±18 mas respectively. In the line case, the quality of the data have provided evidence for an ellipticity of the source, 3. 3 standard deviations away from circular, and for a velocity gradient correlated with the source ellipticity, at the level of 4. 5 standard deviations. The very narrow CO(7-6) line implies a low dynamical mass and both gas and dust mass evaluations fall on the low side of the normal high-z quasar host population. The large star formation efficiency is on the high side of both low-z and high-z galaxies: much of the gas has been exhausted after an intense star formation period, leaving the galaxy at the border between high-z and low-z quasar hosts

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2

Zanella, Anita. "Structural properties of clumpy galaxies and spheroids at high redshift." Thesis, Sorbonne Paris Cité, 2016. http://www.theses.fr/2016USPCC314/document.

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Cette thèse explore la question ouverte des mécanismes selon lesquels les galaxies lointaines évoluent au cours du temps. Elle se concentre sur l’étude des galaxies irrégulières et sur la cause de l’évolution en taille des galaxies passives et compactes. Bien que des régions de formation stellaire très lumineuses (clumps) soient observées dans les galaxies irrégulières depuis longtemps, leur nature et évolution sont encore débattues. Les instabilités gravitationnelles des disques ont été proposées comme la cause principale pour la formation in-situ des clumps, même si certains d’entre eux pourraient avoir une origine ex-situ. De plus, il n’est pas encore clair s’ils peuvent vivre longtemps ou si les vents stellaires les détruisent rapidement. À partir de l’étude détaillée d’un clump très jeune que nous avons découvert dans le disque d’une galaxie à redshift z~2 et de l’analyse d’un échantillon statistique, j’ai conclu que les clumps peuvent se former in-situ et qu’ils vivent typiquement 500 Myr. Ce résultat conforte les simulations numériques qui indiquent que les clumps ont un rôle important pour la croissance de leur noyau. Cela pourrait stabiliser le disque et y avoir un lien avec la formation des galaxies compactes et passives qui ont été decouvertes à haut redshift. Elles ont des tailles significativement plus petites, à masse égale, que celles de leurs homologues locales. Cette découverte a déclenché un débat concernant les possibles mécanismes qui peuvent augmenter leur taille sans altérer leur masse. J’ai analysé un échantillon de 32 galaxies et j’ai conclu que des multiples fusions mineures pourraient être les responsables principaux de leur evolution temporelle
This thesis explores the still unanswered question of how distant galaxies evolve through cosmic time: on one side it focuses on star-forming clumpy galaxies, on the other it investigates the size evolution of passive compact ones. Despite star forming clumps have been observed in high-redshift irregular galaxies since a while, their nature and fate are still highly debated. Violent gravitational disk instability in gas-rich, turbulent galaxies has been proposed as the main cause for in-situ clumps formation, although a fraction of them might have an ex-situ origin. Furthermore, clumps contribution to galaxy evolution is highly debated: it is not clear yet if they are long-lived or if stellar feedback rapidly disrupts them. From both the in-depth study of an extremely young clump that we discovered in the disk of a galaxy at redshift z ~ 2, and the analysis of a full statistical sample, I concluded that at least some clumps form in-situ due to violent disk instability and that they typically live ~ 500 Myr. This supports numerical simulations indicating that clumps are longlived and could play an important role in bulge growth. This might stabilize the disk, quench star formation and have therefore a link with the formation of the compact and passive galaxies that have been observed at high redshift. They have significant smaller sizes, at fixed stellar mass, than local counterparts. This discovery has ignited an important debate concerning the possible mechanisms that could inflate the galaxy sizes without altering much their mass. I analyzed a sample of 32 galaxies and I concluded that multiple minor mergers could be the main drivers of their observed time evolution

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3

Salmi, Fadia. "Comprendre les modes de formation d’étoiles dans l’univers lointain." Thesis, Paris 11, 2012. http://www.theses.fr/2012PA112173/document.

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L'objectif de mon travail de thèse a consisté à tenter de comprendre quels sont les mécanismes principaux à l'origine de la formation d'étoiles dans les galaxies au cours des derniers dix milliards d'années. Alors qu'il avait été proposé dans le passé que le rôle des fusions de galaxies était dominant pour expliquer l'allumage de la formation d'étoiles dans les galaxies lointaines formant leurs étoiles à de très grands taux, des études plus récentes ont au contraire mis en évidence des lois d'échelles reliant le taux de formation d'étoiles des galaxies à leur masse stellaire ou masse de gaz. La faible dispersion de ces lois semblait être en contradiction avec l'idée d'épisodes stochastiques violents de formation stellaire liés à des interactions, mais plutôt en accord avec une nouvelle vision de l'histoire des galaxies où celles-ci sont nourries de manière continue en gaz intergalactique.Nous nous sommes particulièrement intéressés à l'une de ces lois d'échelles, la relation entre le taux de formation d'étoiles (SFR) et la masse stellaire des galaxies, appelées communément la séquence principale des galaxies à formation d'étoiles. Nous avons étudié cette séquence principale, SFR-M*, en fonction de la morphologie et d'autres paramètres physiques comme le rayon, la couleur, la clumpiness. Le but étant de comprendre l'origine de la dispersion de cette relation en lien avec les processus physiques responsables de cette séquence afin d'identifier le mode principal de formation d'étoile gouvernant cette séquence. Ce travail a nécessité une approche multi-longueurs d'ondes ainsi que l'utilisation de simulations de profils de galaxies pour distinguer les différents types morphologiques de galaxies impliqués dans la séquence principale
The goal of my PhD study consists at attempt to understand what are the main processes at the origin of the star formation in the galaxies over the last 10 billions years. While it was proposed in the past that merging of galaxies has a dominant role to explain the triggering of the star formation in the distant galaxies having high star formation rates, in the opposite, more recent studies revealed scaling laws linking the star formation rate in the galaxies to their stellar mass or their gas mass. The small dispersion of these laws seems to be in contradiction with the idea of powerful stochastic events due to interactions, but rather in agreement with the new vision of galaxy history where the latter are continuously fed by intergalactic gas. We were especially interested in one of this scaling law, the relation between the star formation (SFR) and the stellar mass (M*) of galaxies, commonly called the main sequence of star forming galaxies. We studied this main sequence, SFR-M*, in function of the morphology and other physical parameters like the radius, the colour, the clumpiness. The goal was to understand the origin of the sequence’s dispersion related to the physical processes underlying this sequence in order to identify the main mode of star formation controlling this sequence. This work needed a multi-wavelength approach as well as the use of galaxies profile simulation to distinguish between the different galaxy morphological types implied in the main sequence

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4

Bieri, Rebekka. "The Role of AGN Feedback in Galaxy Formation." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066292/document.

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L’objectif de ma thèse porte sur les interactions entre les noyaux actifs de galaxies et le milieu interstellaire des galaxies. En particulier, je mets l’accent sur les deux mécanismes possibles responsables de la production des vents par les trous noirs : les jets et les vents produits par le rayonnement de ces trous noirs. Les simulations hydrodynamiques de haute résolution des galaxies comprenant la rétroac- tion d’un jet ont montré que l’activité des noyaux actifs peut conduire à une pression exces- sive sur les régions denses de formation stellaire dans les galaxies, et donc à augmenter la formation d’étoiles, conduisant à un effet positif de rétroaction. Je montre que ces noyaux actifs induits par pression régulée et formation d’étoiles peuvent aussi être une explica- tion possible des taux de formation stellaire élevés observés dans l’Univers à haut décalage spectral. De plus, j’ai également étudié en détails comment le rayonnement émis à partir d’un disque d’accrétion autour du trou noir agit efficacement avec le milieu interstellaire et entraîne un fort vent galactique, en simulant la propagation des photons à partir des équations hydrodynamiques du rayonnement. Les simulations montrent que la grande luminosité d’un quasar est en effet capable de conduire des vents à grande échelle et à grande vitesse. Le rayonnement infrarouge est nécessaire pour transérer efficacement le gaz par multi-diffusion sur la poussière dans les nuages denses. Le nombre typique de multi-diffusion diminue rapidement quand le nuage central de gaz central se dilate et se rompt, ce qui permet au rayonnement de s’échapper à travers les canaux à faible densité
Supermassive black holes (SMBHs) are known to reside in the centres of most large galaxies. The masses of these SMBHs are known to correlate with large-scale properties of the host galaxy suggesting that the growth of the BHs and large-scale structures are tightly linked. A natural explanation for the observed correlation is to invoke a self-regulated mechanism involving feedback from Active Galactic Nuclei (AGN). The focus of this thesis is on the interactions between AGN outflows and the ISM and how the feedback impacts the host galaxy. In particular, it focuses on the two possible mechanism of outflows, namely, outflows related to AGN jets and outflows produced by AGN radiation. High resolution, galaxy scale hydrodynamical simulations of jet-driven feedback have shown that AGN activity can over-pressurise dense star-formation regions of galaxies and thus enhance star formation, leading to a positive feedback effect. I propose, that such AGN-induced pressure-regulated star formation may also be a possible explanation of the high star formation rates recently found in the high-redshift Universe. In order to study in more detail the effects of over-pressurisation of the galaxy, I have performed a large set of isolated disc simulations with varying gas-richness in the galaxy. I found that even moderate levels of over-pressurisation of the galaxy boosts the global star formation rate by an order of magnitude. Additionally, stable discs turn unstable which leads to significant fragmentation of the gas content of the galaxy, similar to what is observed in high-redshift galaxies. The observed increase in the star formation rate of the galaxy is in line with theoretical predictions. I have also studied in detail how radiation emitted from a thin accretion disc surrounding the BH effectively couples to the surrounding ISM and drives a large scale wind. Quasar activity is typically triggered by extreme episodes of gas accretion onto the SMBH, in particular in high-redshift galaxies. The photons emitted by a quasar eventually couple to the gas and drive large scale winds. In most hydrodynamical simulations, quasar feedback is approximated as a local thermal energy deposit within a few resolution elements, where the efficiency of the coupling between radiation of the gas is represented by a single parameter tuned to match global observations. In reality, this parameter conceals various physical processes that are not yet fully un- derstood as they rely on a number of assumptions about, for instance, the absorption of photons, mean free paths, optical depths, and shielding. To study the coupling between the photons and the gas I simulated the photon propagation using radiation-hydrodynamical equations (RHD), which describe the emission, absorption and propagation of photons with the gas and dust. Such an approach is critical for a better understanding of the coupling between the radiation and gas and how hydrodynamical sub-grid models can be improved in light of these results

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5

Villa, Vélez Jorge Andrés. "Spectrophotometric analysis around cosmic noon : emission-lines, dust attenuation, and star formation." Thesis, Aix-Marseille, 2021. http://www.theses.fr/2021AIXM0440.

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Les galaxies sont les éléments constitutifs de l'Univers. La compréhension de leur rôle dans le cosmos se fait grâce à l’étude de la lumière qu’elles émettent d'un point de vue multi-longueur d'onde car les processus physiques en leur sein sont responsables du rayonnement que nous observons. Dans ce travail, un échantillon de galaxies dans le champ COSMOS avec une photométrie de l'ultraviolet à l'infrarouge lointain et des flux Ha, Hb, [OIII]5007 est étudié à l'aide du logiciel CIGALE. La photométrie est ajustée avec les flux Ha pour obtenir des estimations robustes de la masse stellaire, du taux de formation d'étoiles (SFR) et de l'atténuation dans les raies d'émission. Grâce à la correction par la poussière nous avons proposé une correction de la relation liant le SFR et la luminosité de [OIII]5007. La dispersion de cette relation est étudiée en fonction des propriétés du milieu interstellaire comme le paramètre d'ionisation et la métallicité du gaz en ajustant la photométrie et les flux Ha, Hb, [OIII]5007. Les modèles d'émission nébulaire dans CIGALE sont mis à jour pour reproduire l'émission nébulaire de ces galaxies à z~1.6. Ces modèles sont également utilisés pour créer des catalogues de spectres fictifs pour la collaboration MOONS. Un sous-échantillon de galaxies dans le champ COSMOS est ajusté en couvrant la photométrie de l'ultraviolet à l'infrarouge moyen. Des spectres fictifs sont créés, incluant soit le continuum stellaire soit le continuum stellaire et l'émission nébulaire. L'utilité de l'inclusion des informations spectroscopiques en plus de la photométrie dans l'ajustement SED est présenté dans ce travail en préparation des futurs relevés spectroscopiques
Galaxies are the building blocks of the Universe. Understanding their role in the cosmos translates into studying their emitted light from a multi-wavelength perspective as a large variety of physical processes inside them are responsible for the radiation we observe. In this work, a sample of galaxies in the COSMOS field with ultraviolet to far-infrared photometry and Ha, Hb, [OIII]5007 fluxes is studied using spectral energy distribution (SED) fitting software CIGALE. The photometry is firstly fitted along with the Ha fluxes to derive robust estimations of the stellar mass, star formation rate (SFR), and attenuation in the emission lines. A dust-corrected relation between SFR and [OIII]5007 luminosity is proposed. The dispersion in this relation is studied under the light of the interstellar medium (ISM) properties as the ionization parameter and gas-phase metallicity fitting the photometry and the Ha, Hb, [OIII]5007 fluxes. The nebular emission models inside CIGALE are updated to reproduce the nebular emission of these galaxies at z~1.6. These models are also used to create mock spectra catalogs for the Multi-Object Optical and Near-infrared Spectrograph (MOONS) collaboration. A sub-sample of galaxies in the COSMOS field is fitted covering ultraviolet to mid-infrared photometry. Mock spectra are created including either stellar continuum-only or stellar continuum and nebular emission. The power of including spectroscopic information along with the photometry in the SED fitting process is presented in this work in preparation for future large spectroscopic surveys that will open a new era in galactic and extragalactic astronomy

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6

Roos, Orianne. "Modelling feedback processes, star formation and outflows in high-redshift galaxies." Thesis, Sorbonne Paris Cité, 2016. http://www.theses.fr/2016USPCC148/document.

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Dans l’Univers, on observe des galaxies lointaines ne formant plus d’étoiles, mais les astrophysiciens n’ont pas encore identifié avec certitude les phénomènes physiques à l’origine de leur “mort”. Pour apporter des éléments de réponse, je me suis penchée sur l’étude de phénomènes qui pourraient y jouer un rôle : les processus de rétroaction des étoiles et des trous noirs supermassifs actifs, la formation stellaire, et les vents galactiques. Le Chapitre 1 présente toutes les notions nécessaires à la compréhension du problème : les caractéristiques des galaxies typiques de l’Univers proche et lointain ; les vents galactiques ; la mort des galaxies; les trous noirs supermassifs actifs (noyaux actifs de galaxies, AGN) et les étoiles ; et leur rétroaction. Dans le Chapitre 2, je présente les techniques numériques utilisées : le code de simulations astrophysiques RAMSES et le code de transfert radiatif Cloudy, que j’ai utilisé pour développer une méthode de calcul de l’état d’ionisation d’une galaxie, détaillée au Chapitre 3. Le Chapitre 4 étudie le couplage entre les trous noirs actifs et les étoiles, avec le projet POGO, Origines Physiques des Vents Galactiques. Durant cette thèse, j’ai montré que les trous noirs actifs n’étaient pas en mesure de tuer subitement leur hôte, même en prenant en compte la rétroaction des étoiles, et que leur couplage peut réduire ou renforcer les vents dans les galaxies en fonction de leur masse. Le Chapitre 5 fait un état de l’art du domaine avant et pendant mon doctorat, reprend les conclusions de cette thèse et donne quelques perspectives, notamment en ce qui concerne le rôle additionnel des rayons cosmiques dans la mort des galaxies
In the Universe, we observe galaxies forming no, or almost no, stars anymore, but astrophysicists do not know yet what physical mechanisms cause their “death”. To give clues to solve the problem, I studied feedback processes from stars and active supermassive black holes, star formation and galactic outflows. Chapter 1 presents all the notions to understand the problem: the characteristics of typical galaxies in the local and distant Universe, galactic outflows, galaxy death, active supermassive black holes, stars, and their feedback processes. In Chapter 2, I describe the numerical techniques I used: the simulation code RAMSES, and the radiative transfer code Cloudy, which I used to develop a computation method to get the ionization state of an entire galaxy. This method is presented in Chapter 3. Chapter 4 studies the coupling between the feedback processes of active supermassive black holes and stars, with the POGO project, Physical Origins of Galactic Outflows. During this thesis, I showed that typical active supermassive black hole cannot suddenly kill their host, even when stellar feedback processes are accounted for, and that their coupling either reduces or enhances the mass outflow rate depending on the mass of the host. In Chapter 5, I give a state-of-the-art about active supermassive black holes before and during my thesis, sum up the conclusions of the work, and give perspectives to enlarge the scope of the study, especially regarding the additional role of cosmic rays in the death of galaxies

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7

Yang, Chentao. "Physical conditions of the interstellar medium in high-redshift submillimetre bright galaxies." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS361/document.

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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

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Fensch, Jérémy. "Star and stellar cluster formation in gas-dominated galaxies." Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCC207/document.

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Nous étudions la formation d’étoiles et d’amas d’étoiles dans les galaxies dominées par le gaz. Ce terme réfère en premier lieu aux galaxies de l’époque du pic de formation d’étoiles dans l’histoire de l’Univers, qui s’est déroulé vers z ~ 2, mais aussi à leurs analogues locaux, les galaxies naines de marées. En premier lieu, en utilisant des simulations numériques, nous montrons que les galaxies massives typiques de z=2, avec une fraction de gaz d’environ 50%, forment des structures gazeuses massives (10**7-8 masses solaires) et liées gravitationnellement, appelées grumeaux dans la suite. Ces grumeaux ne se forment dans des galaxies avec une fraction de gaz inférieure à 25%. Nous présentons ensuite une étude observationnelle d’un analogue local de grumeaux de galaxies à z=2, la galaxie naine de marée NGC 5291N. Une analyse des raies d’émission de cette galaxie montre la présence de chocs sur les pourtours de l’objet. La photométrie des amas d’étoiles de cette galaxie montre que les amas les plus jeunes (< 10 millions d’années) sont significativement moins massifs que les amas plus âgés. Ceci peut être le signe de fusions progressives d’amas et/ou d’une forte activité de formation stellaire dans ce système il y a environ 500 millions d’années.Dans un second lieu nous étudions comment la fraction de gaz influe sur la formation d’étoiles et d’amas stellaires dans des fusions de galaxies à z=2. En utilisant des simulations numériques nous montrons que ces fusions n’augmentent que relativement peu le taux de formation d’étoiles et d’amas stellaires comparativement aux fusions de galaxies locales, à faible fraction de gaz. Nous montrons que ceci est due à une saturation de plusieurs facteurs physiques, qui sont déjà présents naturellement dans les galaxies isolées à z=2 et sont donc comparativement peu accentués par les fusions. Il s’agit de la turbulence du gaz, des zones de champ de marée compressif et des flux de matières vers le noyau de la galaxie. Nous montrons aussi que les structures stellaires formées au sein des grumeaux de gaz sont préservées par la fusion : elles sont éjectées des disques et orbitent dans le halo de la galaxie résultante de la fusion, où elles peuvent devenir les progéniteurs de certains amas globulaires
We study the formation of stars and stellar clusters in gas-dominated galaxies. This term primarily refers to galaxies from the epoch of the peak of the cosmic star formation history, which occurred at z ~ 2, but also to their local analogues, the tidal dwarf galaxies.Firstly, using numerical simulations, we show that the massive galaxies at z = 2, which have a gas fraction of about 50%, form massive (10**7-8 solar masses) and gravitationally bound structures, which we call clumps thereafter. These clumps do not form in galaxies with a gas fraction below 25%. We then present an observational study of a local analogue of a z = 2 galactic clump, which is the tidal dwarf galaxy NGC 5291N. The analysis of emission lines show the presence of shocks on the outskirts of the object. Photometry of this galaxy’s stellar clusters show that the youngest clusters (< 10 million years) are significantly less massive than older clusters. This could be the sign of ongoing cluster mergers and/or of a strong star formation activity in this system about 500 million years ago).Secondly, we study how the gas fraction impacts the formation of stars and stellar clusters in galaxy mergers at z = 2. Using numerical simulations we show that these mergers only slightly increase the star and stellar cluster formation rate, compared to local galaxy mergers, which have a lower gas fraction. We show that this is due to the saturation of several physical quantities, which are already strong in isolated z=2 galaxies and are thus less enhanced by the merger. These factors are gas turbulence, compressive tides and nuclear gas inflows, We also show that the stellar structures formed in the gaseous clumps are preserved by the fusion: they are ejected from the disk and orbit in the halo of the remnant galaxy, where they may become the progenitors of some globular clusters

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9

Ribeiro, Bruno. "Morphology as a tracer of evolution in the early phases of galaxy assembly." Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4744/document.

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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
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

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10

Collet, Cédric. "Role of AGN feedback in galaxy evolution at high-redshift." Phd thesis, Université Paris Sud - Paris XI, 2014. http://tel.archives-ouvertes.fr/tel-01061155.

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There is growing evidence that supermassive black holes may play a crucial role for galaxy evolution, in particular during the formation of massive galaxies at high redshift (z ~ 2 - 3). Our work focuses on quantifying the effects of jets of radiogalaxies and of large bolometric luminosities of quasars on the interstellar gas in their host galaxies. To this end, we studied the kinematics of the ionized gas in 12 moderately powerful radio galaxies and 11 quasars (6 radio-loud and 5 radio-quiet) at high redshifts with rest-frame optical imaging spectroscopy obtained at the VLT with SINFONI. We searched for outflows and other signatures of feedback from the supermassive black holes in the centers of these galaxies to evaluate if the AGN may plausibly quench star formation. In our sample of moderately powerful radiogalaxies, we observe velocity dispersions nearly as large as those observed in the most powerful ones (with FWHM ~ 1000 km/s), but the quantity of ionized gas is decreased by one order of magnitude (Mion gas ~ 10^8 - 10^9 Msun) and velocity gradients tend to be less dramatic (Δv < 400 km/s), when they are observed. In our sample of quasars, we had to carefully subtract the broad spectral component of emission lines to have access to its narrow, and spatially extended, component. We detect truly extended emission line regions in 4/6 sources of our radio-loud subsample and in 1/5 source of our radio-quiet subsample. We estimate that masses of ionized gas in these sources are smaller than in our sample of high-redshift radiogalaxies (with Mion gas ~ 10^7 - 10^8 Msun) and kinematics tend to be more quiescent, akin to what is observed in local quasars. Finally, detailed observations of two outliers among our sample of high-redshift radiogalaxies revealed that one of them is closely surrounded by 14 companions galaxies, hence lying in an overdensity. We therefore interpret the presence and morphology of ionized gas around these galaxies as evidence for repeated cycles ouf AGN outbursts, akin to what can be observed in local clusters of galaxies, which are prime examples of AGN feedback in the nearby Universe.

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11

Guery, David. "Étude statistique des structures à grand redshift observées par les satellites Planck et Herschel." Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112162/document.

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Les modèles et les observations actuels de l’Univers sont en accords aux grandes échelles. Néanmoins, cela ne permet pas d’expliquer la formation des structures baryoniques dans l’Univers. Afin de contraindre la formation des structures dans l’Univers, des observations sont nécessaires à différents redshifts pour observer les structures à différentes étapes d’évolutions. Le satellite Planck donne accès à des objets dont les redshifts sont compris entre z=2 et z=4. Ainsi environ 1200 objets extragalactiques susceptibles d’être à haut redshift sont détectés dans 26% du ciel, autour des pôles galactiques. Un sous échantillon de 228 sources est observé à plus grande sensibilité et résolution angulaire avec le satellite Herschel. Grâce à ces observations je peux résoudre les sources ponctuelles de Planck en plusieurs sources Herschel. J’identifie alors trois possibilités de type de sources, soit c’est une candidate de source amplifiée par lentillage gravitationnel, soit c’est un candidat d’amas de galaxies à haut redshift, soit c’est un alignement de sources fortuit le long de la ligne de visé. Après analyse, j’ai identifié dans cet échantillon 11 sources amplifiées par lentillage gravitationnel parmi les plus brillantes du ciel sub-millimétrique. Ces sources ont des redshifts compris entre z=2.2 et z=3.6 (Canameras et al., 2015) et permettent de sonder la formation stellaire dans l’Univers lointain. Il reste 217 surdensités de sources que j’ai étudié. En utilisant la couleur des sources Herschel, j’ai calculé une estimation de la densité des sources. 50% des champs Herschel de l’échantillon on une surdensité supérieur à 10sigma lorsque l’on sélectionne les sources rouges (S250/S350 < 1.4 et S500/S350 > 0.6). Cela montre que l’échantillon est principalement composé de surdensité de source rouge. En ajustant un corps noir modifié à 35K sur les données photométrique Herschel-SPIRE je montre que la distribution de redshift photométrique des sources piquent à z=2. Notre échantillon se compose donc de 11 sources lentillées et 217 potentiels amas de galaxies à redshift z~2. Ces potentiels amas de galaxies se compose d’en moyenne 9 sources dans 4.5’ de diamètre. Les sources individuelles ont des luminosités infrarouges d’environ 4.1012 Lsol ce qui correspond d’après Bell et al. 2003 à un taux de formation stellaire (SFR) de 700 Msol.yr-1. Cela mène pour les potentielles structures à une luminosité de 4.1013 Msol et un SFR de 7000 Msol.yr-1. Notre échantillon trace donc les structures denses du ciel à fort taux de formation stellaire. Cet échantillon sera donc clé dans la compréhension de la formation des structures et des étoiles à des redshifts autour de z=2
Actual models and observations of the Universe agreed at large scale. But the formation of baryonic structures remains unknown. To constrain structure formation in the Universe, observatoins are needed at different redshift to see different evolution steps. Planck satellite gives an acces to objetcs in the redshift range z=2 to z=4. Thus we detect about 1200 extragalactic objects in 26% of the sky near galactic poles, candidates to be at high redshift. A sample of 228 sources is observed at higher sensibility and resolution than Planck with Herschel satellite. This lead to resolve ponctual Planck sources in several Herschel sources. So I identify three possible types of object : candidates sources of gravitationally amplified lenses, galaxy cluster candidates and alignement of sources along the line of sight. I find in the sample 11 sources amplified by gravitationnal lensing, some of the brightest of the submillimeter sky. Those have redshift between z=2.2 and z=3.6 (Canameras et al., 2015) and provide a zoom in the stellar formation of the far Universe. It let 217 overdensity of sources that I study. With their colour in Herschel data, I find an estimate of their density. 50% of Herschel fields have an overdensity greater than 10sigma using red sources colour selection (S250/S350 < 1.4 et S500/S350 > 0.6). This show that our ample is mainly composed of red overdensity. Fitting Herschel-SPIRE photometry with a modify black body at 35K, I show that the photmetric redshift distribution of Herschel sources peaks around z=2. Our sample is now composed of 11 lensed sources and 217 galaxy cluster candidates at z~2. These galaxy cluster candidates contain an average of 9 SPIRE sources in 4.5’ diameter beam. Individual sources have a luminosity distribution peaking at 4.1012 Lsun which leads to a star formation rate (SFR) of 700 Msun.yr-1 (Bell et al. 2003). This gives an estimate structure luminosity of 4.1013 Msun and an SFR of 7000 Msun.yr-1 assuming that sources are members of the same structure. Our sample traces dense structure at high star formation rate in the full sky. This sample will be a key in the comprehension of structure formation and star formation at redshift about z=2

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12

Salmi, Fadia. "Comprendre les modes de formation d'étoiles dans l'univers lointain." Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00790749.

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L'objectif de mon travail de thèse a consisté à tenter de comprendre quels sont les mécanismes principaux à l'origine de la formation d'étoiles dans les galaxies au cours des derniers dix milliards d'années. Alors qu'il avait été proposé dans le passé que le rôle des fusions de galaxies était dominant pour expliquer l'allumage de la formation d'étoiles dans les galaxies lointaines formant leurs étoiles à de très grands taux, des études plus récentes ont au contraire mis en évidence des lois d'échelles reliant le taux de formation d'étoiles des galaxies à leur masse stellaire ou masse de gaz. La faible dispersion de ces lois semblait être en contradiction avec l'idée d'épisodes stochastiques violents de formation stellaire liés à des interactions, mais plutôt en accord avec une nouvelle vision de l'histoire des galaxies où celles-ci sont nourries de manière continue en gaz intergalactique.Nous nous sommes particulièrement intéressés à l'une de ces lois d'échelles, la relation entre le taux de formation d'étoiles (SFR) et la masse stellaire des galaxies, appelées communément la séquence principale des galaxies à formation d'étoiles. Nous avons étudié cette séquence principale, SFR-M*, en fonction de la morphologie et d'autres paramètres physiques comme le rayon, la couleur, la clumpiness. Le but étant de comprendre l'origine de la dispersion de cette relation en lien avec les processus physiques responsables de cette séquence afin d'identifier le mode principal de formation d'étoile gouvernant cette séquence. Ce travail a nécessité une approche multi-longueurs d'ondes ainsi que l'utilisation de simulations de profils de galaxies pour distinguer les différents types morphologiques de galaxies impliqués dans la séquence principale.

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13

Plat, Adèle. "Modélisation et interprétation des propriétés spectrales des galaxies primordiales." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS298.

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Pendant le premier milliard d’années de l’Univers, les premières galaxies se sont formées et ont réionisé le milieu intergalactique. Grâce au James Webb Space Telescope, l’observation de spectres ultraviolets et optiques des galaxies de l’époque de la réionisation sera bientôt possible. L’émission de ces galaxies contient des informations précieuses sur leurs propriétés physiques et en particulier sur la caractérisation des sources à l’origine de la réionisation de l’Univers. Nous explorons des modèles physiquement auto consistants de galaxies à formation d’étoiles, en incluant l’émission du gaz interstellaire chauffé par de jeunes étoiles, la fuite des photons ionisants hors de la galaxie, l’émission d’un noyau actif de galaxie et de chocs radiatifs. Ces modèles sont comparés dans un ensemble de diagrammes impliquant des raies d’émission avec un échantillon de galaxies à formation d’étoiles de faible métallicité et de galaxies qui perdent des photons du continu de Lyman. Cette analyse nous renseigne sur les contraintes que l’on peut obtenir concernant la nature des sources de photons ionisants ainsi que la quantité de ces photons qui s’échappent dans le milieu intergalactique. Enfin, nous présentons également quelques tests préliminaires de l’implémentation en cours de l’émission des régions à raies étroites de noyaux actifs de galaxies dans un outil d’interprétation spectrale de galaxies
During the first billion years of the Universe, the first galaxies formed and ionized the neutral inter-galactic medium. Observations of rest-frame ultraviolet and optical spectra of galaxies into the reionization epoch will soon be possible with the help of the James Webb Space Telescope. The light emitted by these galaxies contains valuable information about their physical properties, in particular, the characterisation of the sources that were able to reionize the Universe. We explore physically self-consistent models of star-forming galaxies, including the influence of stellar multiplicity on the production of ionizing photons by young stellar populations, the leakage of Lyman-continuum photons from density-bounded HII regions and the contribution by an active galactic nucleus and radiative shocks to nebular emission. We compare these models with a sample of metal-poor star-forming galaxies – whose properties are expected to approach those of primeval galaxies – and Lyman-continuum leakers at various redshifts, in a collection of ultraviolet and optical emission-line diagnostic diagrams. From this analysis, we investigate how we can learn about the nature of the ionizing sources and the leakage of ionizing photons in such galaxies. We also present preliminary tests of the implementation in progress of the emission from narrow-line regions of active galactic nuclei in a spectral interpretation tool

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14

Riggucini, Laurie. "Caractériser la formation d'étoiles obscurcie à z ~ 2 dans l'Univers." Thesis, Paris 11, 2011. http://www.theses.fr/2011PA112186/document.

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Une fraction non négligeable de l'histoire de la formation stellaire a lieu dans des environnements très affectés par la poussière. Il est donc naturel de se demander si on arrive à bien contraindre cette activité de formation d'étoiles. En effet, une part importante de cette activité pourrait être manquée due à la présence de poussière. C'est dans ce contexte que s'inscrit le travail que je vais présenter.Dans la première partie de ma thèse, j'ai eu pour but de déterminer la fraction de galaxies lumineuses formant des étoiles à haut redshift (i.e. 1.5 1mJy) présentent des couleurs 100/24 et 160/24 plus faibles que les autres sources du champ COSMOS et leur luminosité semble donc provenir majoritairement d'un AGN. Les avancées technologiques et l'exploration des longueurs d'ondes en infra-rouge lointain et en submillimétrique, avec notamment Herschel, SCUBA-2, Alma, JWST, permettront de mieux comprendre la connexion AGN/ flambée de formation stellaire au sein des galaxies jusqu'à des hauts redshifts
A non-negligible fraction of the star formation across cosmic time occurred within dust-enshrouded environment. One question of the main interest is then do we really know the exact amount of star formation activity. Indeed, this amount could be strongly biased by the effect of dust extinction.This features the context of the work I will discuss here.First of all, I focused my work on determining the number of luminous star-forming galaxies at 1.5 1mJy) OFIR sources present fainter 100/24 and 160/24 colors than the rest of the 24μm-selected sources. Their luminosity might then come from a strong AGN activity. The forthcoming facilities that will operate at long wavelengths (e.g., JWST, AKMA, SCUBA-2, etc.) will allow a better understanding of the link between the AGN activity and the star-forming one, up to high redshifts

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15

Thomas, Romain. "Etude de l'âge des galaxies dans le sondage VUDS à 2." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4762.

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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

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16

Huertas, Marc. "Etude de la morphologie de galaxies lointaines à partir de grands relevés en imagerie infrarouge depuis le sol." Phd thesis, Observatoire de Paris, 2008. http://tel.archives-ouvertes.fr/tel-00349783.

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Dans l'Univers local, la distribution de galaxies est bimodale, reflétant la relation existante entre la couleur et la morphologie.
Une question clef en cosmologie observationnelle est de comprendre comment cette dichotomie est apparue au cours de l'histoire de l'Univers. Les relevés de galaxies ont pour but d'isoler des populations de galaxies à différentes époques cosmiques et de suivre leur évolution. Quantifier de manière fiable les morphologies de galaxies lointaines demeure cependant un obstacle majeur.
Dans le visible, les progrès durant les dix dernières années proviennent essentiellement de données acquises par le télescope spatial Hubble (HST) grâce à la haute résolution angulaire délivrée. Au delà de z~1 pourtant, les caméras visibles du HST sondent le flux UV des galaxies ce qui peut biaiser la morphologie estimée vers des types tardifs. De ce point de vue, les observations dans le proche infrarouge au delà de z~1 sont particulièrement importantes puisque la lumière analysée provient d'étoiles évoluées et est donc moins affectée par des épisodes récents de formation stellaire.
Dans cette thèse, on s'interroge sur la possibilité de quantifier les morphologies de galaxies lointaines dans l'infrarouge proche à l'aide de télescopes au sol afin de quantifier les effets de k-correction morphologique.
Dans un premier temps, l'utilisation d'optique adaptative pour corriger les effets de la turbulence atmosphérique est explorée. On présente l'analyse de 79 galaxies observées avec le système d'optique adaptative NaCo du Very Large Telescope (VLT). Les limites sont obtenues grâce à des simulations exhaustives et des comparaisons avec le télescope spatial. Une première estimation de l'évolution morphologique depuis z~1.2 est obtenue à partir de cet échantillon. La comparaison avec les morphologies obtenues avec le télescope spatial laisse entrevoir des différences mais l'échantillon est trop petit pour extraire des conclusions robustes. Un programme d'observations plus large est proposé.
Dans un deuxième temps, des améliorations aux méthodes classiques non-paramétriques d'estimation morphologique sont proposées (nombre illimité de paramètres simultanés, frontières non linéaires) afin de pouvoir analyser des données observées à travers l'atmosphère. On démontre que ces améliorations permettent une estimation morphologique en deux grands types (elliptique, spirale) avec un taux de réussite de ~80% sur des données limitées par le seeing. Le code source a été mis à disposition de la communauté.
La méthode développée est ensuite employée pour analyser un échantillon de ~50000 galaxies dans l'infrarouge proche. L'évolution morphologique depuis z~2 est obtenue et une quantification des effets de k-correction morphologique est présentée par comparaison avec des données spatiales. On observe une augmentation de la fraction de galaxies elliptiques depuis z~2 (~20%) jusqu'à nos jours (~30%). La classification obtenue est globalement en bon accord avec celle obtenue avec des données spatiales dans le visible jusqu'à z~1. Au delà, la classification infrarouge a tendance à trouver ~1.5 fois plus de galaxies précoces.

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17

Laigle, Clotilde. "Observational and theoretical constraints on galaxy evolution at high redshift." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066343.

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Je présente dans cette thèse de nouvelles contraintes sur la formation et l’évolution des galaxies, en étudiant leur croissance en masse et leur évolution au sein de la toile cosmique depuis l’époque de leur formation jusqu’à maintenant. Pour cela, j’ai créé un catalogue photométrique sur le champ COSMOS. Ce catalogue permet de sonder avec précision l’Univers à haut redshift. J’analyse ce relevé observé à l’aide de relevés virtuels, produits à partir de simulations hydrodynamiques. Ces simulations implémentent nos connaissances sur la formation et l’évolution des galaxies.Dans un premier temps, je montre que l’évolution en redshift des propriétés des galaxies est relativement bien comprise en invoquant des processus qui dépendent essentiellement de la masse, tels que le feedback des étoiles et des AGN. Je souligne également comment nos méthodes observationnelles génèrent des biais dans les propriétés physiques des galaxies calculées à partir de la photométrie.Dans un deuxième temps, je montre comment la dynamique des flots de matière à grande échelle gouverne l’acquisition du moment angulaire des galaxies et halos de matière noire, ce qui implique que certaines propriétés des galaxies sont supposées dépendre de leur environnement anisotrope. J’ai extrait la structure filamentaire du catalogue photométrique que j’ai créé sur le champ COSMOS et j’ai mesuré cette dépendance. Je trouve des gradients de masse et de couleurs dans la direction du filament. Il apparaît que la masse et le moment angulaire des galaxies sont deux quantités interdépendantes et tous deux impactés par leur environnement anisotrope
I present in this thesis new constraints on galaxy formation and evolution while studying the galaxy mass growth and the co-evolution of the cosmic web and the embedded galaxies, from the epoch of cosmic dawn to today.To do so, I first created a new photometric catalog on the COSMOS field with precise photometric redshifts allowing to probe accurately the high-redshift Universe. I analyze this survey while relying heavily on comparisons with virtual galaxy surveys produced from state-of-the- art cosmological hydrodynamical simulations, which capture all our current knowledge of galaxy formation and evolution.From this comparative analysis, in the first part of my thesis I show that the redshift evolution of galaxy properties is reasonably well understood when invoking mass-dependent processes (AGN and stellar feed- back). I highlight also the effect of simplifying assumptions inherent to our observational methods, which bias the physical properties computed from galaxy photometry.Galaxies and haloes are embedded in the cosmic web, an intricate large-scale structure of walls, filaments and nodes. In the second part of my thesis, I show how galaxies and dark haloes gain their angular momentum from the large-scale flow, implying that some of their properties depend on their anisotropic filamentary environment. I then extract the filamentary structure from the observed photometric catalog and measure the dependence of galaxy properties to the anisotropic environment. I find mass and colour gradients towards the filaments. In turn it emerges that galaxy masses and angular momenta are two dependent quantities impacted by their anisotropic environment

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18

Lewis, Joseph. "Who reionized the Universe ? : dermining the photon budget of galaxies during reionization with numerical simulations, and studying the impact of dust." Thesis, Strasbourg, 2020. http://www.theses.fr/2020STRAE041.

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La lumière ionisante des premières étoiles a alimenté la Réionisation du milieu intergalactique. Dû au lien entre l’avancée de la Réioinsation et la formation des premières structures, l’étude des galaxies qui réionisent l’Univers a une motivation cosmologique. J’ai cherché à comprendre quelles sont ces galaxies grâce à des simulations numériques. Dans la simulation Cosmic Dawn II, des galaxies de masses intermédiaires de 6x108 à 3x1010 masses solaires propulsent la Réionisation. L’importance de ces galaxies découle de leur nombre, formation stellaire et fractions d’échappement importants. Pour aller plus loin, j’ai implémenté de nouvelles physiques dans le code RAMSESCUDATON, telles que la poussière, et le refroidissement dû aux métaux et à l’Hélium. J’ai aussi modifié la configuration du code pour mieux reproduire les contraintes sur la fraction neutre d’Hydrogène. Il en résulte une Réionisation tardive, qui dépend de galaxies de plus faible masses de 108 à 2x1010 masses solaires. La poussière participe à réduire le rôle des galaxies massives dans la Réionisation, et pourrait affecter les observations des galaxies les plus brillantes pendant la Réionisation. Ces résultats ont des implications importantes pour les observations de galaxies et du gaz réionisant. Les nouvelles physiques et calibration seront utilisées pour Cosmic Dawn III
Ionising light from the first stars drove the Epoch of Reionisation (EoR) of the intergalactic medium. As the progression of the EoR is linked to the formation of the first structures, understanding which galactic sources drive it is cosmologically interesting. I investigated the EoR by studying its galactic sources across time in numerical simulations. I explored which galaxies propel the EoR in Cosmic Dawn II, finding the culprits to be an intermediate mass range of galaxies between 6x108 to 3x1010 solar masses. Their importance is due to its relatively high abundance, high star formation rate, and high escape fractions. To take this answer further, I sought to implement new physics into the code RAMSES-CUDATON (Most importantly, dust, Helium and metal cooling). I also altered the simulation setup to better match constraints on the neutral fraction of Hydrogen. I found that this new configuration supports late Reionisation driven by lower mass galaxies of 108 to 2x1010 solar masses. Dust plays a rôle in reducing the contribution to Reionization of massive galaxies, and could affect observations due to extinction in the brightest galaxies. These results have important implications for observations of reionising galaxies and gas. The new physics and setup with be used in Cosmic Dawn III

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19

Riguccini, Laurie. "Caractériser la formation d'étoiles obscurcie à z ~ 2 dans l'Univers." Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00663803.

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Une fraction non négligeable de l'histoire de la formation stellaire a lieu dans des environnements très affectés par la poussière. Il est donc naturel de se demander si on arrive à bien contraindre cette activité de formation d'étoiles. En effet, une part importante de cette activité pourrait être manquée due à la présence de poussière. C'est dans ce contexte que s'inscrit le travail que je vais présenter.Dans la première partie de ma thèse, j'ai eu pour but de déterminer la fraction de galaxies lumineuses formant des étoiles à haut redshift (i.e. 1.5 1mJy) présentent des couleurs 100/24 et 160/24 plus faibles que les autres sources du champ COSMOS et leur luminosité semble donc provenir majoritairement d'un AGN. Les avancées technologiques et l'exploration des longueurs d'ondes en infra-rouge lointain et en submillimétrique, avec notamment Herschel, SCUBA-2, Alma, JWST, permettront de mieux comprendre la connexion AGN/ flambée de formation stellaire au sein des galaxies jusqu'à des hauts redshifts.

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20

Freundlich, Jonathan. "Star formation across cosmic time and its influence on galactic dynamics." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066459/document.

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Les observations montrent qu'il y a dix milliards d'années, les galaxies formaient bien plus d'étoiles qu'aujourd'hui. Comme les étoiles se forment à partir de gaz moléculaire froid, cela signifie que les galaxies disposaient alors d'importants réservoirs de gaz, et c'est ce qui est observé. Mais les processus de formation d'étoiles pourraient aussi avoir été plus efficaces : qu'en est-il ? Les étoiles se forment dans des nuages moléculaires géants liés par leur propre gravité, mais les toutes premières étapes de leur formation demeurent relativement mal connues. Les nuages moléculaires sont eux-mêmes fragmentés en différentes structures, et certains scénarios suggèrent que les filaments interstellaires qui y sont observés aient pu constituer la première étape de la formation des coeurs denses dans lesquels se forment les étoiles. En quelle mesure leur géométrie filamentaire affecte-t-elle les coeurs pré-stellaires ? Des phenomènes de rétroaction liés à l'évolution des étoiles, comme les vents stellaires et les explosions de supernovae, participent à la régulation de la formation d'étoiles et peuvent aussi perturber la distribution de matière noire supposée entourer les galaxies. Cette thèse aborde l'évolution des galaxies et la formation des étoiles suivant trois perspectives : (i) la caractérisation des processus de formation d'étoiles à des échelles sous-galactiques au moment de leur pic de formation ; (ii) la formation des coeurs pré-stellaires dans les structures filamentaires du milieu interstellaire ; et (iii) les effets rétroactifs de la formation et de l'évolution des étoiles sur la distribution de matière noire des galaxies
Observations show that ten billion years ago, galaxies formed their stars at rates up to twenty times higher than now. As stars are formed from cold molecular gas, a high star formation rate means a significant gas supply, and galaxies near the peak epoch of star formation are indeed much more gas-rich than nearby galaxies. Is the decline of the star formation rate mostly driven by the diminishing cold gas reservoir, or are the star formation processes also qualitatively different earlier in the history of the Universe? Ten billion years ago, young galaxies were clumpy and prone to violent gravitational instabilities, which may have contributed to their high star formation rate. Stars indeed form within giant, gravitationally-bound molecular clouds. But the earliest phases of star formation are still poorly understood. Some scenarii suggest the importance of interstellar filamentary structures as a first step towards core and star formation. How would their filamentary geometry affect pre-stellar cores? Feedback mechanisms related to stellar evolution also play an important role in regulating star formation, for example through powerful stellar winds and supernovae explosions which expel some of the gas and can even disturb the dark matter distribution in which each galaxy is assumed to be embedded. This PhD work focuses on three perspectives: (i) star formation near the peak epoch of star formation as seen from observations at sub-galactic scales; (ii) the formation of pre-stellar cores within the filamentary structures of the interstellar medium; and (iii) the effect of feedback processes resulting from star formation and evolution on the dark matter distribution

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21

Valiante, Elisabetta. "High-redshift infrared galaxies." Diss., lmu, 2008. http://nbn-resolving.de/urn:nbn:de:bvb:19-91747.

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22

Weadock, Julie Louise. "Intermediate redshift radio galaxies." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325935.

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23

Stevens, Robin Edward John. "Searches for high-redshift galaxies." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325616.

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24

Pearce, Henry James. "Massive galaxies at high redshift." Thesis, University of Edinburgh, 2012. http://hdl.handle.net/1842/6228.

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A unique K-band selected high-redshift spectroscopic dataset (UDSz) is exploited to gain further understanding of galaxy evolution at z > 1. Acquired as part of an ESO Large Programme, this thesis presents the reduction and analysis of a sample of ∼ 450 deep optical spectra of a random 1 in 6 sample of the KAB < 23, z > 1 galaxy population. Based on the final reduced dataset, spectrophotometric modelling of the optical spectra and multi-wavelength photometry available for each galaxy is performed using a combination of single and dual component stellar population models. The stellarmass and age estimates provided by the spectrophotometric modelling are exploited throughout the rest of the thesis to investigate the evolution of massive galaxies at z > 1. Focusing on a K-band bright (K < 21.5) sub-sample in the redshift range 1.3 < z < 1.5 the galaxy size-mass relation has been studied in detailed. In agreement with some previous studies it is found that massive, old, early-type galaxies (ETGs) have characteristic radii a factor ~- 1.5 − 3.0 smaller than their local counterparts at a given stellar-mass. Due to the potential errors in spectrophotometric estimates of the stellarmasses at high redshift velocity dispersion measurements are derived for a sub-sample of massive ETGs at z > 1.3 in order to calculate dynamical mass estimates. To date, only a handful of objects at z > 1.3 have individual velocity dispersion estimates in the literature. Here the largest single sample (13 objects) of velocity dispersion measurements at high redshift is presented. The results for the sub-sample of objects with dynamical mass estimates confirm the results based on stellar mass estimates that high redshift massive systems are more compact than their local counterparts. The fraction of K-band bright objects at high redshift that are passively evolving is calculated with specific star-formation rates from the UV rest-frame continuum, [OII] emission and 24μm data. It is concluded that ∼ 58 ± 10% of the K < 21.5, 1.3 < z < 1.5 galaxy population is passively evolving. Various photometric techniques for separating star-forming and passively evolving galaxies are assessed by exploiting the accurate spectral types derived for the UDSz spectroscopic sample. Popular highredshift selection techniques are shown to fail to effectively select complete samples of passive objects with low levels of contamination. Using detailed information available for the UDSz dataset, various techniques are optimised and then used to estimate the passive fraction from the full UDS photometric catalog. The passive fraction results from the full photometric catalog are found to agree well with the results derived from the UDSz sample. With the Visible and Infrared Survey Telescope for Astronomy (VISTA) now starting to produce data, the opportunity has been taken to develop high-redshift galaxy population dividers based on the VISTA filters. Using the first data release from the VISTA Deep Extragalactic Observations (VIDEO) survey (VVDS D1 field), the passive fractions of K-band limited samples have been estimated to compare with results derived in the UDS. Within the errors the passive fraction estimates in the UDS and VISTA VVDS D1 field are found to agree reasonably well. Finally, composite spectra are used to study the evolution of various different galaxy sub-samples as a function of redshift, age, stellar-mass and specific star-formation rate. This work produces an remarkably clean result, showing that the massive, absolute Kband bright, passively evolving ETGs are always the oldest population, with ages close to the age of the Universe at z ∼ 1.4. In contrast, the late-type, low-mass, star-forming galaxies are always found to be much younger systems. This result strongly supports the downsizing scenario, in which more massive systems complete their stellar-mass assembly before lower-mass counterparts.

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25

Maier, Christian. "Emission line galaxies from CADIS high redshift Lyman-[alpha] [Lyman-alpha] galaxies and metal poor galaxies at medium redshift /." [S.l. : s.n.], 2002. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB10358880.

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26

Weatherley, Stephen John. "Selected observations of high-redshift galaxies." Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414480.

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27

McLeod, Brian Andrew. "Infrared imaging of high-redshift galaxies." Diss., The University of Arizona, 1994. http://hdl.handle.net/10150/186985.

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First we present new infrared counts of field galaxies from more than 20 square arcminutes to a limiting magnitude of K = 20 and from 2 square arcminutes to K = 21.5. At the faintest magnitudes the counts are slightly higher than those reported previously, though still consistent given the small numbers of galaxies in the two samples. Next we present models predicting the magnitude, redshift and color distributions of field galaxies. We explore whether a fading starburst scenario can account for the observations of faint blue galaxies. We marginally rule out a starburst scenario with a local IMF because the models predict too many nearby faint galaxies that are not observed. A burst model with a truncated IMF reproduces the counts and redshift distributions well but produces too blue a population. We show that surface brightness selection has a significant effect on the distributions. In particular, adding a population of low-surface brightness galaxies, known to exist locally, can explain the counts for B(J) < 23. Finally we show that the colors of galaxies in a K-band selected sample are not consistent with a passive evolution model. In the final section we consider the effects of radio power on a sample of galaxies around z = 1. We have obtained BRJHK images of 25 galaxies from the MIT-Green Bank (MG) radio survey. Compared with a sample of more powerful 3CR radio galaxies, these galaxies are 0.5 mag fainter when measured in 8" apertures but not noticeably fainter in 4" apertures. This implies that the near environments of galaxies are correlated with radio power. The MG sample contains galaxies that are just as blue as the bluest 3CR galaxies, but the median MG galaxy is slightly redder than the median 3CR galaxy at the same redshift.

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28

Hayward, Christopher. "Physically Modeling High-Redshift Ultraluminous Infrared Galaxies." Thesis, Harvard University, 2011. http://dissertations.umi.com/gsas.harvard:10008.

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We have used a combination of hydrodynamical simulations, dust radiative transfer, and an empirically based analytical model for galaxy number densities and merger rates in order to physically model the bright high-redshift submillimeter-selected galaxy (SMG) population. We report the results of three projects: In the first we study the dependence of a galaxy’s observed-frame submillimeter (submm) flux on its physical properties. One of our principal conclusions is that the submm flux scales significantly more weakly with star formation rate for starbursts than for quiescently star-forming galaxies. Consequently, we argue that the SMG population is not exclusively merger-induced starbursts but rather a mix of merger-induced starbursts, early-stage mergers where two quiescently star-forming disk galaxies are blended into one submm source ("galaxy-pair SMGs"), and isolated disk galaxies. In the second work we present testable predictions of this model by demonstrating how quiescently star-forming and starburst SMGs can be distinguished from integrated data alone. Starbursts tend to have higher luminosity, effective dust temperature, global star formation efficiency $(L_{IR}/M_{gas})$, and infrared excess $(L_{IR}/L_{FUV})$ and tend to lie significantly above the star formation rate-stellar mass relation deﬁned by quiescently star-forming galaxies. These diagnostics can be used to observationally determine the relative contribution of quiescently star-forming and starburst galaxies to the SMG population. In the final work we present the SMG number density, cumulative number counts, and redshift distribution predicted by our model. We show that, contrary to previous claims, the observed SMG number counts do not provide evidence for a top-heavy initial mass function. We also show that starbursts and galaxy-pair SMGs both contribute significantly to the bright SMG counts, whereas isolated disks contribute significantly only at the faint end.
Astronomy

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29

Crawford, Miller. "Modelling galaxies in the high redshift universe." Thesis, University of Edinburgh, 2006. http://hdl.handle.net/1842/27834.

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I present predictions for the high redshift universe, where dust is known to play an important role in influencing the observed magnitudes, colours and properties of galaxies. I demand that an acceptable model must first yield reasonably accurate predictions for the local universe before being tested at high redshift. Not only will this ground the models in reality, it will then help assess whether a ‘standard’ semi-analytic model can reproduce facets of the high redshift universe without recourse to new physics. I construct mock surveys in an attempt to account for three distinct classes of object: Lyman Break Galaxies (LBGs), a population of dusty star forming galaxies at redshift 3, Extremely Red Objects (EROs), galaxies with (R-K) > 5 uncovered in deep K-band surveys, and Submillimetre Galaxies (SMGs) detected in blank field SCUBA surveys. Global trends and individual galaxy properties are explored and compared with reality. Overlaps between distinct populations are investigated, and the fate of extreme high redshift objects is followed through time, shedding light on relationships between evolutionary phases of galaxies. It has been suggested that SMGs and EROs are the progenitors of local giant ellipticals, and I can assess the validity of this theory within the framework of the simulated survey volumes. SMGs are among the most massive objects present at that particular point in cosmic history. Such extreme objects will be highly biased towards over densities in the dark matter field, and thus should exhibit strong clustering. The SCUBA Half-Degree Extragalactic Survey (SHADES) aims to detect a statistically significant number of SMGs with an unambiguous measure of their clustering properties in mind. I present equivalent predictions for the model SMGs, a technique that has great potential in assisting the planning and interpretation of future deep surveys aimed at probing the earliest stages of galaxy formation and the origins of the most massive galaxies we see today.

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30

Simard, Luc. "The internal kinematics of intermediate redshift galaxies." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1996. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq21948.pdf.

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31

Cruz, Maria JoseÌ. "Steep-spectrum radio galaxies at high redshift." Thesis, University of Oxford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.427877.

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32

Inskip, Katherine Jane. "The evolution of high redshift radio galaxies." Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.619533.

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33

Lowenthal, James Daniel. "Line emission from galaxies at high redshift." Diss., The University of Arizona, 1991. http://hdl.handle.net/10150/185621.

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The results of a multi-faceted search for spectral line emission from galaxies at high redshift are presented. Deep two-dimensional spectra of four blank sky fields were taken at the Multiple Mirror Telescope (MMT) at wavelengths corresponding to redshifted Lyα emission in the range 2.7 < z < 4.7, and the resulting non-detections are used to place upper limits on the space density of randomly distributed Lyα emitters. Although the predictions of a conservative model of galaxy formation incorporating cold dark matter are not excluded in a statistical sense, the search would have detected star-forming dwarf galaxies comparable to the Magellanic Clouds at z = 3, given minimal extinction by dust. The Goddard Fabry-Perot Imager, a piezo-electrically controlled tunable narrow-band filter system with a stand-alone CCD system, was developed and tested, and used at the Kitt Peak National Observatory (KPNO) 4 m telescope to image the damped Lyα absorbing clouds towards three high-redshift QSOs in the light of redshifted Lyα. A companion galaxy to one of the damped systems was discovered and confirmed with followup spectroscopy, and its properties are presented and discussed; the companion exhibits strong Lyα and weak C IV λ1549 and He II λ1640 emission lines, and is apparently producing stars at a rate SFR ∼ 5 - 10M(⊙) yr⁻¹. The implications of the companion's proximity to the damped cloud are analyzed in view of the previous non-detections, and a lower limit to the spatial correlation function of the damped Lyα systems with galaxies is given. Spectroscopic limits on Lyα emission from seven damped systems, including some known to have low chemical and dust abundances, imply low levels of star formation, SFR ≲ 1 M(⊙) yr⁻¹, but extinction by dust in some cases may cause an underestimation of these rates. With near-infrared spectrographs at the MMT and the KPNO 4 m, eight damped Lyα systems were searched for spectral lines characteristic of star formation regions but redshifted from the optical into the near-infrared. A possible detection of (O II) λ3727 and Hβ from one system implies a star formation rate on the order of 100 M(⊙) yr⁻¹, though the remainder of the observations produced non-detections compatible with the Lyα emission limits. The implications for galaxy formation and evolution at high redshift are discussed.

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34

Sarajedini, Vicki Lynn 1968. "Compact nuclei in galaxies at moderate redshift." Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/288717.

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The purpose of this study is to understand the space density and properties of active galaxies to z ∼eq 0.8. We have investigated the frequency and nature of unresolved nuclei in galaxies at moderate redshift as indicators of nuclear activity such as Active Galactic Nuclei (AGN) or starbursts. Candidates are selected by fitting imaged galaxies with multi-component models using maximum likelihood estimate techniques to determine the best model fit. We select those galaxies requiring an unresolved, point source component in the galaxy nucleus, in addition to a disk and/or bulge component, to adequately model the galaxy light.

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35

Sjöbom, Ludvig. "The ultraviolet spectral slope of high-redshift galaxies." Thesis, Uppsala universitet, Observationell astrofysik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-310603.

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The slope of the ultraviolet continuum emissions from a galaxy between 1250 and 2600 Å provides insights about several facets of the galaxy. Mainly, it is well-correlated with the amount of dust. This work presents a search for objects whose UV-continuum slopes are excessively steep, as well as suggestions for follow-up. The method used is looking through existing data sets, and proposing follow-up of the outliers in the distribution of slopes. Close to fifteen objects with slopes beyond what is easily explained by theory are presented. Since these lie beyond the realm of current theories, confirmations of these may hint at more extreme stellar populations than those currently known. This may include excessively metal-poor stars such as population III stars, or stellar populations where the initial mass function (IMF) for some reason may be biased towards massive stars. Steeper slopes are in general indicative of a lack of dust and an abundance of hot, blue stars; this is due to the reddening caused by dust, and emissions from cooler stars being peaked at longer wavelengths.

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36

Su, T., T. A. Marriage, V. Asboth, A. J. Baker, J. R. Bond, D. Crichton, M. J. Devlin, et al. "On the redshift distribution and physical properties of ACT-selected DSFGs." OXFORD UNIV PRESS, 2017. http://hdl.handle.net/10150/623115.

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We present multi-wavelength detections of nine candidate gravitationally lensed dusty starforming galaxies (DSFGs) selected at 218 GHz (1.4 mm) from the Atacama Cosmology Telescope (ACT) equatorial survey. Among the brightest ACT sources, these represent the subset of the total ACT sample lying in Herschel SPIRE fields, and all nine of the 218 GHz detections were found to have bright Herschel counterparts. By fitting their spectral energy distributions (SEDs) with a modified blackbody model with power-law temperature distribution, we find the sample has a median redshift of z = 4.1(-1.0)(+1.1) (68 per cent confidence interval), as expected for 218 GHz selection, and an apparent total infrared luminosity of log10(mu LIR/L-circle dot) = 13.86(-0.30)(+0.33), which suggests that they are either strongly lensed sources or unresolved collections of unlensed DSFGs. The effective apparent diameter of the sample is root mu d = 4.2(-1.0)(+1.7) kpc, further evidence of strong lensing or multiplicity, since the typical diameter of DSFGs is 1.0-2.5 kpc. We emphasize that the effective apparent diameter derives from SED modelling without the assumption of optically thin dust (as opposed to image morphology). We find that the sources have substantial optical depth (tau = 4.2(-1.9)(+3.7)) to dust around the peak in the modified blackbody spectrum (lambda(obs) <= 500 mu m), a result that is robust to model choice.

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37

Best, P. N. "The 3CR radio galaxies at redshift z ˜ 1." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596601.

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Hubble Space Telescope (HST) observations are presented for a sample of 28 3CR radio galaxies in the redshift range 0.6 < z < 1.8, together with maps of their radio structure at comparable angular resolution obtained using the VLA interferometer, and infrared images of the field taken with UKIRT. The HST images display a wide range of bizarre structures which tend to be aligned along the radio axis. The morphology of the optical emission evolves strongly with the physical size of the radio source, suggesting that the predominant cause of the optical alignment is a massive burst of star formation induced by shocks associated with the passage of the radio hotspots through the host galaxy. Such a starburst would evolve and fade throughout the lifetime of the radio source. This model is supported by the HST observations of 3C34, which provide evidence for such a burst of star formation having been induced in a companion galaxy by the impact of the radio jet. In contrast, the infrared images show giant elliptical galaxies. The radial intensity profiles of the galaxies are well-matched at radii ≤ 30 kpc by a de Vaucouleur's law, whilst at greater radii they show an excess of emission similar to that of cD galaxy halos. Their infrared K-magnitudes are tightly correlated with redshift, consistent with them being a passively evolving population of galaxies which formed at high redshift. Passive evolution of their stellar populations is also required if their surface brightness vs characteristic size relation is to match the fundamental plane defined by low redshift giant elliptical galaxies. The implications of these results for the formation and evolution of massive galaxies and for the cosmic evolution of the radio source population are discussed.

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38

Wei, Jun-Jie, Xue-Feng Wu, Fulvio Melia, Fa-Yin Wang, and Hai Yu. "THE AGE–REDSHIFT RELATIONSHIP OF OLD PASSIVE GALAXIES." IOP PUBLISHING LTD, 2015. http://hdl.handle.net/10150/615092.

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We use 32 age measurements of passively evolving galaxies as a function of redshift to test and compare the standard model ($\Lambda$CDM) with the $R_{\rm h}=ct$ Universe. We show that the latter fits the data with a reduced $\chi^2_{\rm dof}=0.435$ for a Hubble constant $H_{0}= 67.2_{-4.0}^{+4.5}$ km $\rm s^{-1}$ $\rm Mpc^{-1}$. By comparison, the optimal flat $\Lambda$CDM model, with two free parameters (including $\Omega_{\rm m}=0.12_{-0.11}^{+0.54}$ and $H_{0}=94.3_{-35.8}^{+32.7}$ km $\rm s^{-1}$ $\rm Mpc^{-1}$), fits the age-\emph{z} data with a reduced $\chi^2_{\rm dof}=0.428$. Based solely on their $\chi^2_{\rm dof}$ values, both models appear to account for the data very well, though the optimized $\Lambda$CDM parameters are only marginally consistent with those of the concordance model ($\Omega_{\rm m}=0.27$ and $H_{0}= 70$ km $\rm s^{-1}$ $\rm Mpc^{-1}$). Fitting the age-$z$ data with the latter results in a reduced $\chi^2_{\rm dof}=0.523$. However, because of the different number of free parameters in these models, selection tools, such as the Akaike, Kullback and Bayes Information Criteria, favour $R_{\rm h}=ct$ over $\Lambda$CDM with a likelihood of $\sim 66.5\%-80.5\%$ versus $\sim 19.5\%-33.5\%$. These results are suggestive, though not yet compelling, given the current limited galaxy age-$z$ sample. We carry out Monte Carlo simulations based on these current age measurements to estimate how large the sample would have to be in order to rule out either model at a $\sim 99.7\%$ confidence level. We find that if the real cosmology is $\Lambda$CDM, a sample of $\sim 45$ galaxy ages would be sufficient to rule out $R_{\rm h}=ct$ at this level of accuracy, while $\sim 350$ galaxy ages would be required to rule out $\Lambda$CDM if the real Universe were instead $R_{\rm h}=ct$. This difference in required sample size reflects the greater number of free parameters available to fit the data with $\Lambda$CDM.

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39

Jones, Suzy Frederica. "Submillimetre observations of dusty, luminous, high-redshift galaxies." Thesis, University of Leicester, 2015. http://hdl.handle.net/2381/32899.

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This thesis presents submillimetre (submm) observations using the James Clerk Maxwell Telescope (JCMT) Submillimetre Common-User Bolometer Array 2 (SCUBA-2) of dusty, luminous, high-redshift galaxies. Submm wavelengths are important because the coldest dust properties can be observed, which can help with the calculation of total infrared (IR) luminosities. Three samples of galaxies are investigated in Chapters 3, 4 and 6. The galaxies in Chapter 3 are selected using the Wide-Field Infrared Survey Explorer (WISE) with extremely red mid-IR colours. From previous studies these galaxies are a rare population of dusty, hot (60 - 120K), high-redshift 1 < z < 3, hyper-luminous galaxies and are known as hot dust-obscured galaxies (WISE-selected Hot DOGs). The galaxies in Chapter 4 are selected in a comparable method but are also radio-selected. These galaxies with radio emission are thought to have radio-jet dominated feedback. The galaxies from Chapter 3 and 4 are amongst the most luminous galaxies in the Universe and could be undergoing intense AGN-driven feedback. This feedback could be the result of major mergers between two gas-rich galaxies and are thought to be an important mechanism in galaxy evolution. Chapter 5 compares the two samples of galaxies in Chapters 3 and 4 and also their environments. The environments around high-redshift far-IR and mid-IR luminous galaxies appears to be above average. The overdense environments could yield evidence for the nature of their massive dark matter halos and highlight their bias as compared with the underlying dark matter distribution. The galaxies in Chapter 6 were selected in the millimetre (mm) wavelengths using Planck to have dusty spectral energy distributions (SEDs). Submm observations are used to determine if they are candidates for dusty, luminous, high-redshift galaxies and to obtain more accurate positions. Consequently this will help future searches of dusty, luminous, high-redshift galaxies using successive all-sky Planck data releases.

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40

Trebitsch, Maxime. "Transfert radiatif dans les galaxies à Grand Redshift." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1119/document.

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L'époque de la réionisation, qui s'étend pendant le premier milliard d'années de l'Univers, correspond à la période où les premières étoiles et galaxies apparaissent. Dans ce contexte, l'enjeu majeur de cette thèse est d'étudier la formation de ces premières structures et leur rétroaction radiative sur leur environnement. Pour cela, j'utilise différentes méthodes de simulations numériques permettant de modéliser le transfert radiatif dans les galaxies, dans un cadre cosmologique.En particulier, les plus petites galaxies seraient celles qui apportent la majorité des photons nécessaires à ioniser l'Univers. J'explore cette hypothèse dans une première partie à l'aide de simulations radio-hydrodynamiques avec le code RAMSES-RT, ciblant trois petites galaxies avec une très haute résolution spatiale et temporelle. Je me suis d'abord intéressé aux mécanismes régulant la production et le transfert de photons ionisants dans les galaxies, et j'ai montré que les explosions de supernovae en sont un facteur essentiel. Ensuite, j'ai exploré les propriétés observables dérivées à partir de ces simulations.Dans un second temps, j'ai développé une extension au code Monte Carlo de transfert radiatif MCLya prenant en compte la polarisation du rayonnement et l'émission diffuse dans une simulation. J'ai utilisé ce code pour post-traiter une simulation d'un blob Lyman-alpha, une source étendue d'émission Lyman-alpha, et étudier ses propriétés de polarisation à l'aide de pseudo-observations. Contrairement à ce qui était proposé précédemment, j'ai pu montrer que la polarisation n'était pas un indicateur aussi utile qu'espéré pour tracer l'origine des photons Lyman-alpha
The Epoch of Reionisation, which spans during the first billion year of te Universe, corresponds to the period during which the first stars and galaxy form. In this context, the main topic of this thesis is to study the formation of those early structures and their radiative feedback to their environment. For this purpose, I use various numerical simulations tools designed to model the radiative transfer in galaxies in a cosmological framework.More specifically, I look at very small galaxies, which are believed to contribute the bulk of the photons required to reionise the Universe. I explore this idea using radiative hydrodynamics simulations performed with RAMSES-RT, focusing on three small galaxies with a very high spatial and temporal resolution. I first detail the mechanism that regulate te production and escape of ionising photons in galaxies, and I show that supernovae explosions are a crucial element for this regulation. I then started to investigate the observable properties of those galaxies.In a second part of my thesis, I developped an extension to the Monte Carlo radiative transfer code MCLya to take light polarisation into account and to model the diffuse emission. I applied this code to post-process the simulation of a Lyman-alpha blob (an extended Lyman-alpha source), and to study its polarisation properties with mock observations. Contrary to what was suggested before, I showed that polarisation is not a strong tracer of the origin of Lyman-alpha photons

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Tadros-Attalla, Helen. "Power spectrum analysis of redshift surveys." Thesis, University of Oxford, 1996. https://ora.ox.ac.uk/objects/uuid:5a5786db-748e-4c78-bab8-c89a4eda2f07.

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This thesis describes a study of the clustering properties of galaxies and clusters of galaxies as measured by the power spectrum (P(k)) and the counts in cells statistic. The samples used are the optical Stromlo-APM galaxy survey, the APM cluster survey and the IRAS 1.2Jy, QDOT and PSCz surveys. Throughout, N-body simulations, for a variety of cosmological models, are used to test methods and to supplement analytic error estimates. For the Stromlo-APM sample the amplitude of the power spectrum is dependent on galaxy morphology. Early-type galaxies show a higher clustering amplitude than late-type galaxies by a factor of ~ 1.8. There is also tentative evidence for some dependence of the clustering amplitude on galaxy luminosity. The parameter Ω0.6/b is estimated via a comparison with the real-space power spectrum of the two-dimensional APM galaxy survey. For APM clusters the power spectrum is measured to very small wave numbers, with a possible detection of the expected turn-over. The results are inconsistent with the standard cold dark matter model. The shape of P( k) for clusters is approximately the same as that for Stromlo-APM galaxies but amplified by a factor of ~ 3.5. The power spectrum of the QDOT sample depends sensitively on the galaxy weighting scheme, probably due the manner in which the region of the Hercules supercluster is sampled. A best estimate of the power spectrum of IRAS galaxies is computed by combining the IRAS l.2Jy and QDOT samples. The PSCz galaxy power spectrum is also computed. The PSCz galaxies have a clustering amplitude twice that of optical galaxies. A similar result is found from a joint counts in cells analysis. Redshift-space distortions in the PSCz sample are analysed using a spherical harmonic decomposition of the density field. The value of Ω0.6/b = 1 is ruled out by this analysis at the 2σ significance level.

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Bezanson, Rachel, David A. Wake, Gabriel B. Brammer, Pieter G. van Dokkum, Marijn Franx, Ivo Labbé, Joel Leja, et al. "LEVERAGING 3D-HST GRISM REDSHIFTS TO QUANTIFY PHOTOMETRIC REDSHIFT PERFORMANCE." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/621218.

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We present a study of photometric redshift accuracy in the 3D-HST photometric catalogs, using 3D-HST grism redshifts to quantify and dissect trends in redshift accuracy for galaxies brighter than JH(IR) > 24 with an unprecedented and representative high-redshift galaxy sample. We find an average scatter of 0.0197 +/- 0.0003(1 + z) in the Skelton et al. photometric redshifts. Photometric redshift accuracy decreases with magnitude and redshift, but does not vary monotonically with color or stellar mass. The 1 sigma scatter lies between 0.01 and 0.03 (1 + z) for galaxies of all masses and colors below z. <. 2.5 (for JH(IR) < 24), with the exception of a population of very red (U - V > 2), dusty star-forming galaxies for which the scatter increases to similar to 0.1 (1+ z). We find that photometric redshifts depend significantly on galaxy size; the largest galaxies at fixed magnitude have photo-zs with up to similar to 30% more scatter and similar to 5 times the outlier rate. Although the overall photometric redshift accuracy for quiescent galaxies is better than that for star-forming galaxies, scatter depends more strongly on magnitude and redshift than on galaxy type. We verify these trends using the redshift distributions of close pairs and extend the analysis to fainter objects, where photometric redshift errors further increase to similar to 0.046 (1 + z) at H-F160W = 26. We demonstrate that photometric redshift accuracy is strongly filter dependent and quantify the contribution of multiple filter combinations. We evaluate the widths of redshift probability distribution functions and find that error estimates are underestimated by a factor of similar to 1.1 - 1.6, but that uniformly broadening the distribution does not adequately account for fitting outliers. Finally, we suggest possible applications of these data in planning for current and future surveys and simulate photometric redshift performance in the Large Synoptic Survey Telescope, Dark Energy Survey (DES), and combined DES and Vista Hemisphere surveys.

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43

Zhang, Huanian, Dennis Zaritsky, Guangtun Zhu, Brice Ménard, and David W. Hogg. "HYDROGEN EMISSION FROM THE IONIZED GASEOUS HALOS OF LOW-REDSHIFT GALAXIES." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/622684.

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Using a sample of nearly half a million galaxies, intersected by over 7 million lines of sight from the Sloan Digital Sky Survey Data Release 12, we trace H alpha + [N II] emission from a galactocentric projected radius, r(p), of 5 kpc to more than 100 kpc. The emission flux surface brightness is alpha r(p) 1.9 +/- 0.4. We obtain consistent results using only the Ha or [N II] flux. We measure a stronger signal for the bluer half of the target sample than for the redder half on small scales, r(p) < 20 kpc. We obtain a 3 sigma detection of H alpha + [N II] emission in the 50-100 kpc r(p) bin. The mean emission flux within this bin is (1.10 +/- 0.35) x 10(-20) erg cm(-2) s(-1) angstrom(-1), which corresponds to 1.87 x 10(-20) erg cm(-2) s(-1) arcsec(-2) or 0.0033 Rayleigh. This detection is 34 times fainter than a previous strict limit obtained using deep narrow-band imaging. The faintness of the signal demonstrates why it has been so difficult to trace recombination radiation out to large radii around galaxies. This signal, combined with published estimates of n(H), leads us to estimate the temperature of the gas to be 12,000 K, consistent with independent empirical estimates based on metal ion absorption lines and expectations from numerical simulations.

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44

Quider, Anna Marie. "High redshift star-forming galaxies in absorption and emission." Thesis, University of Cambridge, 2011. https://www.repository.cam.ac.uk/handle/1810/239408.

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Galaxies in the redshift range 1 < z < 3 existed during the most vigorous period of star formation in the history of the Universe. In the past 15 years, large rest-frame UV spectroscopic samples of z ~ 3 star-forming galaxies have been assembled. However, this particular redshift range, the so-called Redshift Desert, has only begun to be characterized. Most studies involve low resolution, low signal-to-noise spectra because the small angular size (δ ≤ 1") and faintness (RAB = 24 - 25.5) of high redshift galaxies limit what can be accomplished with a reasonable investment of observing time, even using the world's largest optical telescopes. One way to circumvent these two issues is to study gravitationally lensed galaxies. The magnification boost (up to a factor of 30x) and morphological distortion of a high redshift galaxy by an intervening mass concentration allow for the study of the high redshift Universe in unprecedented detail. I present a detailed analysis of the rest-UV spectrum of two gravitationally lensed galaxies: the 'Cosmic Horseshoe' (zsys = 2.38115) and the 'Cosmic Eye' (zsys = 3.07331). The characterization of the stellar populations and the interstellar gas geometry, kinematics, and composition which I achieve is a preview of the type of information that will be available for unlensed high redshift galaxies with the next generation of optical telescopes. I probe the lower redshift end of the Redshift Desert with a study of Fe ii and Mg ii features in the rest-frame near-UV spectrum of 96 star-forming galaxies in the redshift range 1 < z < 2. Stacked spectra are used to explore average outflow and line profile trends with stellar mass and reddening. I also investigate the phenomenon of emission filling of absorption lines which has implications for the line strength and velocity offset of interstellar absorption lines. Individual galaxies are used to assess the range of outflow velocities as well as the prevalence of emission filling in galaxies from this epoch. This is the first large scale study of fine-structure emission from Feii in high redshift galaxies, both in stacked and individual galaxy spectra. An alternative to investigating galaxies by collecting their light is to study them as seen in absorption against a cosmic backlight, such as a quasar. The Sloan Digital Sky Survey, an imaging and spectroscopic survey which covers about one-quarter of the night sky, has collected many thousands of quasar spectra. I search ~ 44,600 of these spectra, up through Data Release 4, for Mg ii λλ2796,2803 absorption doublets. The final catalog includes ~ 16700 Mgii absorption line systems in the redshift range 0.36 ≤ z ≤ 2.28. Measurements of the absorption redshift and rest equivalent widths of the Mg ii doublet as well as select metal lines are available in the catalog. This is the largest publicly available catalog of its kind and its combination of large size and well understood statistics make it ideal for precision studies of the low-ionization and neutral gas regions of galaxies. I conclude this thesis by suggesting several avenues for extending the studies of high redshift star-forming galaxies presented herein.

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45

Bisigello, L., K. I. Caputi, L. Colina, O. Le Fèvre, H. U. Nørgaard-Nielsen, P. G. Pérez-González, J. Pye, et al. "THE IMPACT OF JWST BROADBAND FILTER CHOICE ON PHOTOMETRIC REDSHIFT ESTIMATION." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/622361.

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The determination of galaxy redshifts in the James Webb Space Telescope's (JWST) blank-field surveys will mostly rely on photometric estimates, based on the data provided by JWST's Near-Infrared Camera (NIRCam) at 0.6-5.0 mu m and Mid Infrared Instrument (MIRI) at lambda > 5.0 mm. In this work we analyze the impact of choosing different combinations of NIRCam and MIRI broadband filters (F070W to F770W), as well as having ancillary data at lambda < 0.6 mu m, on the derived photometric redshifts (z(phot)) of a total of 5921 real and simulated galaxies, with known input redshifts z = 0-10. We found that observations at lambda < 0.6 mm are necessary to control the contamination of high-z samples by low-z interlopers. Adding MIRI (F560W and F770W) photometry to the NIRCam data mitigates the absence of ancillary observations at l < 0.6 mm and improves the redshift estimation. At z = 7-10, accurate zphot can be obtained with the NIRCam broadbands alone when S/N >= 10, but the z(phot) quality significantly degrades atb S/N <= 5. Adding MIRI photometry with 1 mag brighter depth than the NIRCam depth allows for a redshift recovery of 83%-99%, depending on spectral energy distribution type, and its effect is particularly noteworthy for galaxies with nebular emission. The vast majority of NIRCam galaxies with [F150W] = 29. AB mag at z =7-10 will be detected with MIRI at [F560W, F770W] < 28 mag if these sources are at least mildly evolved or have spectra with emission lines boosting the mid-infrared fluxes.

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46

Bisigello, L., K. I. Caputi, L. Colina, Fèvre O. Le, H. U. Nørgaard-Nielsen, P. G. Pérez-González, der Werf P. van, O. Ilbert, N. Grogin, and A. Koekemoer. "Recovering the Properties of High-redshift Galaxies with Different JWST Broadband Filters." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/624902.

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Imaging with the James Webb Space Telescope (JWST) will allow observations of the bulk of distant galaxies at the epoch of reionization. The recovery of their properties, such as age, color excess E(B-V), specific star formation rate (sSFR), and stellar mass, will mostly rely on spectral energy distribution fitting, based on the data provided by JWST's two imager cameras, namely the Near Infrared Camera (NIRCam) and the Mid Infrared Imager (MIRI). In this work we analyze the effect of choosing different combinations of NIRCam and MIRI broadband filters, from 0.6 to 7.7 mu m, on the recovery of these galaxy properties. We performed our tests on a sample of 1542 simulated galaxies, with known input properties, at z = 7-10. We found that, with only eight NIRCam broadbands, we can recover the galaxy age within 0.1 Gyr and the color excess within 0.06 mag for 70% of the galaxies. Additionally, the stellar masses and sSFR are recovered within 0.2 and 0.3 dex, respectively, at z = 7-9. Instead, at z = 10, no NIRCam band traces purely the lambda > 4000 angstrom regime and the percentage of outliers in stellar mass (sSFR) increases by > 20% (> 90%), in comparison to z = 9. The MIRI F560W and F770W bands are crucial to improve the stellar mass and the sSFR estimation at z = 10. When nebular emission lines are present, deriving correct galaxy properties is challenging at any redshift and with any band combination. In particular, the stellar mass is systematically overestimated in up to 0.3 dex on average with NIRCam data alone and including MIRI observations only marginally improves the estimation.

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47

Mitchell, Ewan Keith. "A sample of radio galaxies at redshift z~0.5." Thesis, University of Oxford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.442823.

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48

Flynn, Stephen. "AzTEC and Spitzer investigations of high redshift submillimetre galaxies." Thesis, Cardiff University, 2011. http://orca.cf.ac.uk/12383/.

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Submillimetre galaxies are an important element in the history of the universe. There have been great advances in technology in the last ten years that have enabled deeper and more detailed investigations of these distant objects. In thisthesis I describe investigations of the properties of high redshift submillimetre galaxies made using data from multiple surveys and multiple instruments. Firstly I describe the process involved in reducing AzTEC data to produce images. I then present the reduced maps and compare them, along with a source catalogue, to those produced by the AzTEC instrument team. I found both reductions produce broadly similar results with some differences that can be explained by slightly different sets of input maps. I then present an analysis of the fainter objects in one of the AzTEC fields using a stacking technique. This analysis determines the contribution Spitzer detected galaxies make to the background at 1.1mm, the redshift dependence of this contribution and the average dust mass that can be associated with it. I also describe an analysis of the ux ratios Eales et al. (2003)found using the available AzTEC data and Spitzer IRAC imaging. In the the penultimate chapter I describe the frequentist identification technique I used to determine counterparts to SCUBA submillimetre sources in the CUDSS three hour field using Spitzer infrared data.

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49

Mountrichas, Georgios. "QSOs and galaxies : lensing, clustering and redshift-space distortions." Thesis, Durham University, 2008. http://etheses.dur.ac.uk/2246/.

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The aim of this thesis is to analyze statistically the available QSO, LRG, galaxy and cluster samples in order to estimate the QSO-galaxy lensing anti-correlation signal and measure the mass of foreground galaxies and clusters and to estimate the QSO-LRG clustering amplitude, the QSO bias and their dependence on QSO luminosity. We also investigate the behaviour of the group-galaxy infall parameter and their rms velocity dispersions for different group memberships. The aim here is to make dynamical estimates of the group masses to check the QSO lensing results. We first cross-correlate the SDSS photo-z, g < 21, 1.0 < Z(_p) < 2.2 QSOs with g < 21 galaxies and clusters in the same areas. The anti-correlation found is somewhat less than the results of Myers et al. based on 2QZ QSOs. But contamination of the QSOs by low redshift NELGs and QSOs can cause underestimation of the anticorrelation lensing signal. Correcting for such low redshift contamination at the levels indicated by our spectroscopic checks suggests that the effect is generally small for QSO cross-correlations with g < 21 galaxies but may be an issue for fainter galaxy samples. Thus when this correction is applied to the photo-z QSO sample of Scranton et al. the anti-correlation increases and the agreement with the 2QZ results of Myers et al. is improved. When we also take into account the fainter r < 21 galaxy limit of Scranton et al. as opposed to g < 21 for Myers et al., the two observational results appear to be in very good agreement. We then measure the bias of QSOs as a function of QSO luminosity at fixed redshift (z < 1) by cross-correlating them with Luminous Red Galaxies (LRGs) in the same spatial volume, hence breaking the degeneracy between QSO luminosity and redshift. We use three QSO samples from 2SLAQ, 2QZ and SDSS covering a QSO absolute magnitude range -24.5 < M(_bj) < -21.5, and cross-correlate them with 2SLAQ (z ≈ 0.5) and AAOmega (z ≈ 0.7) photometric and spectroscopic LRGs in the same redshift ranges. The 2-D and 3-D cross-clustering measurements are generally in good agreement. Our (2SLAQ) QSO-LRG clustering amplitude (r(_0) = 6.8 (^+0.1_-0.3)h(^-1)Mpc) as measured from the semi-projected cross-correlation function appears similar to the (2SLAQ) LRG-LRG auto-correlation amplitude (r(_0) = 7.45 ± 0.35h(^-1)Mpc) and both are higher than the (2QZ-t-2SLAQ) QSO-QSO amplitude (r(_0) ≈ 5.0h(^-1)Mpc). Our measurements show remarkably little QSO-LRG cross- clustering dependence on QSO luminosity. Assuming a standard ACDM model and values for b(_LRG) measured from LRG autocorrelation analyses, we find b(_Q) = 1.45 ± 0.11 at M(_bj) ≈ -24 and b(_Q) = 1.90 ± 0.16 at M(_bj) ≈ -22. We also find consistent results for the QSO bias from a z-space distortion analysis of the QSO-LRG cross-clustering at z ≈ 0.55. The velocity dispersions fitted to QSO-LRG cross-correlation, ع (σ,π), at 680 kms(^-1) are intermediate between those for QSO-QSO and LRG-LRG clustering, as expected given the larger QSO redshift errors. The dynamical infall results give ẞ(_Q) = 0.55 ± 0.10, implying b(_Q) = 1.4 ± 0.2. Thus both the z-space distortion and the amplitude analyses yield b(_Q) ≈ 1.5 at M(_bj) ≈ -23. The implied dark matter halo mass inhabited by QSOs at z ≈ 0.55 is ~ 10(^13)h(^-1)M(_ʘ), again approximately independent of QSO luminosity. Prompted by the indications from QSO lensing that there may be more mass associated with galaxy groups than expected from virial analyses, we make new dynamical infall estimates of the masses associated with 2PIGG groups and clusters. We analyse the redshift distortions in the cluster-galaxy cross-correlation function as a function of cluster membership, cross-correlating z < 0.12 2PIGG clusters and groups with the full 2dF galaxy catalogue. We make estimates of the dynamical infall parameter, ẞ, and new estimates of the group velocity dispersions for group membership classes out to z < 0.12. We first find that, out to 30-40h(^-1)Mpc, the amplitude of the full 3-D redshift space cross-correlation function, ع (_cg), rises monotonically with group membership. We use a simple linear-theory infall model to fit ع (σ,π), in the range 5 < s < 40h(^-1) Mpc. We find that the ẞ versus membership relation for the data shows a minimum at intermediate group membership n ≈ 20 or L ≈ 2 x l0(^11)h(^-2)L(_ʘ), implying that the bias and hence M/L ratios rise by a significant factor (≈ 5x) both for small groups and rich clusters. The minimum for the mocks is at a 2 - 3x lower luminosity than for the data. However, the mocks also show a systematic shift between the location of the ẞ minimum and the M/L minimum at L ≈ l0(^11)h(^-2)L(_ʘ), given by direct calculation using the known DM distribution. Our overall conclusion is that bias estimates from dynamical infall appear to support the minimum in star-formation efficiency at intermediate halo masses. Nevertheless, there may still be significant systematic problems arising from measuring ẞ x (^1/_b) ∂P(_mass) /∂P(_gaiaxies) using large-scale infall rather than M/L using small-scale velocity dispersions

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Buttery, H. J. "New methods for detecting high-redshift clusters of galaxies." Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597196.

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The detection of high-redshift clusters of galaxies is important in under-standing the evolution of our Universe. Computer simulations, assuming hierarchical structure formation within a Ω_λ » 0.7, Ω_M » 0.3 universe, predict the galaxy clusters should be detected out to redshifts of z = 1. Traditional methods for finding clusters of galaxies, for example using optical plates, are not well to cluster detection beyond a redshift of z = 0.3, because they suffer from contamination of foreground sources. A new method of searching for galaxy clusters has been devised. It uses the hypothesis that at high redshifts radiosources trace high-density regions of our Universe. This would imply that high-redshift groupings of radiosources would be preferentially found in the high-density environments of galaxy clusters. I have used the Sydney University Molonglo Sky Survey (SUMSS) to search for groupings of five radiosources within a seven-arcminute circle. In this thesis I present the work extracting 60 cluster candidates from SUMSS. I also present the radio, infrared and optical follow-up observations that were undertaken and the implications of these. This thesis also discusses the Sunyaev Zel’dovich Effect (SZE), which is the inverse-Compton scattering of the Cosmic Microwave Background (CMB) by a plasma. This is another new method for detecting high-redshift clusters of galaxies. It is particularly important because the magnitude of the effect is independent of redshift. I include the observations of a galaxy cluster where this effect is apparent carried out at the Ryle Telescope (RT) in Cambridge.

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Дисертації з теми "Galaxies : à haute redshift"

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