Universiẗat, Diss., 2002--Heidelberg.

University, Diss., 2005--Heidelberg.

L'objet de cette thèse est le spectre de puissance à une dimension du flux transmis dans les forêts Lyman-alpha. Les forêts Lyman-alpha sont un motif d'absorption observé dans les spectres de quasars correspondant à l'absorption de la lumière du quasar par les nuages d'hydrogène le long de la ligne de visée. C'est un outil cosmologique puissant car il sonde des échelles relativement petites de l'ordre de quelques Mpc. Il est aussi sensible à de petits effets non-linéaires tel que celui produit par des neutrinos massifs.Premièrement, nous avons développé deux méthodes indépendantes pour mesurer le spectre de puissance. La première est fondée sur une transformée de Fourier et la seconde sur une fonction de vraisemblance. Les deux méthodes sont indépendantes et ont des incertitudes systématiques différentes. La détermination du niveau de bruit dans les données spectrales a fait l'objet d'un traitement particulier, du fait de son impact significatif sur le spectre de puissance calculé. Nous avons appliqué ces méthodes à 13821 spectres de quasars provenant de la 9e publication de données de l'expérience BOSS sélectionnés à partir d'un échantillon de plus de 60000 spectres sur des critères comme le rapport signal sur bruit et la résolution spectrale. Les deux spectres de puissance mesurés sont en bon accord sur les douze domaines de décalage vers le rouge (<z>=2.2 à <z>=4.4) et sur l'ensemble des échelles (0.001 (km/s)^−1 à 0.02 (km/s)^−1). Nous avons soigneusement déterminé les incertitudes systématiques d'origine instrumentale et méthodologique de notre mesure.Ensuite, nous présentons un ensemble de simulations cosmologiques N-corps incluant de la matière noire, du gaz baryonique et des neutrinos visant à modéliser les régions de basse densité sondées par les forêts Lyman-alpha. Les simulations sont conçues pour répondre aux exigences de précision des données BOSS et eBOSS. Elles comportent 768^3 ou 192^3 particules de chaque type et explorent des volumes allant de (25 Mpc/h)^3 pour les simulations haute résolution à (100 Mpc/h)^3 pour les simulations grand volume. En utilisant une technique de raboutage, nous atteignons une précision équivalente à une simulation comportant 3072^3 particules de chaque type dans un volume de (100 Mpc/h)^3. Nous montrons que cette technique est précise à 2% sur des échelles allant de quelques Mpc jusqu'à quelques dizaines de Mpc. Nous explorons l'effet sur le spectre de puissance de 4 paramètres cosmologiques (n_s, sigma_8, Omega_m ,H_0), 2 paramètres astrophysiques (T_0, gamma) décrivant la relation température/densité du milieu intergalactique et de la somme des masses des neutrinos. En faisant varier ces paramètres autour d'un modèle central choisi en accord avec les résultats de Planck, nous avons construit une grille de simulations, permettant non seulement l'étude de l'effet de chaque paramètre individuellement mais aussi l'effet de chaque paire de paramètres. Nous obtenons ainsi un développement au deuxième ordre complet, incluant les termes croisés, autour de notre modèle central. Nous avons vérifié la validité de ce développement avec des simulations indépendantes obtenues soit avec des paramètres différents soit une graine différente pour la génération des conditions initiales. Une comparaison entre le spectre de puissance mesuré à partir des données dans la première partie et celui obtenu à partir de nos simulations montre un excellent accord.Enfin, même s'il reste des biais potentiels et des erreurs systématiques à étudier dans nos simulations, nous avons réalisé des ajustements en combinant notre mesure du spectre de puissance à d'autres sondes cosmologiques comme les mesures du fond diffus cosmologique par le satellite Planck. Ces résultats préliminaires sont très encourageants car ils mènent à des contraintes sur les paramètres cosmologiques parmi les plus précises à ce jour, en particulier sur la sommes des masses des neutrinos avec une limite supérieure à 0.1 ev. / The framework of the studies presented in this thesis is the one-dimensional power spectrum of the transmitted flux in the Lyman-alpha forests. The Lyman-alpha forest is an an absorption pattern seen in the spectra of high redshift quasars corresponding to the absorption of the quasar light by the hydrogen clouds along the line of sight. It is a powerful cosmological tool as it probes relatively small scales, of the order of a few Mpc. It is also sensible to small non-linear effects such as the one induced by massive neutrinos.First, we have developed two independent methods to measure the one-dimensional power spectrum of the transmitted flux in the Lyman-alpha forest. The first method is based on a Fourier transform, and the second on a maximum likelihood estimator. The two methods are independent and have different systematic uncertainties. The determination of the noise level in the data spectra was subject to a novel treatment, because of its significant impact on the derived power spectrum. We applied the two methods to 13,821 quasar spectra from SDSS-III/BOSS DR9 selected from a larger sample of over 60,000 spectra on the basis of their high quality, large signal-to-noise ratio, and good spectral resolution. The power spectra measured using either approach are in good agreement over all twelve redshift bins from <z>=2.2 to <z>=4.4, and scales from 0.001 (km/s)^−1 to 0.02 (km/s)^−1. We carefully determined the methodological and instrumental systematic uncertainties of our measurements.Then, we present a suite of cosmological N-body simulations with cold dark matter, baryons and neutrinos aiming at modeling the low-density regions of the IGM as probed by the Lyman-alpha forests at high redshift. The simulations are designed to match the requirements imposed by the quality of BOSS and eBOSS data. They are made using either 768^3 or 192^3 particles of each type, spanning volumes ranging from (25 Mpc/h)^3 for high-resolution simulations to (100 Mpc/h)^3 for large-volume ones. Using a splicing technique, the resolution is further enhanced to reach the equivalent of simulations with 3072^3 = 29 billion particles of each type in a (100 Mpc/h)^3 box size, i.e. a mean mass per gas particle of 1.2x10^5 solar masses. We show that the resulting power spectrum is accurate at the 2% level over the full range from a few Mpc to several tens of Mpc. We explore the effect on the one-dimensional transmitted-flux power spectrum of 4 cosmological parameters (n_s, sigma_8, Omega_m ,H_0), 2 astrophysical parameters (T_0, gamma) related to the heating rate of the IGM and the sum of the neutrino masses. By varying the input parameters around a central model chosen to be in agreement with the latest Planck results, we built a grid of simulations that allows the study of the impact on the flux power spectrum of these seven relevant parameters. We improve upon previous studies by not only measuring the effect of each parameter individually, but also probing the impact of the simultaneous variation of each pair of parameters. We thus provide a full second-order expansion, including cross-terms, around our central model. We check the validity of the second-order expansion with independent simulations obtained either with different cosmological parameters or different seeds for the initial condition generation. Finally, a comparison to the one-dimensional Lyman-alpha forest power spectrum obtained in the first part with BOSS data shows an excellent agreement.Eventually, even if there are still some potential biases and systematic errors that need to be studied in our simulation, we performed cosmological fits combining our measurement of the one-dimensional power spectrum and other cosmological probes such as the CMB results provided by Planck. These preliminary results are very encouraging as they lead to some of the tighest cosmological constraints as of today, especially on the sum of the neutrino masses with an upper limit of 0.1 eV.

Cosmic reionization was most likely initiated by star forming dwarf galaxies. Little is known about the physical mechanisms allowing ionizing Lyman continuum (LyC) photons to escape from galaxies, but to learn more we can study local galaxies in detail. Until now, there has however only been one claim of a local LyC leaking galaxy, the disputed case of Haro 11. The lack of local detections could in part be a combined effect of technical problems and search strategies. Re-examining the FUSE (Far Ultraviolet Spectroscopic Explorer) data of Haro 11 led us to develop a new model for the spectral reduction, by which we could confirm an escape fraction of LyC photons (fesc) of 3.3±0.7%. In addition, eight more galaxies from the FUSE archive were examined leading to a new detection, Tol 1247-232, with fesc = 2.4±0.5%. The low value derived from the stacked spectrum of the whole sample, fesc = 1.4±0.4%, could be an indication of an evolving fesc scenario and/or an effect of probing the wrong targets. Local LyC candidates are normally selected among starburst galaxies with high equivalent widths in Hα. This can however give preference to ionization bounded H II regions with low escape fractions. In an attempt to overcome this selection bias, we developed a novel method to select LyC leaking galaxies. The selection is based on a blue continuum and weak emission lines, properties that in combination can be explained only by models with very high fesc. Using these criteria, we selected a sample of leaking candidates at z≈0.03 to be observed in Hα and Johnson B filters. The sample galaxies have properties that strongly favour leakage. Among these are clear signs of mergers and interaction with neighbouring galaxies, off-centre major star forming regions and spectral properties indicating previous starburst activity. The Lyman-alpha (Lyα) line is often used as a tracer for the distant galaxies believed to have reionized the universe. Here, for the first time local face-on spiral galaxies are studied in Lyα imaging. All three galaxies are emitting Lyα photons in the polar direction far out in the spiral arms, in clear contrast to previously studied irregular galaxies where strong emission is seen from the nuclei. If the small sample studied here is representative, it will have implications for detecting Lyα galaxies at high redshifts as it would depend strongly on the viewing angle.

abstract: Galaxies with strong Lyman-alpha (Lya) emission line (also called Lya galaxies or emitters) offer an unique probe of the epoch of reionization - one of the important phases when most of the neutral hydrogen in the universe was ionized. In addition, Lya galaxies at high redshifts are a powerful tool to study low-mass galaxy formation. Since current observations suggest that the reionization is complete by redshift z~ 6, it is therefore necessary to discover galaxies at z > 6, to use their luminosity function (LF) as a probe of reionization. I found five z = 7.7 candidate Lya galaxies with line fluxes > 7x10-18 erg/s/cm/2 , from three different deep near-infrared (IR) narrowband (NB) imaging surveys in a volume > 4x104Mpc3. From the spectroscopic followup of four candidate galaxies, and with the current spectroscopic sensitivity, the detection of only the brightest candidate galaxy can be ruled out at 5 sigma level. Moreover, these observations successfully demonstrate that the sensitivity necessary for both, the NB imaging as well as the spectroscopic followup of z~ 8 Lya galaxies can be reached with the current instrumentation. While future, more sensitive spectroscopic observations are necessary, the observed Lya LF at z = 7.7 is consistent with z = 6.6 LF, suggesting that the intergalactic medium (IGM) is relatively ionized even at z = 7.7, with neutral fraction xHI&le; 30%. On the theoretical front, while several models of Lya emitters have been developed, the physical nature of Lya emitters is not yet completely known. Moreover, multi-parameter models and their complexities necessitates a simpler model. I have developed a simple, single-parameter model to populate dark mater halos with Lya emitters. The central tenet of this model, different from many of the earlier models, is that the star-formation rate (SFR), and hence the Lya luminosity, is proportional to the mass accretion rate rather than the total halo mass. This simple model is successful in reproducing many observable including LFs, stellar masses, SFRs, and clustering of Lya emitters from z~ 3 to z~ 7. Finally, using this model, I find that the mass accretion, and hence the star-formation in > 30% of Lya emitters at z~ 3 occur through major mergers, and this fraction increases to ~ 50% at z~7. / Dissertation/Thesis / Ph.D. Astrophysics 2011

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

Angular differential imaging provides a novel way of probing high contrast regions of our universe. Until now, its applications have been primarily localized to searching for exoplanets around nearby stars. This work presents a suite of applications of angular differential imaging from the theoretical underpinning of data reduction, to its use characterizing substellar objects, to a new application looking for the host galaxies of damped Lyman α systems which are usually lost in the glare of ultra-bright quasars along the line of sight. The search for exoplanets utilizes angular differential imaging and relies on complex algorithms to remove residual speckles and artifacts in the images. One such algorithm, the Template Locally Optimized Combination of Images (TLOCI), uses a least-squares method to maximize the signal-to-noise ratio and can be used with variable parameters, such as an input spectral template, matrix inversion method, aggressivity and unsharp mask size. Given the large volume of image sequences that need to be processed in any exoplanet survey, it is important to find a small set of parameters that can maximize detections for any conditions. Rigorous testing of these parameters were done with on-sky images and simulated inserted planets to find the optimal combination of parameters. Overall, a standard matrix inversion, along with two to three input templates, a modest aggressivity of 0.7 and the smallest unsharp mask was found to be the best choice to balance optimal detection. Beyond optimizations, TLOCI has been used in conjunction with angular differential imaging to characterize substellar objects in our local solar neighbourhood. In particular, the star HD 984 was imaged as a part of the Gemini Planet Imager Exoplanet Survey. Although previously known to have a substellar companion, new imaging presented here in the H and J bands help further characterize this object. Comparisons with a library of brown dwarf spectral types found a best match to HD 984 B of a type M7±2. Orbital fitting suggests an 18 AU (70 year) orbit, with a 68% confidence interval between 12 and 27 AU. Object magnitude was used to find the luminosity, mass and temperature using DUSTY models. Although angular differential imaging has proven its value in high contrast imaging, it has largely remained in the field of substellar object detection, despite other high contrast regimes in which it could be applied. One potential application is outside the local solar neighbourhood with studies of damped Lyman α systems, which have struggled to identify host galaxies thought to be caused by systems seen in the spectra of bright quasars. Work herein presents the first application of angular differential imaging to finding the host galaxies to damped Lyman α systems. Using ADI we identified three potential systems within 30kpc of the sightline of the quasar and demonstrate the potential for future imaging of galaxies at close separations. In summary, this thesis presents a comprehensive look at multiple aspects of high contrast angular differential imaging. It explores optimizations with a data reduction algorithm, implementations characterizing substellar objects, and new applications imaging galaxies. / Graduate

Environment is known to have a significant impact on the evolution of galaxies. This is most evident in the local Universe, where the oldest and most massive galaxies are found at the of massive galaxy clusters. Current theory predicts that galaxies will form earlier and evolve more rapidly in the densest regions of the Universe. What is not clear is how rapidly the of environment start to have an impact on galaxies, at what stage can we detect physical differences between galaxies in dense regions and those in the field? By the time galaxies are assembled in virialised clusters the effects are clear, but at higher redshift (z ≳ 2), in the unvirialised progenitors of clusters (protoclusters) the effects are harder to detect. In this thesis I study the impact of environment in a z =3.1 protocluster in the SSA22 field. I consider the fraction of mergers in the protocluster, comparing it to the fraction of mergers in field at a similar redshift. My classification is based on the morphology of Lyman break (LBGs), using HST ACS/F814W imaging, which probes the rest frame UV. I find a marginal enhancement of the merger fraction, 48±10 per cent for LBGs in the protocluster compared 30±6 per cent in the field, suggesting that galaxy-galaxy mergers are one of the key driving accelerated star formation and AGN growth in protocluster environments. Having considered the fraction of mergers in the protocluster I then turn my attention to the physical properties of LBGs. I use multiwavelength data and spectral energy distribution fitting to determine the mass of LBGs in the protocluster and in the field. I find no statistical evidence for an enhancement of mass in the protocluster, suggesting that the protocluster environment has not impacted the average mass of LBGs at this redshift. It is possible that the protocluster LBG population may become more massive than LBGs in the field at lower redshift, or the galaxies may cease to be detectable by the Lyman break method before a mass difference between the protocluster galaxies and field is observable. Finally I consider the Lyman-α blobs (LABs) within the protocluster. These are large (~10- 100kpc) scale regions of diffuse Lyman-α emission, thought to be associated with overdense regions. 35 LABs have been detected in the SSA22 protocluster, indicating the presence of large clouds of gas in the circumgalactic medium. A debate has arisen regarding the powering mechanism of the LABs, particularly between star forming processes (e.g. Lyman-α escaping from a star forming galaxy or photoionizing radiation escaping from a star forming galaxy or active galactic nuclei) and a cold accretion model. The latter involves gas gravitationally cooling as it falls into the centre of a dark matter halo to feed a central galaxy. Some of this energy heats the cold gas, which then emits Lyman-α as it cools. The cold gas accretion theory gained popularity because some LABs appear not to contain a luminous galaxy or AGN which could explain the observed emission. One suggestion is that the central galaxy could be hidden by dust and that this could explain the lack of a detection in UV or optical. I therefore use SCUBA2 850μm imaging to search for submm sources (dusty star forming galaxies) in the LABs. I detect submm sources in only two of the LABs at 3.5δ, however, stacking all the LABs gives an average flux density of S850 = 0.6±0.2mJy. This suggests that on average the LABs do contain a submm source which could be a dusty galaxy. However, stacking the LABs by size indicates that only the largest third (area ≳ 1800kpc²) have a mean detection, at 4.5δ, with S850 = 1.4±0.3mJy, suggesting that different mechanisms may dominate the larger and smaller LAB populations. I explore two possible mechanisms for powering the LABs, cold accretion and central star forming galaxies. I find that central star formation is more likely to be the dominant source of emission, with cold accretion playing a secondary role.

To constrain the era when the first galaxies and stars appeared upcoming instruments will rely on the brightest events in the universe: supernovae and brilliant emission from massive black holes. In this dissertation, we investigate the observability of certain types of supernovae of the very first stars (Population III stars) and find that while these events are sufficiently luminous to be observed with deep-sky instruments such as the James Webb Space Telescope (JWST), they may not observe these particular types of events in their lifetimes. We next explore the origins of massive black holes and introduce the direct collapse hypothesis of supermassive black hole formation. We model CR7, an apparently metal-free, luminous, Lyman-alpha emitting galaxy, as if it were powered by a massive direct collapse black hole and find that such a black hole can account for CR7's impressive Lyman-alpha flux. We finally investigate the nature of the connection between water megamasers, very bright radio sources originating from population inversion in dense, shocked gas around massive black holes and hydroxyl megamasers which generally accompany star formation. We carry out a ~ 60 hour radio survey for water emission among galaxies hosting OH megamaser hosts to assess the connection between the two types of emission. We find marginally statistically significant evidence that OH megamasers exclude water kilomasers and confirm with high levels of significance (> 8 sigma) the presence of a water megamaser in II Zw 96, establishing this object as the second galaxy known to cohost simultaneous water and hydroxyl megamasers.

Strong damped Lyman alpha absorption (DLA) lines seen spectra of distant quasar are believed to arise when the sight line to the quasar goes trough the disc of a galaxy or a proto galaxy. Most of the neutral matter in the universe is contained in these clouds of neutral hydrogen that cause the absorption lines. Hence these DLAs are reservoirs for the formation of stars and galaxies throughout the universe. Despite intensive efforts over more than two decades only few galaxies responsible for the DLAs have been found. The problem is that the galaxies that harbour the neutral clouds are not necessarily bright, and selecting galaxies based on absorption lines could well select different types of galaxies than found in large surveys. If we are to understand how galaxies form out of neutral gas clouds it is essential to locate the galaxies in which DLAs reside. <br><br> This thesis explores the use of integral field spectroscopy (IFS) to observe quasars known to have strong absorption lines in their spectra. IFS allows us to obtain a spectrum at many spatial points close to the quasar, thus providing images and spectroscopy simultaneously. From the imaging part, we can directly identify objects, and from the spectroscopy we can calculate the distances to the objects. When the distance of the object found in emission matches the distance to the object that cause the DLA line, we have identified the absorbing galaxy. <br><br> Using this technique, we have showed that we can successfully recover a few DLA galaxies known previously from the literature. In a survey aimed to increase the number of DLA galaxies we have identified eight new candidate DLA galaxies. The projected distances from the candidates to the quasar sight lines indicate that the DLA galaxies have sizes similar to local disc galaxies. Hence our results suggest that large discs may be present when the universe was just 2 billion years old. We furthermore find no differences between the sizes of the very distant DLA galaxies and those that are not so distant. The large sizes imply that their neutral hydrogen masses are also similar to those in local galaxies, but we argue that the DLA galaxies are not necessarily as luminous as the present day disc galaxies. <br><br> Taking advantage of the three-dimensional view provided by the IFS data, the second part of this thesis investigates extended emission line regions arising in the quasar neighborhood. We find that extended emission line nebulae are common around quasars, and explore the effects that may be the cause. Some quasars are known to be powerful radio emitters while others are not detected at radio wavelengths. We find that significantly larger and brighter emission line nebulae are found around the quasars which have the brightest radio emission, and in particular those that have large radio jets. The existence of the nebulae can be interpreted as an interaction of the radio jet with the surrounding medium, but we can not rule out a scenario where there are density or temperature differences in the surrounding environment. Only for the brightest object, where additional velocity information can be derived from the IFS data, can we argue for an interaction. <br><br> In conclusion the use of IFS to search for faint emission lines, both from point sources and extended nebulae provides exciting new results within the scientific areas studied here. / Man glaubt, daß starke gedämpfte Lyman alpha Absorptionslinien (damped Lyman alpha lines, DLA lines) in den Spektren entfernter Quasare entstehen, wenn die Sichtlinie zu dem Quasar durch eine Galaxie oder eine Proto-Galaxie geht. Die meiste neutrale Materie des Universums ist in diesen Wolken aus neutralem Wasserstoff enthalten, die die Absorptionslinien verursachen. Daher sind diese DLAs Reservoire für die Bildung von Sternen und Galaxien im gesamten Universum. Trotz intensiver Anstrengungen seit mehr als zwei Jahrzehnten konnten nur wenige Galaxien gefunden werden, die für DLAs verantwortlich sind. Das Problem ist, daß die Galaxien, die die neutralen Wolken beherbergen, nicht notwendigerweise hell sind, und Galaxien basierend auf Absorptionslinien zu selektieren, könnte leicht andere Typen von Galaxien selektieren, als diejenigen, die in großen Durchmusterungen gefunden werden. Wenn wir verstehen wollen wie Galaxien aus neutralen Gaswolken entstehen, ist es entscheidend, die Galaxien ausfindig zu machen, in denen DLAs liegen. <br><br> Diese Doktorarbeit erforscht die Nutzung der Ganzfeldspektroskopie (integral field spectroscopy, IFS), um Quasare zu beobachten, die bekanntermaßen starke Absorptionslinien in ihren Spektren haben. IFS erlaubt uns, ein Spektrum an vielen räumlichen Punkten nahe des Quasars zu erhalten, somit Bilder und Spekroskopie gleichzeitig zu liefern. Aus den Bildern können wir direkt Objekte identifizieren und aus der Spektroskopie können wir die Entfernungen zu den Objekten berechnen. Wenn die Entfernung zum gefundenen Objekt mit der Entfernung zu einer DLA-Linie übereinstimmt, dann haben wir die absorbierende Galaxie gefunden. <br><br> Diese Methode anwendend, können wir zeigen, daß wir erfolgreich einige wenige schon aus der Literatur bekannte DLA-Galaxien wiederentdecken können. In einer auf Erhöhung der Zahl von DLA-Galaxien abzielenden Duchmusterung haben wir acht neue DLA-Galaxienkandidaten identifiziert. Die projizierten Entfernungen von den Kandidaten zu den Quasarsichtlinien lassen erkennen, daß die DLA-Galaxien ähnliche Größen haben, wie nahe Scheibengalaxien. Daher lassen unsere Resultate darauf schließen, daß es große Scheibengalaxien gegeben haben könnte, als das Universum gerade zwei Milliarden Jahre alt war. Außerdem finden wir keine Unterschiede zwischen den Größen der sehr weit entfernten DLA-Galaxien und jenen, die nicht so weit entfernt sind. Die Größen implizieren, daß ihre Massen gebunden in neutralem Wasserstoff auch ähnlich sind zu jenen in lokalen Galaxien, aber wir vertreten die Ansicht, daß DLA-Galaxien nicht notwendigerweise so leuchtkräftig sind wie heutige Scheibengalaxien. <br><br> Den dreidimensionalen Blick ermöglicht durch die IFS-Daten ausnutzend, untersucht der zweite Teil dieser Doktorarbeit ausgedehnte Emissionslinienregionen, die in der Nachbarschaft der Quasare entstehen. Wir finden heraus, daß ausgedehnte Emissionsliniennebel um Quasare häufig sind und erforschen die ihnen zugrundeliegenden Effekte. Einige Quasare sind bekannte starke Radioquellen, während andere nicht im Radiobereich entdeckt werden. Wir zeigen, daß bedeutend größere und hellere Emissionsliniennebel um Quasare gefunden werden, welche die stärkste Radioemission, insbesondere große Radiojets, aufweisen. Die Existenz der Nebel kann interpretiert werden als eine Wechselwirkung der Radiojets mit dem umgebenden Medium, aber wir können nicht ausschließen, daß es Dichte- oder Temperaturunterschiede in der Umgebung gibt. Nur für die hellsten Objekte, für die zusätzliche Geschwindigkeitsinformation aus den IFS-Daten abgeleitet werden kann, vertreten wir die Ansicht der Wechselwirkung. <br><br> Die Nutzung der IFS bei der Suche nach schwachen Emissionslinien von Punktquellen wie auch ausgedehnten Nebeln bietet spannende neue Ergebnisse in den hier studierten wissenschaftlichen Gebieten.