Dissertations / Theses on the topic 'Galaxy evolution'
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Croton, Darren. "Galaxy Formation and Evolution." Diss., lmu, 2005. http://nbn-resolving.de/urn:nbn:de:bvb:19-44059.
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Ruggiero, Rafael. "Galaxy Evolution in Clusters." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/14/14131/tde-14022019-140755/.
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In this thesis, we aim to further elucidate the phenomenon of galaxy evolution in the environment of galaxy clusters using the methodology of numerical simulations. For that, we have developed hydrodynamic models in which idealized gas-rich galaxies move within the ICM of idealized galaxy clusters, allowing us to probe in a detailed and controlled manner their evolution in this extreme environment. The main code used in our simulations is RAMSES, and our results concern the changes in gas composition, star formation rate, luminosity and color of infalling galaxies. Additionally to processes taking place inside the galaxies themselves, we have also described the dynamics of the gas that is stripped from those galaxies with unprecedented resolution for simulations of this nature (122 pc in a box including an entire 1e14 Msun cluster), finding that clumps of molecular gas are formed within the tails of ram pressure stripped galaxies, which proceed to live in isolation within the ICM of a galaxy cluster for up to 300 Myr. Those molecular clumps possibly represent a new class of objects; similar objects have been observed in both galaxy clusters and groups, but no comprehensive description of them has been given until now. We additionally create a hydrodynamic model for the A901/2 multi-cluster system, and correlate the gas conditions in this model to the locations of a sample of candidate jellyfish galaxies in the system; this has allowed us to infer a possible mechanism for the generation of jellyfish morphologies in galaxy cluster collisions in general.Nesta tese, nós visamos a contribuir para o entendimento do fenômeno da evolução de galáxias no ambiente de aglomerados de galáxias usando a metodologia de simulações numéricas. Para isso, desenvolvemos modelos hidrodinâmicos nos quais galáxias idealizadas ricas em gás movem-se em meio ao gás difuso de aglomerados de galáxias idealizados, permitindo um estudo detalhado e controlado da evolução destas galáxias neste ambiente extremo. O principal código usado em nossas simulações é o RAMSES, e nossos resultados tratam das mudanças em composição do gás, taxa de formação estelar, luminosidade e cor de galáxias caindo em aglomerados. Adicionalmente a processos acontecendo dentro das próprias galáxias, nós também descrevemos a dinâmica do gás que é varrido dessas galáxias com resolução sem precedentes para simulações dessa natureza (122 pc em uma caixa incluindo um aglomerado de 1e14 Msun inteiro), encontrando que aglomerados de gás molecular são formados nas caudas de galáxias que passaram por varrimento de gás por pressão de arraste, aglomerados estes que procedem a viver em isolamento em meio ao gás difuso de um aglomerado de galáxias por até 300 Myr. Esses aglomerados moleculares possivelmente representam uma nova classe de objetos; objetos similares foram previamente observados tanto em aglomerados quanto em grupos de galáxias, mas um tratamento compreensivo deles não foi apresentado até agora. Nós adicionalmente criamos um modelo hidrodinâmico para o sistema multi-aglomerado A901/2, e correlacionamos as condições do gás nesse modelo com a localização de uma amostra de galáxias jellyfish nesse sistema; isso nos permitiu inferir um possível mecanismo para a geração de morfologias jellyfish em colisões de aglomerados de galáxias em geral.
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Curtis, Lake Emma. "Galaxy evolution with FMOS." Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:866b8ba5-5353-43a7-9898-a4b767ab0f6d.
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This thesis is concerned with the targeting of emission line galaxies with FMOS (Fibre Multi-Object Spectrograph) to determine properties of star forming galaxies at redshift ~1.5, and provide measurements of the growth rate of large-scale structure through Redshift Space Distortions (RSDs). I also consider the opportunities of targeting the passive galaxy population at high redshift, through measurements of their continuum. I start with the extensive broad-band photometric data available in the UKIDSS-UDS (United Kingdom Infrared Telescope Deep Sky Survey - Ultra-Deep Survey) field which is used to produce a band-merged catalogue, later used for determining photometric redshifts. In producing this catalogue, I approach the issue of source confusion present in the deep Spitzer imaging using z-band priors on profile position and shape and an iterative Expectation-Maximisation algorithm. Photometric redshift estimates are compared against colour selections as potential targeting techniques for a wide-area redshift survey with FMOS. Different photometry survey areas are considered, and the quality of selection given the available broad-band data tested, by adjusting the photometric catalogue produced for the UDS. The results indicate that the SWIRE (Spitzer Wide area InfraRed Extragalactic Survey) fields are too small to provide adequate sources with a consistent selection mechanism. The CFHTLS (Canada-Frace-Hawaii Telescope Legacy Survey) would have a large enough area given deeper z'-band imaging, and SWIRE-depth coverage in the Spitzer 3.6μm and 4.5μm bands. I present FMOS commissioning data obtained for the UDS field, including the spectroscopic targeting of sources form the High-Z Emission Line Survey (HiZELS). With this data, I am able to test the current quality of flux calibration using cool stars targeted simultaneously and the level of systematic errors left by sky-subtraction. The sample of HiZELS sources selected to place Hα at z~1.45 show low contamination from other emission lines, and only one out of 9 targets assigned a redshift has any indication of AGN activity. Finally, I present longslit observations of faint, passive galaxies at redshift z~1.9, selected as members of a possible cluster, JKCS 041, selected from broad band colours. One object was observed with high enough signal to noise to constrain the position of the 4000 Å / Balmer break, providing a tighter constraint on the photometric redshift of 1.8867 +0.0034 -0.0117.
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Linke, Laila Maria [Verfasser]. "Testing models of galaxy formation and evolution with galaxy-galaxy-galaxy lensing / Laila Maria Linke." Bonn : Universitäts- und Landesbibliothek Bonn, 2021. http://d-nb.info/1235524469/34.
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Martinet, Nicolas. "Galaxy clusters : a probe to galaxy evolution and cosmology." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066348/document.
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Cette thèse présente un certain nombre de résultats récents à propos de l'évolution des galaxies et la cosmologie, à partir de l'observation d'amas de galaxies en lumière visible. Nous introduisons d'abord les principales propriétés des amas de galaxies (Chapitre 1.1) et la façon dont ces objets permettent de contraindre le modèle cosmologique standard (Chapitre 1.2). Une grande partie des résultats présentés ici ont été obtenus à partir de l'étude du relevé d'amas DAFT/FADA, qui regroupe des amas dans la gamme de décalages spectraux 0.4This thesis presents some recent results concerning galaxy evolution and cosmology,based on the observation of galaxy clusters at optical wavelengths. We first introduce the main properties of galaxy clusters (Sect. 1.1) and how they can be used for cosmology within the standard cosmological model (Sect. 1.2). A large fraction of the presented results comes from the study of the DAFT/FADA galaxy cluster survey at redshifts 0.4 < z < 0.9 (Sect. 1.3). We divide our study in two parts according to the observable that is considered: galaxy luminosity or galaxy shape. The distribution of galaxy luminosities is called the galaxy luminosity function (GLF), which can be used to probe the evolution of cluster galaxies (Sect. 2.1). Computing the GLFs for a sub sample of 25 DAFT/FADA clusters, we find that faint blue star forming galaxies are quenched into red quiescent galaxies from high redshift until today. Comparing to the field shows that this transformation is more efficient in high density environments.We also study the fraction of baryons in galaxy groups and clusters (Sect. 2.2). Wefind that in groups, the stars contained in galaxies can reach masses of the same order as those of the intra-cluster gas, while in clusters they are usually negligible relatively to the gas. Taking both stars and gas into account we constrain the matter density parameter Galaxy shapes are distorted by foreground objects that bend light in their vicinity. This lensing signal can be exploited to measure the mass distribution of a foreground cluster. We review the basic theory of weak lensing and shear measurement (Sect. 3.1), and then apply it to a subsample of 16 DAFT/FADA clusters, with Subaru/SuprimeCam or CFHT/MegaCam imaging (Sect. 3.2). We estimate the masses of these clusters, and take advantage of the large fields of view of our images to detect filaments and structures in the cluster vicinity, observationally supporting the hierarchical scenario of cluster growth. Finally, we detect shear peaks in Euclid-like simulations, and use their statistics as a cosmological probe, similarly to cluster counts (Sect. 3.3). We forecast the cosmological constraints that this technique will achieve when applied to the Euclid space mission, and develop a tomographic analysis that adds information from redshifts. We conclude with a discussion of our perspectives on future studies in all the fieldsinvestigated in the present thesis
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Cool, Richard Jacob. "Empirical Measurements of Massive Galaxy and Active Galaxy Evolution." Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/195540.
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Using new wide-area galaxy redshift surveys, we explore the evolutionof the most massive galaxies and the most luminous quasars in the universe over much of cosmic history. Quasars and massive red galaxies both areextremes; the most luminous high redshift quasars likely play a key role in shaping their nearby environment and the universe as a whole. The mostmassive galaxies represent the end points of galaxy evolution and containa fossil record of the galaxy evolution process.Using the AGES redshift survey completed with the MMT and the Hectospecmulti-object spectrograph as well as new $z$-band observations of the NOAO Deep Wide-Field Survey Bootes field, we report the discovery of threenew quasars at z>5. We explore new mid-infrared selection in light of thesethree new quasars and place constraints on the slope of the high-redshiftquasar luminosity function.At lower redshift (0.1
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Thomas, Daniel. "Chemical evolution and galaxy formation." Diss., lmu, 2000. http://nbn-resolving.de/urn:nbn:de:bvb:19-4637.
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Bothwell, Matthew Stuart. "Galaxy evolution : near and far." Thesis, University of Cambridge, 2011. https://www.repository.cam.ac.uk/handle/1810/265602.
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The formation of stars from interstellar gas is the cornerstone of galaxy evolution. This thesis represents work undertaken in order to characterise the role of cool interstellar gas, and its relation to star formation, in galaxy evolution across cosmic time. In particular, it concentrates on star forming galaxies at the extremes of the galaxy assembly spectrum - extremely faint dwarfs, and extremely luminous starbursts - in an attempt to test the limits of galaxy evolution models. The thesis falls into two complimentary halves, addressing topics in the low redshift and high redshift Universe respectively. In the low redshift Universe, I discuss multi-wavelength studies of large samples of z rv O galaxies, which include extremely faint dwarf galaxies in the Local Volume. Using these samples, it is possible to derive a multitude of physical parameters (including star formation rates, stellar masses, and gas masses) which allow the interrelationship between star formation and gas content to be assessed in a statistically significant manner. In particular, modern wide field surveys (combined with deep, volume-limited data) allow trends to be analysed across many orders of magnitude in galaxy mass and star formation rate, shedding light on the global properties of galaxies in the local Universe. Moving to higher redshift, I discuss targeted observations of molecular gas in extreme star forming galaxies in the early Universe. These 'sub-millimetre' galaxies number amongst the most luminous objects ever discovered, and molecular gas observations have the power to uncover many of their physical properties, including their morphologies, kinematics, and star formation behaviour. I begin by presenting high-resolution observations of a small number of these galaxies at z rv 2, and discussing the implications for galaxy evolution studies. The final chapter of this thesis consists of the results of a survey for molecular gas in sub-millimetre galaxies conducted over the last decade, which represents the largest single study of molecular gas in the early Universe to date.
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Moustakas, John. "Spectral Diagnostics of Galaxy Evolution." Diss., The University of Arizona, 2006. http://hdl.handle.net/10150/305142.
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Despite considerable progress in recent years, a complete description of the physical drivers of galaxy formation and evolution remains elusive, in part because of our poor understanding of star formation, and how star formation in galaxies is regulated by feedback from supernovae and massive stellar winds. Insight into the star formation histories of galaxies, and the interplay between star formation and feedback, can be gained by measuring their chemical abundances, which until recently has only been possible for galaxies in the nearby universe. However, reliable star formation and abundance calibrations have been hampered by various systematic uncertainties, and the lack of a suitable spectrophotometric sample with which to develop better calibrations. To address the limitations of existing surveys, we have obtained integrated optical spectra for a diverse sample of more than four hundred nearby star-forming galaxies. Using these data, in conjunction with observations from the Sloan Digital Sky Survey, we conduct a detailed analysis of optical star formation indicators, and develop empirical calibrations for the [O II] 3727 and H-beta 4861 nebular emission lines. Next, we investigate whether integrated spectroscopy of star forming galaxies can be used to infer their gas-phase oxygen abundances in the presence of radial abundance gradients, diffuse-ionized gas emission, and dust attenuation. We conclude that the integrated R23 parameter is generally insensitive to these systematic effects, enabling the gas-phase metallicity to be measured with a precision of +/-0.1 dex. We apply these methods to study the evolution in the luminosity-metallicity relation at 0
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Osmond, John Peter Francis. "The evolution of galaxy groups." Thesis, University of Birmingham, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.422727.
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Shabala, Stanislav. "AGN feedback in galaxy evolution." Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612309.
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Davidge, Helen. "Probing galaxy evolution with AKARI." Thesis, Open University, 2017. http://oro.open.ac.uk/49554/.
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This thesis presents the first detailed analysis of three extragalactic fields observed by the infrared satellite, AKARI. AKARI is the only telescope able to observe deeply in the Spitzer/IRAC - Spitzer/MIPS band gap of 8-24 microns. The first analysis of these extragalactic fields, was to perform galaxy number counts, the most basic statistical property of galaxy populations. Presented are the counts at 3, 4, 7, 11, 15 and 18 microns. These number counts were compared with published results and galaxy evolution models. These models are dependent on both the Spectral Energy Distribution (SED) templates and evolution of the galaxy types. The phenomenological backwards evolution model of Pearson 2005 appeared to be consistent with the number counts. To probe this, number counts were extracted from below the survey limit by performing Probability of Deflection (P(D)) fluctuation analysis. The Pearson model was found to be consistent with the 11 microns P(D) analysis but not with the 15 microns. The results from the 15 microns P(D) analysis indicates that the Pearson model under predicts the evolution of star forming galaxies. Multi-wavelength band-merged catalogues for the two deep extragalactic fields were created using AKARI data from the work of this thesis and ancillary data. The separation of galaxy type using AKARI/IRC filter colours was explored. For z < 2 a separation criteria was found for Active Galactic Nuclei (AGN), but to accurately classify galaxy type, SED fitting is required. Submm-selected galaxies detected by AKARI were found to resemble scaled-up normal local spiral galaxies, rather than starbursts, consistent with them lying on the high-redshift `main sequence' unlike local ultraluminous infrared galaxies. The thesis concludes by measuring the percentage of the far-infrared Cosmic Infrared Background (CIB) resolved by AKARI mid-infrared galaxies. By performing stacking analysis on a Herschel/SPIRE 250 microns image of AKARI galaxy positions, it was found that AKARI mid-infrared galaxies resolve ~10% of the 250 micron CIB.
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Romano, Donatella. "Chemical evolution and galaxy formation." Doctoral thesis, SISSA, 2002. http://hdl.handle.net/20.500.11767/4041.
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Following a review of the basic ingredients necessary for constructing models
of galactic chemical evolution, with a special emphasis on the issue of stellar
evolution and nucleosynthesis (which is treated in detail in Chapter 2), I continue
with the basic equations that one needs to solve in order to follow the chemical
evolution of a system of gas and stars in time and space.
The assumptions of the models I have handled with the aim of addressing different
aspects of the formation and evolution of the Milky Way and elliptical galaxies
are discussed in Chapter 3.
In Chapters 4 and 5, I present the results of my own research, mainly focusing
on how important is the analysis of the chemical abundances and especially abundance
ratios in galaxies for understanding their formation and evolution, in spite of
the many parameters involved in the modelling.
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Thomas, Nicole. "Galaxy Clustering as a Probe for Galaxy Evolution in Simulations." University of the Western Cape, 2017. http://hdl.handle.net/11394/6206.
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Magister Scientiae - MSc (Physics)Studying clustering on small scales (<10Mpc) over a large span of red- shifts allows us to connect galaxies to underlying cosmic large-scale structure, and thereby provide constraints on the physical processes that drive galaxy evolution. Relatedly, studying the relative bias of galaxies and their halo occupancy quanti es how the underlying dark matter distribution is traced by baryons in galaxies. Comparing model predictions to current and future multi-wavelength galaxy surveys, en- ables a greater understanding of how galaxy formation processes impact the relationship between galaxies and dark matter
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Saghiha, Hananeh [Verfasser]. "Comparing galaxy-galaxy(-galaxy) lensing in semi-analytic models and observations to study galaxy evolution / Hananeh Saghiha." Bonn : Universitäts- und Landesbibliothek Bonn, 2017. http://d-nb.info/113070467X/34.
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Machado, murtinheiras martins Andre. "Statistical analysis of large scale surveys for constraining the Galaxy evolution." Thesis, Besançon, 2014. http://www.theses.fr/2014BESA2026/document.
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La formation et l'évolution du disque épais de la Voie Lactée restent controversées. Nous avons utilisé un modèle de synthèse de la population de la Galaxie, le Modèle de la Galaxie de Besançon (Robin et al., 2003), qui peut être utilisé pour l'interprétation des données, étudier la structure galactique et tester différents scénarios de formation et évolution Galactique. Nous avons examiné ces questions en étudiant la forme et la distribution de métallicité du disque mince et du disque épais en utilisant l'approche de synthèse de la population. Nous avons imposé sur des simulations les erreurs d'observation et les biais afin de les rendre directement comparables aux observations. Nous avons corrigé les magnitudes et les couleurs des étoiles de la simulation, en utilisant un modèle d'extinction. Les modèles d'extinction disponibles ne reproduisent pas toujours la quantité exacte d'extinction le long de la ligne de visée. Un programme a été développé pour corriger la distribution de l'extinction en fonction de la distance le long de ces lignes. Les extinctions correctes ont ensuite été appliquées sur les simulations du modèle. Nous avons étudié la forme du disque mince en utilisant des données photométriques aux basses latitudes du sondage SDSS-SEGUE. Nous avons comparé qualitativement et quantitativement les observations et les simulations et nous avons essayé de contraindre la fonction de masse initiale. En utilisant la spectroscopie du relevé SEGUE, nous avons sélectionné les étoiles du turn-off de la séquence principale (MSTO) (Cheng et al 2012) et des géantes K pour étudier la distribution de métallicité du disque mince et du disque épais. Nous avons calculé une estimation de distance pour chaque étoile à partir de la relation entre les températures effectives et magnitudes absolues pour les catalogues observés et simulés. Ces deux catalogues ont les mêmes biais sur les distances, elles sont donc comparables. Nous avons développé un outil basé sur une méthode MCMC-ABC pour déterminer la distribution de la métallicité et étudier les corrélations entre les paramètres ajustés. Nous avons confirmé la présence d'un gradient de métallicité radiale de -0.079 ± 0.015 dex kpc−1 pour le disque mince. Nous avons obtenu une métallicité du disque épais au voisinage solaire de -0.47 ± 0.03 dex, compatible avec les résultats obtenus par les études précédentes. De plus, le disque épais ne montre pas de gradient, mais les données sont compatibles avec un gradient positif intérieur suivi d'un négatif extérieur. Nous avons ensuite appliqué les outils développés au relevé spectroscopique Gaia-ESO et calculé la distribution de métallicité des étoiles F/G/K dans le disque mince et épais en supposant une formation en deux époques du disque épais de la Voie Lactée. Nous avons obtenu une métallicité locale dans le disque épais de -0.23 ± 0.04 dex légèrement plus élevée que celle obtenue avec SEGUE mais en accord avec Adibekyan et al. (2013) et un gradient de métallicité radiale du disque épais en accord avec notre analyse précédente des données de SEGUE et la littérature. La métallicité locale est en accord avec la littérature au niveau de 3σ mais parce que les données GES sont préliminaires, une analyse plus approfondie avec plus de données et de meilleurs calibrations doit être faite. L'existence d'un gradient plat dans le disque épais peut être une conséquence d'une formation à partir d’un gaz turbulent et bien homogène, ou bien un fort mélange radial a brassé après coup les étoilesThe formation and evolution of the thick disc of the Milky Way remain controversial. We made use of a population synthesis model of the Galaxy, the Besançon Galaxy Model (Robin et al. 2003), which can be used for data interpretation, study the Galactic structure and test different scenarios of Galaxy formation and evolution. We examined these questions by studying the shape and the metallicity distribution of the thin and thick disc using the population synthesis approach. We imposed on simulations observational errors and biases to make them directly comparable to observations. We corrected magnitudes and colors of stars, from the simulation, using an extinction model. The available extinction models do not always reproduce the exact quantity of extinction along the line of sight. A code to correct the distribution of extinction in distance along these lines have been developed and the corrected extinctions have been applied on model simulations. We studied the shape of the thin disc using photometric data at low latitudes from the SDSS-SEGUE survey. We compared qualitatively and quantitatively observations and simulations and try to constrain the Initial Mass Function. Using the spectroscopic survey SEGUE we selected Main Sequence Turnoff (MSTO) stars (Cheng et al 2012) and K giants to study the metallicity distribution of the thin and thick discs. We computed a distance for each star from the relation between effective temperatures and absolute magnitudes for the observed and simulated catalogs. These two catalogues have the same biases in distances, therefore are comparable. We developed a tool based on a MCMC-ABC method to determine the metallicity distribution and study the correlations between the fitted parameters. We confirmed a radial metallicity gradient of -0.079 ± 0.015 dex kpc−1 for the thin disc. We obtained a solar neighborhood metallicity of the thick disc of -0.47 ± 0.03 dex similar to previous studies and the thick disc shows no gradient but the data are compatible with an inner positive gradient followed by a outer negative one. Furthermore, we have applied the developed tools to the Gaia-ESO spectroscopic survey and computed the metallicity distribution of F/G/K stars in the thin and thick disc assuming a two epoch formation for the thick disc of the Milky Way. We obtained a local metallicity in the thick disc of -0.23 ± 0.04 dex slightly higher than the one obtained with SEGUE but in agreement with Adibekyan et al. (2013) and a radial metallicity gradient for the thick disc in agreement with our previous analysis of SEGUE data and the literature. The local metallicity is in fair agreement with literature at the 3σ level but because the GES data is an internal release under testing further analysis with more data and better calibrations have to be done. The existence of a flat gradient in the thick disc can be a consequence of an early formation from a highly turbulent homogeneous well mixed gas, unless it has suffered heavy radial mixing later on
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Majewski, Steven R., Ricardo P. Schiavon, Peter M. Frinchaboy, Carlos Allende Prieto, Robert Barkhouser, Dmitry Bizyaev, Basil Blank, et al. "The Apache Point Observatory Galactic Evolution Experiment (APOGEE)." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/625493.
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The Apache Point Observatory Galactic Evolution Experiment (APOGEE), one of the programs in the Sloan Digital Sky Survey III (SDSS-III), has now completed its systematic, homogeneous spectroscopic survey sampling all major populations of the Milky Way. After a three-year observing campaign on the Sloan 2.5 m Telescope, APOGEE has collected a half million high-resolution (R similar to 22,500), high signal-to-noise ratio (>100), infrared (1.51-1.70 mu m) spectra for 146,000 stars, with time series information via repeat visits to most of these stars. This paper describes the motivations for the survey and its overall design-hardware, field placement, target selection, operations-and gives an overview of these aspects as well as the data reduction, analysis, and products. An index is also given to the complement of technical papers that describe various critical survey components in detail. Finally, we discuss the achieved survey performance and illustrate the variety of potential uses of the data products by way of a number of science demonstrations, which span from time series analysis of stellar spectral variations and radial velocity variations from stellar companions, to spatial maps of kinematics, metallicity, and abundance patterns across the Galaxy and as a function of age, to new views of the interstellar medium, the chemistry of star clusters, and the discovery of rare stellar species. As part of SDSS-III Data Release 12 and later releases, all of the APOGEE data products are publicly available.
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Glazebrook, Karl. "An infrared study of galaxy evolution." Thesis, University of Edinburgh, 1992. http://hdl.handle.net/1842/28109.
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This thesis describes a large-area 2μm survey undertaken on the U.K. Infrared Telescope in Hawaii, using a new infrared imaging camera. The survey convers 594 hskip 0.4cm and is complete and uniform to a limit of K = 17. The main aim of the survey was to construct a sample of galaxies, selected by their 2μm flux, for studies of galaxy evolution. The subsidiary aim was to survey the 2μm Universe and search for any new populations of infrared objects, such as protogalaxies and brown dwarf stars. The first half of this thesis is concerned with the analysis of astronomical data. The detailed methods for constructing the infrared survey are described, including flatfielding, astrometry, mosaicing and photometry. Also described are optical CCD observations which cover the survey area to provide optical-infrared colours of almost all the objects in the sample. The methods of reducing, calibrating and matching the CCD data with the infrared data are detailed. For the study of galaxy evolution the redshifts of 53 K band selected galaxies, with a well defined completeness, were measured using multiple object spectrographs. The reduction of the spectra and the methods used for securing the redshifts, including the cross-correlation technique, are described. The second half of this thesis is about the scientific results from this survey. Firstly, it appears that no new large populations of objects appear, in particular there appear to be no objects only detected in K. A few extremely red objects are found, however their true nature is unclear in the absence of spectra. The best evidence is that a few of them are very cool stars. Secondly, the galaxy population appears to have very red R-K colours, although not necessarily so red in B-K, and the K band number-magnitude counts exhibit a much smaller excess over the no-evolution prediction than do the B band optical counts. The K band counts are consistent with only a small amount of luminosity evolution.
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Smith, Rory. "Environmental effects on dwarf galaxy evolution." Thesis, Cardiff University, 2009. http://orca.cf.ac.uk/54852/.
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Using an N-body/Tree-code and Smoothed Particle Hydrodynamics, the influence of ram pressure stripping and harassment on an infalling star-forming galaxy population is investigated. In combination these mechanisms act to strip late-type dwarfs of their gas content in less than 0.5 Gyrs, causing a cessation of star-formation. As a result, late-type dwarfs evolve to colours typical of cluster dwarf ellipticals in less than 2 Gyrs, although the period in which they would be classified as transition objects lasts less than 1 Gyr. The rapid removal of a significant fraction of the dwarfs disk mass by ram pressure stripping causes morphological transformation of the stellar component, producing rotation-to-dispersion ratios in agreement with observations of cluster dwarf ellipticals. A Monte-Carlo simulation is utilised to quantify the effects of harassment, and strong, disruptive tidal encounters are found to be rare. The typical observable con sequences of harassment are found to be minor, producing very low surface brightness features (visible at surface brightnesses limits of > 30/j,b arcsec 2), and a reduction in dynamical mass-to-light ratios by roughly a factor of 2. The influence of harassment is found to be highly sensitive to the disk scale-length in exponential disks, and much less so to the mass of the galaxy. In general, ram pressure stripping is found to dominate the environmental influences on infalling late-type dwarfs, while the inclusion of the harassment model produces second-order effects only. Ram pressure stripping appears capable of forming the observed cluster dwarf population, both in colour and in morphology.
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Kotulla, Ralf Christian. "Galaxy evolution and the redshift desert." Thesis, University of Hertfordshire, 2011. http://hdl.handle.net/2299/5738.
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This thesis explores the evolution of galaxies from the onset of star formation shortly after the Big Bang until the present day. Particular emphasis lies on the redshift range z = 1.4 2.5, the so-called “redshift desert”, as it coincides with the peak epoch of cosmic star formation activity and mass assembly. Most of the information about galaxies and their evolution arrives in the form of their integrated light, i.e. the conglomeration of light emitted by stars of various ages and metallicities. In order to interpret the observed spectra and magnitudes, and to extract the physical parameters we therefore require models. This holds true in particular for galaxies too faint to target them spectroscopically, and for which redshifts and physical parameters derived from only their photometry is the only feasible way to study them in more detail. This thesis is concerned with such models, and describes how GALEV evolutionary synthesis models describe the spectral and chemical evolution of galaxies, accounting for gaseous emission and the increasing initial abundances of successive stellar generations, how they compare to observations and what we can learn from their application. Based on a large model grid, covering all observed galaxy evolution stages, I find that sub-solar metallicities have significant impact on the spectra of galaxies, and can lead to systematic errors and biases if not accounted for. A comparison of models with different metallicities furthermore reveals that photometric redshifts are also systematically biased if sub-solar metallicities are not properly accounted for. I also note that even a small mass-fractions of young stars can dominate the overall spectrum, leading to a large underestimation of the mass and age of the stellar population. The models explain not only the colour evolution of galaxies observed at a range of redshifts, but also their physical parameters. I show that with magnitudes in only a few bands we can successfully explain not only the masses of galaxies, but also their star formation rates and, where available from observations, their metallicities. If additional data are available, the grid of models can be used to refine colour selection criteria and to break degeneracies, e.g. between dust-reddened actively star-forming galaxies and intrinsically old, passively evolving galaxies. Using GAZELLE, a photometric redshift code that is purpose-tailored to harmonise with these models, I can extract accurate redshifts and a wealth of physical parameters from the largest ever sample of observed multi-wavelength photometry of galaxies. I then compare our findings with semi-analytical models that trace the evolution of individual galaxies based on cosmological simulations. In my sample I find a significant population of high-mass galaxies that is not accounted for by this class of models. Furthermore a small percentage of massive, yet starforming galaxies challenges our idea on how these galaxies form and evolve. In an appendix to this thesis I present a complementary approach to reconstruct the evolution of galaxies, using star clusters as tracers. I introduce a new technique to break the age-metallicity degeneracy and obtain individual ages and metallicities for a sample of globular clusters, revealing a merger of two Sb/Sc-type spirals 2 Gyrs ago in NGC 4570, a lenticular galaxy in the Virgo cluster. Also in the appendix I show that, at least in the studied galaxy Arp 78, the initial mass function conforms with our assumptions and does not change in low-density environments as recently predicted. Although studies of galaxy evolution are a major field in astronomy, there is still a lot more to be done to reveal the inner workings of these island universes, and this thesis also addresses how to continue and improve the work presented herein.
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Hennig, Christina. "The galaxy population evolution of Sunyaev." Diss., Ludwig-Maximilians-Universität München, 2015. http://nbn-resolving.de/urn:nbn:de:bvb:19-184237.
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This thesis presents a study of the galaxy populations in massive galaxy clusters that have been selected via the Sunyaev - Zeldovich Effect from the South Pole Telescope. The clusters have multiband optical imaging data from the Dark Energy Survey (DES). Each cluster has a robust mass estimate and with the deep DES data they cover a redshift range between 0 and 1.1. This makes it an ideal cluster sample to study evolutionary trends of the galaxy populations with mass and redshift.
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Wilman, David John. "Galaxy evolution in groups and clusters." Thesis, Durham University, 2004. http://etheses.dur.ac.uk/2816/.
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In this thesis, we investigate the extent to which galaxy evolution is driven by processes common to the group and cluster environments. A bimodality of galaxy properties such as star formation, strongly dependent upon the local overdensity of galaxies, suggests that the passive, early type galaxies common to groups and clusters originate in transformation processes, which are nurtured by the environment. This can only be important to global galaxy evolution if transformations are common in groups, which contain z 50% of the local galaxy population. We present deep Magellan spectroscopy and HST ACS imaging of our group and field samples at 0.3 ˂ z ˂ 0.55, selected from the CN0C2 survey by Carlberg et al. (2001b). We find that these groups contain significantly more passive galaxies than the field, with excesses of S0, elliptical and passive spiral galaxy types. The morphological composition is closely matched to that of irregular and X-ray-faint clusters at a similar epoch. In contrast with a low-redshift group sample selected from 2dFGRS (Eke et al, 2004), we find that the fraction of passive galaxies, fp， is strongly evolving in the group environment, with parallel evolution in the field population. Simple models confirm that galaxy transformations are required to match the evolution of both group and field populations. Qualitatively similar evolution and dependence on environment is found in physically-motivated simulations. However, these do not quantitatively match the environmental nor luminosity dependence in the evolution of fp. We also present a complementary method using photometric redshifts to identify infalling groups in the outskirts of clusters with Wide Field Imaging (WFI) technology. Finally, we identify the key developments which will help to unravel the history of galaxy evolution in coming years.
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Garn, Timothy Seymour. "610-MHz observations of galaxy evolution." Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611171.
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Burton, Christopher Steven. "The environmental dependence of galaxy evolution." Thesis, University of Hertfordshire, 2013. http://hdl.handle.net/2299/12572.
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Observations of galaxy environments have revealed numerous correlations associated with their intrinsic properties. It is therefore clear that if we are to understand the processes by which galaxies form and evolve, we have to consider the role of their immediate environment and how these trends change across cosmic time. In this thesis, I investigate the relationship between the environmental densities of galaxies and their associated properties by developing and implementing a novel approach to measuring galaxy environments on individual galaxy scales with Voronoi tessellations. Using optical spectroscopy and photometry from GAMA and SDSS, with 250μm far-infrared observations from the Herschel-ATLAS SDP and Phase-One fields, the environmental and star formation properties of far-infrared detected and non–far-infrared detected galaxies are compared out to z ∼ 0.5. Applying statistical analyses to colour, magnitude and redshift-matched samples, I show there to be significant differences between the normalised density distributions of the optical and far-infrared selected samples, at the 3.5σ level for the SDP increasing to > 5σ when combined with the Phase-One data. This is such that infrared emission (a tracer of star formation activity) favours underdense regions, in agreement with previous studies that have proposed such a correlation. I then apply my method to synthetic light cones generated from semianalytic models (SAMs), finding that over the whole redshift distribution the same correlations between star-formation rate and environmental density are found. However, as the SAMs restrict the role of ram-pressure stripping, the fact that we find the same qualitative results may preclude ram-pressure as a key mechanism in truncating star formation. I also find significant correlations between isothermal dust temperature and environment, such that the coldest sources reside in the densest regions at the 3.9σ level, indicating that the observed far-infrared emission in these densest regions is the product of ISM heating by the older stellar populations. I then extend my analysis to a deeper sample of galaxies out to z ∼ 2.2, combining near-infrared and optical photometry from the VIDEO and CFHTLS-D1 observations, cross-matched in colour, magnitude and redshift against 1.4 GHz VLA radio observations. Across the entire radio sample, galaxies with radio detected emission are found to reside in more overdense environments at a 4.0σ significance level. I then divide my radio sample to investigate environmental dependence on both radio detected star-forming galaxies and radio detected AGN individually, based upon a luminosity selection defined as L = 1023 W Hz−1. The same trends with environment are shown by my Radio-AGN sample (L > 1023 W Hz−1) which favour overdense regions at the 4.5σ level, suggestive of the interaction processes (i.e. major mergers) that are believed to trigger accretion, in agreement with earlier work that has suggested such a relationship. At lower radio luminosities, my Radio-SF sample (L < 1023 W Hz−1) also display a significant trend towards overdense regions in comparison to my nonradio detected sample, at the less significant level of 2.7σ. This is suggestive of the low overall bolometric luminosity of radio emission in star forming galaxies, leading to only the brightest radio emitting star forming galaxies being observed and a bias towards overdense regions. This is in addition to the fact that the luminosity selection used to separate AGN from star forming galaxies is not a perfect selection and open to AGN contamination in the low-luminosity sample. I conclude that the next generation of deep radio surveys, which are expected to reach many orders of magnitude deeper than current observations, will remove radio-loud AGN contamination and allow for the detection of low-luminosity star forming galaxies via radio emission out to high redshifts. This work has allowed for the environments of galaxies to be probed on smallerscales and across both wider and deeper samples than previous studies. With significant environmental correlations being returned, this indicates that the established processes responsible for such trends must have influence on the most local of scales.
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Hirashita, Hiroyuki. "Galaxy Evolution through Far-Infrared Radiation." 京都大学 (Kyoto University), 2001. http://hdl.handle.net/2433/150831.
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本文データは平成22年度国立国会図書館の学位論文(博士)のデジタル化実施により作成された画像ファイルを基にpdf変換したものであるKyoto University (京都大学)
0048
新制・課程博士
博士(理学)
甲第8727号
理博第2299号
新制||理||1203(附属図書館)
UT51-2001-F57
京都大学大学院理学研究科物理学・宇宙物理学専攻
(主査)助教授 嶺重 慎, 助教授 太田 耕司, 教授 舞原 俊憲
学位規則第4条第1項該当
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Wijesinghe, Dinuka. "Galaxy star formation rates and their relation to galaxy environments." Thesis, The University of Sydney, 2012. https://hdl.handle.net/2123/28926.
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This thesis investigates various methods of dust obscuration measurements in order to derive accurate SFRs which I then use to investigate the SFR-density relation.
I present self-consistent star formation rates derived through pan-spectral analysis of galaxies drawn from the Galaxy and Mass Assembly (GAMA) survey. I determine the most appropriate form of dust obscuration correction via application of a range of extinction laws drawn from the literature as applied to Ha, [On] and UV luminosities. I consider several different obscuration curves, including those of Milky Way, Calzetti (2001) and Fischera and Dopita (2005) and their effects on the observed luminosities. I find that the Fischera & Dopita (2005) obscuration curve with an Rv value of 4.5 gives the best agreement between the different SFR indicators. The 2200 A feature needs to be removed from this curve to obtain complete consistency between all SFR indicators suggesting that this feature may not be common in the average integrated attenuation of galaxy emission.
The findings of this work indicate that incorporating a more direct measure of dust such as the far infrared (FIR) and near infrared (NIR) may help develop more accurate obscuration corrections particularly for the ultraviolet (UV) wavelength region as the UV radiation absorbed by dust is re-emitted in the infrared (IR). To carry out this analysis I combine the multiwavelength data from GAMA with data from the Herschel ATLAS (HATLAS) survey. I explore the connections between each of the following: the ultraviolet (UV) spectral slope, /3, the Balmer decrement, and the far infrared (IR) to 150 nm far ultraviolet (FUV) luminosity ratio. I reiterate the finding of other authors that there is a large scatter between the Balmer decrement and the /3 parameter, and that /3 may be poorly constrained when derived from only two broad passbands in the UV. While there is a stronger correlation between the IR to FUV luminosity ratio and the /3 parameter than with the Balmer decrement, neither of these correlations are particularly tight, and dust corrections based on /3 for high redshift galaxy SFRs must be treated with caution.
I then used the SFRs that were derived using the above obscuration correction formalism to investigate the known SFR-density relationship and explore in detail the dependence of SFR on stellar mass and density. I show that the SFR-density trend is only visible when I include the passive galaxy population along with the star-forming population. This SFR-density relation is absent when I consider only the star-forming population of galaxies, consistent with previous work. I find that stellar mass has the strongest influence on SFR and EWHa with the environment having no significant effect on the star-formation properties of the star forming population. The observation that the trends with density are due to the changing morphology fraction with density implies that the timescales must be very short for any quenching of the SFR in infalling galaxies. Alternatively galaxies may in fact undergo predominantly in-situ evolution where the infall and quenching of galaxies from the field into dense environments is not the dominant evolutionary mode.
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FUMAGALLI, MICHELE. "Food for stars: The role of hydrogen in the formation and evolution of galaxies." Doctoral thesis, University of California Santa Cruz, 2012. http://hdl.handle.net/10281/280709.
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The current cosmological model, the Lambda CDM theory, describes with remarkable precision the assembly and growth of the large scale structures and of the dark matter halos in our Universe. A comprehensive theory for the baryon processes that take place within dark matter halos is, instead, still the subject of active research. The three major ingredients of this theory are known: accretion of hydrogen from the intergalactic medium, star formation, and feedback mechanisms in the form of galactic winds. However, the recipe to blend them together has not yet been found. This thesis focuses on the role that two of these ingredients have in the assembly and evolution of galaxies. The underlying questions that this work aims to address are how the accretion of hydrogen onto galaxies occurs and what the conditions needed to convert this raw fuel into stars are. The instruments used for this investigation are diverse, because of the multiplicity of physical processes, spatial scales, and cosmic epochs involved in the problem. Theory, or more specifically the analysis of hydrodynamic simulations to unveil gas accretion onto high-redshift galaxies, is the starting point for this work. In the second part, spectroscopy of bright quasars is used to probe the physical properties of gas and metals around and within distant galaxies. These observations are systematically compared to model predictions. Deep optical imaging is also used to connect the star formation rates of these galaxies to the gas properties that are measured in absorption. Finally, in the third part, the relationship between hydrogen and star formation on smaller scales is investigated by means of multiwavelength observations of local galaxies. This thesis contributes to the aforementioned open questions in four ways. First, it is shown that the accretion of gas onto galaxies as predicted by current simulations imprints characteristic signatures on the distribution of hydrogen and metals of a particular family of absorption line systems, the Lyman limit systems. Second, new spectroscopic observations that led to the discovery of gas clouds with physical properties that match predictions from simulations are presented, paving the way for establishing empirically how galaxies acquire their gas. Third, through a comparison of the hydrogen content and the star formation rates of distant galaxies, this thesis confirms how the presence of significant amounts of hydrogen is not a sufficient condition for the onset of star formation. Finally, after assessing the validity of star formation models in environments that are common to high redshift galaxies, these findings have been interpreted as inefficient star formation in regions with low gas column density and low metallicity.
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Gabasch, Armin. "Galaxy Evolution in the Fors Deep Field." Diss., lmu, 2004. http://nbn-resolving.de/urn:nbn:de:bvb:19-31122.
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Collobert, Maela. "Galaxy evolution in field and cluster environments." Thesis, University of Oxford, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437368.
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Lane, Kyle P. "Galaxy evolution through clusters and cosmic time." Thesis, University of Nottingham, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.490988.
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Horleston, Nathan James. "Observing the Evolution of the Galaxy Distribution." Thesis, University of Bristol, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.503899.
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Brough, Sarah. "Environmental dependence of brightest cluster galaxy evolution." Thesis, Liverpool John Moores University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.431286.
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Hine, Nancy. "Galaxy evolution in a z~3 protocluster." Thesis, University of Hertfordshire, 2017. http://hdl.handle.net/2299/19098.
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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.
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Just, Dennis William. "The Influence of Environment on Galaxy Evolution." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/265357.
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We study the influence of environment on galaxy evolution by focusing on two galaxy types known for their connection to dense environments, S0s and Brightest Cluster Galaxies (BCGs). Our goal is to identify the mechanisms responsible for the properties of galaxies in groups and clusters. We first examine the effects of environment on S0 formation over the past ~7 Gyr by tracing the increasing S0 fraction in clusters at two mass scales. We find the build-up of S0s driven by groups/clusters with velocity dispersions σ ≲ 750 km s⁻¹, suggesting mechanisms that operate most efficiently via slow encounters (e.g., mergers and tidal interactions) form S0s.With less-massive halos identified as the site for S0 formation, we test whether another route to S0 formation exists, not in isolated groups but rather in a system of four merging groups (SG1120). We place limits on how recent the S0s in that system could have formed, and finding no star formation, conclude they formed ≳ 1 Gyr prior to SG1120's current configuration, when they were in more isolated groups. We next explore cluster outskirts to constrain the number of infalling galaxies that need to be transformed and whether that process has already begun. We find the red fraction of infalling galaxies is elevated relative to the field, and that red galaxies are more clustered than blue ones, a signature of "pre-processing". We disentangle the relative strength of global versus local environment on galaxy transformation by comparing the correlation of red fraction with radius and local density. We find that both parameters are connected with the red fraction of galaxies. Finally, we measure the frequency of galaxies falling into the cluster that are bright enough to supplant the current BCG and compare the results to models. We find in ~ 85% of our clusters that the BCG is secure and remains in its priviledged state until z ~ 0.From these analyses, we find that intermediate density environments (groups and cluster outskirts) are the key site to forming S0 galaxies, and that BCGs, while not exclusively a cluster phenomenon, are well established by the redshifts we explore.
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Fan, Xi Long. "Galaxy evolution by chemical and SED model." Doctoral thesis, Università degli studi di Trieste, 2012. http://hdl.handle.net/10077/7429.
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2010/2011In this thesis, we have studied the ISM, QSO, LGRB hosts and LBGs by galactic chemical evolution and spectro-photometric models. We also tested the so-called mono- lithic scenario of elliptical galaxies formation. Here we present the main results of this work: 1. The star formation history is the main driver of galaxy evolution. The predictions of elliptical chemical evolution models with the so-called monolithic scenario of elliptical galaxies formation are consistent with the data of high redshift LBGs and QSOs. Both the infall and the star formation timescale are suggested to decrease with galactic mass. This scenario is confirmed by the spectro-photometric models by reproducing the average SED of MIPS-LBGs. This so-called “ downsizing” of SFH is consistent with many observations. 2. Our M = 1012M⊙ elliptical model can reproduce super-massive BH mass, stellar mass, gas mass and dust mass of one of the most distant QSO ever observed J1148+5251 (z ≃ 6.4). The same model can also reproduce [N/C] versus [C/H] and [Si/C] versus [C/H] of the NLRs in QSO hosts. The very high C abundance observed in these QSOs can be explained only by assuming yields with mass loss from massive stars with a strong dependence on metallicity, as those of Maeder (1992) 3. Our elliptical models suggested the LBGs at hight redshift are likely to be young (age < 0.6 Gyr) ellipticals. This picture is consist with the results of spectro- photometric models. By chemical evolution models, we found that, LBGs in A- MAZE and LSD samples, CB 58, Clone and Cosmic Horseshoe are of intermediate mass(1010 − 3 · 1010M⊙). Our elliptical model for 3 · 1010M⊙ well reproduces the [O/H] abundance as a function of redshift for these LBGs. By spectro-photometric models, we found that theMIPS-LBGs are more massive (∼ 1011M⊙). Our spectro- photometric models for 1011M⊙ well reproduce the average SED of MIPS-LBGs. 4. Our elliptical models suggested that if the observed high-redshift LGRB-DLAs and local LGRB host galaxies belonged to an evolutionary sequence, they should be irregulars with a common galaxy-formation redshift as high as zf = 10, observed at different phases of their evolution. We cannot exclude, however, that they correspond to the outermost regions of spiral disks, since their properties are similar to those of irregulars. Elliptical galaxies cannot be LGRB host galaxies at low 111 redshift and that they are very unlikely hosts of LGRB-DLAs even at high redshift, because of their rapid chemical enrichment at high redshift following the occurrence of a galactic wind several Gyrs ago and subsequent passive evolution. 5. Our elliptical models suggested that a dust mass-stellar mass relation exists, with more massive galaxies attaining a higher dust content at earlier time. The dust evolution in ISM make the main contribution for the large amount of dust in high redshift QSOs. QSO itself produced dust but this production appears negligible compared to that from stellar sources, unless one focuses on the very central regions at times very close to the galactic wind onset. 6. The dust mass estimation in the average MIPS-LBGs based on the combination of our elliptical models and spectro-photometric models is not consistent with the one based on simple temperature grey-body fitting. The Milky Way dust parameters can not reproduce the average SED of MIPS-LBGs with the SFHs from chemical evolution models. The more dense dusty environments and flatter dust size distributions are needed to reproduce the average SED of MIPS-LBGs with these SFHs. 7. IGIMF of starburst galaxies can improve the [α/Fe] ratios, however it still can- not solve the discrepancy between predictions and data. Dust effect is the most plausible solution.
XXIV Ciclo
1981
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Pracy, Michael Benjamin Physics Faculty of Science UNSW. "The properties and evolution of galaxy populations in the rich cluster environment." Awarded by:University of New South Wales. Physics, 2006. http://handle.unsw.edu.au/1959.4/23033.
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This thesis is concerned with the role the rich cluster environment plays in the evolution of its galaxy population. We approach this issue from two angles, first we use deep wide-field imaging to investigate the effect of the cluster environment on the spatial and luminosity distribution of galaxies. Secondly, we focus on one particularly interesting class of galaxy, the enigmatic E+A galaxies, using a combination of state-of-the-art telescopes and novel instrumentation to elucidate the physical mechanisms and environmental influences causing the rapid change in star-formation activity in these galaxies. We present results from a deep photometric study of the rich galaxy cluster Abell 2218 (z=0.18) based on Hubble Space Telescope images. These have been used to derive the cluster luminosity function to extremely faint limits. We find the faint-end slope of the luminosity function to vary with environment within the cluster - in the sense that the ratio of `dwarf' galaxies to `giant' galaxies increases in the lower-density outskirt regions. Using imaging obtained with the Isaac Newton Telescope (INT) we confirm the presence of luminosity segregation in Abell 2218. However, luminosity segregation in clusters does not appear to be ubiquitous, with two other clusters studied with the INT (A119 at z=0.04 and A2443 at z=0.11) showing no sign of luminosity segregation of their galaxy populations. We use integral field spectroscopy of a sample of E+A galaxies in intermediate redshift clusters, obtained with the FLAMES system on the European Southern Observatory's VLT and the GMOS instrument on Gemini-North, to determine the radial variation in the strength of Hdelta absorption in these galaxies, and hence map out the distribution of the recently formed stellar population. We find a diversity of behaviour amongst these galaxies in terms of the radial variation in Hdelta absorption: with gradients that are either negative, flat, or positive. By comparing with numerical simulations we suggest that the first of these different types of radial behaviour provides evidence for a merger/interaction origin, whereas the latter two types of behaviour are more consistent with the truncation of star formation in normal disk galaxies.
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Impey, C. D., and G. D. Bothun. "MALIN: A Quiescent Disk Galaxy|MALIN 1: A Quiescent Disk Galaxy." Steward Observatory, The University of Arizona (Tucson, Arizona), 1988. http://hdl.handle.net/10150/623912.
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We present new optical and radio spectroscopic observations of the remarkable galaxy
Malin 1. This galaxy has unique features that include an extremely low surface brightness
disk with an enormous mass of neutral hydrogen, and a low luminosity Seyfert nucleus.
Malin 1 is exceptional in its values of MHO, LB, and MHI /Ln, and modest in its surface
mass density of gas and stars. Spirals with large Min /LB tend to have low mean column
densities of HI, and are close to the threshold for star formation due to instabilities in
a rotating gas disk. In these terms, Malin 1 has a disk with extremely inefficient star
formation. The bulge spectrum is dominated by the absorption features of an old, metal
rich stellar population, although there is some evidence for hot (young) stars. The emission
line excitations and widths in the nucleus are typical of a Seyfert galaxy; but Malin 1 is in
the lowest 5% of the luminosity function of Seyferts, despite a copious fuel supply. Malin 1
is in a low density region of the universe. We propose it as an unevolving disk galaxy, where
the surface mass density is so low that the chemical composition and mass fraction in gas
change very slowly over a Hubble time. Its properties are similar to those of the damped
Lyman -a absorption systems seen in the spectra of high redshift quasars. We emphasize
that there are strong observational selection effects against finding gas -rich galaxies that
are both massive and diffuse. Finally, we suggest that large and massive HI disks may
have formed as early as z - 2, and remained quiescent to the present day.
Subject headings : individual (Malin 1) - galaxies : photometry - galaxies : Seyfert -
galaxies : stellar content - radio sources : 21 cm radiation - stars : formation
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Duong, Ly. "Unravelling the evolution of the Galactic stellar disk and bulge." Phd thesis, Canberra, ACT : The Australian National University, 2018. http://hdl.handle.net/1885/149502.
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The formation and evolution of spiral galaxies is a research
topic central to modern Astronomy. In this context, the Milky Way
offers a unique opportunity for astronomers to study a spiral
galaxy in detail and thus informs many aspects of galaxy
formation theory.
The observational signatures of Galactic stellar components
provide clues to its assembly history. This thesis is focused on
two main components of the Galaxy: the stellar disk and bulge. In
particular, we examine the chemical properties of these
components and their implications for Galactic evolution. The
data in this thesis were obtained with HERMES, a new
high-resolution optical spectrograph on the Anglo Australian
Telescope. The disk sample consists of over 3000 giant-branch
stars, extending up to 4 kpc in height from the Galactic plane.
The thin disk (low-α population) exhibits a steep negative
vertical metallicity gradient, a signature observed in galaxy
evolution models where radial migration plays an important role.
The thick disk (high-α population) has a weaker vertical
metallicity gradient, which could have arisen from a settling
phase of the primordial disk. The [α/Fe] ratios of the thin and
thick disk populations are distinct and nearly constant with
height. This indicates the two populations were formed in very
different conditions, and although the high-α population likely
experienced a settling phase, its formation timescale was fast
still, in the order of a few Gyrs.
To investigate the chemistry of the Galactic bulge and its
connection to the disk, we obtained abundance ratios of 18
elements for more than 800 red giants. The [α/Fe] abundance
ratios show vertical variations that are consistent with the
distribution of bulge metallicity components: at high latitudes
[α/Fe] is enhanced as the metal-poor component dominates; closer
to the plane, the metal-rich components contribute lower [α/Fe].
However, at fixed metallicity, all elements show uniform
abundance ratios with latitude. We observe normal [Na/Fe] ratios
that do not vary as a function of latitude at fixed metallicity,
indicating that the bulge does not contain strongly
helium-enhanced populations as observed in globular clusters.
By comparing our results with that of the GALAH survey, we
conclude that there are similarities between the bulge and disk
in terms of their chemistry. However, the more metal-poor bulge
population ([Fe/H] ≲ -0.8) shows enhanced abundance ratios
compared to the disk for some light, alpha, and iron-peak
elements that are associated with
core-collapse supernovae (SNeII). This population may have
experienced a different evolution to bulge stars of disk origin.
Moreover, the [La/Eu] abundance ratios suggest higher r-process
contribution in the bulge, which indicates that overall the bulge
experienced a higher star formation rate than the disk.
Keywords: Galaxy, stellar populations, stellar abundances, disk,
bulge, galaxy formation, galaxy evolution
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Laine, J. (Jarkko). "Understanding the formation and evolution of disc break features in galaxies." Doctoral thesis, University of Oulu, 2016. http://urn.fi/urn:isbn:9789526213040.
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Abstract
The discs in galaxies are radially extended, rotationally supported, flattened systems. In the cosmological Lambda Cold Dark Matter model the formation of the discs is intimately connected with galaxy formation. Generally it is assumed that the discs have exponentially decreasing stellar surface brightness profiles, but completely satisfactory theoretical explanation for this has not been presented. Large number of studies in the past decade have challenged this view, and have found a change in the slope of the surface brightness profile in the outer regions of many galaxies discs: the surface brightness can decrease more, or less, steeply than in the inner regions. The transition between the two slopes is often called a disc break. Consequently, the discs are divided in three major categories: single exponential Type I, down-bending break Type II, and up-bending break Type III. Formation of these break features has been linked to the initial formation of the discs, internal evolution, and also with the interactions between galaxies. By studying the detailed properties of the disc break features, the evolutionary history of discs, and galaxies in general, can be better understood.
The thesis work focuses on the structural analysis of the galaxies in the Spitzer Survey of Stellar Structure in Galaxies (S4G), which consists of 2352 galaxies observed in the 3.6 and 4.5 µm mid-infrared wavelengths with the Spitzer space telescope. Work has been carried out as a part of the data-analysis pipelines of the S4G survey, utilizing surface photometry. In addition, special emphasis has been put on the study of the disc and disc break properties in a wide range of galaxy morphological types and stellar masses. The thesis work attempts to at least partially understand how galaxy stellar mass and observed wavelength affect the properties of the discs and breaks, and how galaxy structural components are connected with the breaks.
The data comprises mainly of the 3.6 µm infrared data, providing a view to the stellar mass distribution of galaxies. We find that the Type II breaks are the most common disc profile type, found in 45 ± 2% of the sample galaxies, consisting of 759 galaxies in the stellar mass range 8.5 ≲ log10(M*/M⊙) ≲ 11. Type I discs are found in 31 ± 2%, and the Type III breaks in 23 ± 2% of the sample. The fraction of the profile types also depends of the galaxy stellar mass: fractions of the Types II and III increase, while Type I fraction decreases, with increasing stellar mass. We attribute these changes with stellar mass to the increased frequency of bar resonance structures in higher mass galaxies, which are commonly associated with a Type II break, and to the increased fraction of Type III profiles in generally more massive early-type disc galaxies. In addition to the Type II breaks associated with bar resonance structures, we find that nearly half of these breaks relate to the visual spiral outer edge, confirming previous results of the Type II break connection with galaxy structure, and thus the internal evolution rather than initial formation of discs.
Complementary data in optical wavelengths from the Sloan Digital Sky Survey shows a strong change in the properties of the discs inside the Type II breaks, indicating that the inner discs are evolving via star formation. In late-type spiral galaxies (T ≳ 4) with a Type II break, possible evidence of radial stellar migration is found in the outer disc: the slope of the surface brightness profile is shallower in the infrared compared to optical wavelengths, indicating that older stellar populations are more evenly spread throughout the disc. Formation of the Type I and III profiles remain poorly understood. However, indication that some of the Type III profiles are formed by environmentally driven processes is found, with a correlation between the properties of the local environment and the disc profile parameters. Furthermore, indication of star formation possibly causing the up-bends in spiral galaxies is found through a presence of young stellar population in the outer disc section.
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Czekaj, Maria A. "Galaxy evolution: A new version of the Besançon Galaxy Model constrained with Tycho data." Doctoral thesis, Universitat de Barcelona, 2012. http://hdl.handle.net/10803/123978.
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The understanding of the origin and evolution of the Milky Way is one of the primary goals of the Gaia mission (ESA, launch autumn 2013). In order to study and analyse fully the Gaia data it will be useful to have a Galaxy model able to test various hypothesis and scenarios of galaxy formation and evolution. Kinematic and star count data, together with the physical parameters of the stars - ages and metallicities-, will allow to characterize our galaxy's populations and, from that, the overall Galactic gravitational potential. One of the promising procedures to reach such goal is to optimize the present Population Synthesis models (Robin et al. (2003)) by fitting, through robust statistical techniques, the large and small scale structure and kinematics parameters that best will reproduce Gaia data. This PhD thesis was focused on the optimization of the structure parameters of the Milky Way Galactic disc. We improved the Besançon Galaxy Model and then by comparing the simulations to real data studied the process of Galaxy evolution.
The Besançon Galaxy Model is a stellar population synthesis model, built over the last two decades in Besançon (Robin and Crézé(1986); Robin et al. (2003)). Until now the star production process in that model was based on the drawing from the so called Hess diagrams. Each Galaxy population had one such a diagram, which was calculated once given a particular Initial Mass Function (IMF), Star Formation Rate (SFR), evolutionary tracks and age-metallicity relation and since then remained fixed in the model. As that feature was not enabling to test any other scenario of Galaxy evolution, because none of the evolutionary parameters could be modified, it was one of the biggest weaknesses of the model. It has served us as a motivation to dedicate this PhD project to the construction of a new version of the model, which would be able to handle variations of the SFR, IMF, evolutionary tracks, atmosphere models among others. When the evolutionary parameters are changed one must repeat the process of accomplishing the dynamical self-consistency of the model as described in Bienayme et al. (1987). For that
we have recalculated the Galactic gravitational potential for all new evolutionary scenarios, which have been tested. The second very important improvement of the model, which is delivered in this thesis, is the implementation of the stellar binarity. That is, the new version of Besançon Galaxy Model presented here is not any more a single star generator, but it considers binary systems maintaining constraints on the local mass density. This is an important change since binaries can account for about 50 % of the total stellar content of the Milky Way.
Once the tool was developed we tested several possible combinations of IMF and SFR in the Solar Neighborhood and identified those which best reproduce the Local Luminosity Function and Tycho-2 data. We have accomplished an unprecedented task using the new version of the model, namely we have performed the whole sky comparisons for a magnitude limited sample in order to study the bright stars. The Tycho-2 catalogue turned out to be an ideal sample for that task due to its two important advantages, the homogeneity and completeness until VT ~ 11 mag.
Different techniques and strategies were designed and applied when comparing the simulated and the real data. We have looked at small and specific Galactic directions and also performed general comparisons with a global sky coverage. In order to increase the efficiency of numerous simulations and comparisons, a processing pipeline based on C, Java and scripting programming languages has been developed and applied. It is a fully automated, portable and robust tool, allowing to split the work across several computational units.La misión Gaia (ESA, 2013) revolucionará el conocimiento sobre el origen y la evolución de nuestra Galaxia. Una óptima explotación científica de sus datos requiere disponer de modelos que permitan contrastar hipótesis y escenarios sobre estos procesos de formación. En esta tesis hemos optimizado el modelo de síntesis de poblaciones estelares de Besançon, ampliamente utilizado por la comunidad internacional, centrándonos en la componente del disco delgado. Hemos diseñado, desarrollado, implementado y testeado una nueva estructura de generación de las estrellas que permite encontrar la mejor combinación de función inicial de masa (IMF) y ritmo de formación estelar (SFR) que ajusta a las observaciones. El código permite imponer la autoconsistencia dinámica, recalculando el potencial galáctico para cada nuevo escenario de evolución. También, por primera vez, se generan sistemas binarios bajo esta consistencia dinámica, marcada por la función de luminosidad observada en el entorno solar. Esta, junto con el catálogo Tycho, han sido los dos ingredientes observacionales clave para el ajuste entre modelo y observación. También, por primera vez, hemos conseguido un ajuste aceptable a los recuentos estelares de todo el cielo hasta V=11. Se han evaluado con rigor los efectos en los recuentos estelares derivados del uso de los modelos de atmosfera, de evolución estelar y de extinción interestelar así como de parámetros tan críticos como la masa dinámica del sistema galáctico. El ajuste de estos ingredientes usando el catálogo Tycho nos ha permitido confirmar, de una vez por todas, que la SFR en el disco galáctico no ha sido constante sino decreciente desde los inicios de la formación de esta estructura. En conclusión, esta tesis proporciona un nuevo código, optimizado y flexible en el uso de los ingredientes básicos, en el que se ha realizado una rigurosa evaluación y actualización de los ingredientes que lo componen.
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Bahé, Yannick Michael. "Environmental influence on galaxy evolution in cosmological simulations." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648140.
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Guo, Qi. "Galaxy formation and evolution in a LamdaCDM universe." kostenfrei, 2009. http://edoc.ub.uni-muenchen.de/10678/.
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Linden, Anja von der. "Galaxy Evolution from the SDSS and EDisCS Surveys." Diss., lmu, 2007. http://nbn-resolving.de/urn:nbn:de:bvb:19-88794.
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Kitzbichler, Manfred G. "Galaxy formation and evolution in the Millennium Simulation." Diss., lmu, 2008. http://nbn-resolving.de/urn:nbn:de:bvb:19-95401.
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Guo, Qi. "Galaxy Formation and Evolution in a LCDM Universe." Diss., lmu, 2009. http://nbn-resolving.de/urn:nbn:de:bvb:19-106781.
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Pope, Erin Alexandra. "The role of submillimetre galaxies in galaxy evolution." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/31466.
Full textAbstract:
This thesis presents a comprehensive study of high redshift submillimetre galaxies (SMGs) using the deepest multi-wavelength observations. The submm sample consists of galaxies detected at 850 μm with the Submillimetre Common User Bolometer Array (SCUBA) in the Great Observatories Origins Deep Survey-North region. Using the deep Spitzer Space Telescope images and new data and reductions of the Very Large Array radio data, I find statistically secure counterparts for 60% of the submm sample, and identify tentative counterparts for most of the remaining objects. This is the largest sample of submm galaxies with statistically secure counterparts detected in the radio and with Spitzer. This thesis presents spectral energy distributions (SEDs), Spitzer colours, and infrared (IR) luminosities for the SMGs. A composite rest-frame SED shows that the submm sources peak at longer wavelengths than those of local ultraluminous IR galaxies (ULIRGs), i.e. they appear to be cooler than local ULIRGs of the same luminosity. This demonstrates the strong selection effects, both locally and at high redshift, which may lead to an incomplete census of the ULIRG population. The SEDs of submm galaxies are also different from those of their high redshift neighbours, the near-IR selected BzK galaxies, whose mid-IR to radio SEDs are more like those of local ULIRGs. I fit templates that span the mid-IR through radio to derive the integrated 1R luminosities of the submm galaxies and find a median value of L[sub IR](8-1000 μm) = 6.0 x 10¹²L [Special characters omitted] . I also find that submm flux densities by themselves systematically overpredict L[sub IR] when using templates which obey the local ULIRG temperature-luminosity relation. The SED fits show that SMGs are consistent with the correlation between radio and IR luminosity observed in local galaxies. Because the shorter Spitzer wavelengths sample the stellar bump at the redshifts of the submm sources, one can obtain a model independent estimate of the redshift, σ(Δz /(1 + z )) = 0.07. The median redshift of the secure submm counterparts is 2.0. Using X-ray and mid-IR imaging data, only 5% of the secure counterparts show strong evidence for an active galactic nucleus (AGN) dominating the IR luminosity. This thesis also presents deep Spitzer mid-IR spectroscopy of 13 of these SMGs in order to determine the contribution from AGN and starburst emission to the IR luminosity. I find strong polycyclic aromatic hydrocarbon (PAH) emission features in all of the targets, while only 2/13 SMGs have a significant mid-IR rising power-law component which would indicate an AGN. In the high signal-to-noise ratio composite spectrum of the SMGs I find that the AGN component contributes at most 30% of the mid-IR luminosity, implying that the total L[sub IR] in SMGs is dominated by star formation and not AGN emission. I also find that the SMGs lie on the relation between the luminosity of the main PAH features and L[sub IR] established for local starburst galaxies, confirming that the PAH luminosity can be used as a proxy for the star formation rate. Interestingly, local ULIRGs, which are often thought to be the low redshift analogues of SMGs, lie off these relations, as they appear deficient in PAH luminosity for a given L[sub IR]. In terms of an evolutionary scenario for IR luminous galaxies, SMGs are consistent with being an earlier phase in the massive merger (compared with other local or high redshift ULIRGs) in which the AGN has not yet become strong enough to heat the dust and dilute the PAH emission. I further investigate the overlap between high redshift infrared and submm populations using a statistical stacking analysis to measure the contribution of near- and mid-IR galaxy populations to the 850 μm submm background. For the first time, it is found that the 850 μm background can be completely resolved into individual galaxies and the bulk of these galaxies lie at z [Less-than sign over tilde] 3. Additionally I present a detailed study of the most distant SMG discovered to date, which I call GN20. This unusually bright source led to the discovery of a high redshift galaxy cluster, which is likely to be lensing the SMG. I discuss the potential for using bright SMGs in future submm surveys to identify high redshift clusters. Finally, for this complete sample of SMGs, I present the cumulative flux distribution at X-ray, optical, IR and radio wavelengths and I determine the depths at which one can expect to detect the majority of submm galaxies in future mm/submm surveys, such as with SCUBA-2, the successor to SCUBA.Science, Faculty of
Physics and Astronomy, Department of
Graduate
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Cole, Shaun. "Evolution of large scale structure and galaxy formation." Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315745.
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McCracken, Henry Joy. "Galaxy evolution in the William Herschel Deep Field." Thesis, Durham University, 1999. http://etheses.dur.ac.uk/4590/.
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In this Thesis we investigate the evolutionary histories of faint field galaxies using extremely deep optical and near-infrared photometry. Our work is centred on a 50 arcmin(^2) region at high galactic latitude which we call "The William Herschel Deep Field" (WHDF). In this work we describe three new near-infrared surveys of this field. In considering both this infrared data and the existing optical data, our broad aims are to increase our understanding of both the growth of galaxy clustering in the Universe and also to determine the star-formation histories of the field galaxy population. We consider our observations primarily in the context of luminosity evolution models in low density universes, but alternative scenarios are considered. Near-infrared galaxy counts derived from our catalogues are consistent with the predictions of our models, without the need for a steep faint-end slope for the galaxy luminosity function. We find that optical-infrared colour distributions of infrared-selected galaxies in the WHDF are deficient in red, early-type galaxies. This is consistent with the predictions of evolutionary models in which these systems have a small amount of on-going star-formation. We measure the amplitude of galaxy clustering in the WHDF for galaxies selected in optical and near-infrared bandpasses using the projected two-point correlation function. By comparing our measured clustering amplitudes with the predictions of our models we find that in all bandpasses the growth of galaxy clustering is approximately fixed in proper co-ordinates, again assuming a low-density Universe. Finally, an analysis of errors on the correlation function measurements suggest that discrepancies between our work and those of other authors may be explained by an underestimation of statistical errors.
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Ruggeri, Rossana. "Using galaxy surveys to understand the cosmological evolution." Thesis, University of Portsmouth, 2018. https://researchportal.port.ac.uk/portal/en/theses/using-galaxy-surveys-to-understand-the-cosmological-evolution(788a6c90-08a7-42e4-a509-30efab525982).html.
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Forthcoming galaxy redshift surveys are to a large extent motivated by the desire to obtain data on galaxy clustering so as to more accurately quantify the accelerating expansion of the Universe and thereby provide insight into the mechanism responsible for acceleration. Currently suggested mechanisms are: a cosmological constant, a new scalar field that contributes to the energy budget of the Universe as dark energy, and modification on the cosmological scale of the law of gravitation. It is also possible that the accelerating expansion of the Universe may only be properly understood by an as yet undeveloped alternative to the standard cosmological model. Because the large-scale distribution of galaxies is expected to follow a gaussian random field - for which statistical information is fully encoded in 2-point statistics, the key quantities provided by redshift surveys are the correlation function and its Fourier space analogue, the power spectrum. The detection of features due to baryonic acoustic oscillations (BAO) in these data will allow them to be used as standard rulers to reconstruct the expansion history of the Universe. In addition, the anisotropies (redshift-space distortions) induced by the velocities of galaxies on these correlators will provide a measurement of the growth rate of cosmic structures, and hence an independent probe of possible departures from the standard model. The power and scope of the forthcoming surveys (DESI and Euclid) will push measurements at least an order of magnitude beyond what is currently available, to provide unprecedented constraints on cosmological models. It is important therefore to refine the methods used to analyze the large data-sets being produced by these surveys. The investigations reported in this thesis contribute to this goal in several ways. The first part of this thesis describes the development of a faster method to measure the anisotropic clustering signal so as reduce computational load. In particular the measurement of line-of-sight-dependent clustering using fast Fourier transform routines is described, that results in an impressive increase in efficiency compared to standard pair-counting approaches. The second part is concerned with how best to combine data from different volumes within the surveys. Current analyses split the redshift range into separate bins and repeat the traditional analysis within each bin. However, this method is not only computationally expensive but also results in loss of information (ignoring galaxy pairs across different bins), and increased edge effects on large scales. An alternative approach is presented that applies weighting schemes to account for the redshift evolution of clustering. It is shown that the weightings act as a smooth window on the data, compressing the signal in the redshift direction with no theoretical loss of information. Subsequent development derived and optimum set of weightings to constrain the growth of structure from the redshift space distortions signal. The weighting technique was also applied to improve constraints on primordial non-gaussianity at large scales. The third part of this work describes the development and testing of an efficient algorithmic pipeline, developed to performthe analyses, including the development of faster new algorithms (incorporating the new weighting schemes) to measure the anisotropic signal. This part also discusses how to deal with survey geometry when considering redshift evolution in clustering. The final part describes the application of the pipeline to analyze eBOSS data. In particular the first constraint on growth rate evolution over an unprecedented volume (1 < z < 2), as covered by the DR14 quasars, is presented.
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Pascut, Aurelia. "Evolution of X-ray properties of galaxy groups." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/6235/.
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This thesis presents the results from the Chandra Deep Group Survey, a survey dedicated to find high redshift groups of galaxies in deepest observations available in the Chandra archive. The catalogue compiled from this survey contains 26 groups and 36 clusters with available redshifts, with largest redshift being 1.3. This sample has been used to investigate the evolution of the thermal state of the gas at the centre of groups and compare this evolution to that of clusters. Different parameters have been used to quantify the strength of cool cores and it has been showed that groups and clusters have similar evolution of their cool core properties. Both classes of systems have a wide spread in the cool core strength at low redshifts, which then narrows at high redshifts showing a lack of strong cool core systems.