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1
Brouillet, Nathalie. "Contenu moléculaire de galaxies en interaction : la galaxie spirale Messier 81 et le groupe de galaxies de M81." Bordeaux 1, 1989. http://www.theses.fr/1989BOR10619.
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La distribution et l'abondance du gaz atomique et moleculaire dans les galaxies permettent l'etude de leur histoire et de la formation stellaire. Nous nous sommes interesses a la galaxie spirale messier 81, qui est consideree comme un prototype ideal pour tester la theorie des ondes de densite. Nous avons decouvert la presence d'une emission co dans m81 et une cartographie etendue a revele une deficience moleculaire au centre ainsi qu'une distribution annulaire. Des observations a plus haute resolution spatiale nous ont aussi permis de comparer les distributions relatives du co et d'autres traceurs de bras spiraux. M81 etant le membre principal d'un groupe de galaxies nous avons etudie son interaction gravitationnelle avec ses 2 plus proches compagnons et nous avons cherche a simuler les distributions observees du gaz interstellaire
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Belfort, Patrick. "Proprietes infrarouges et optiques des galaxies iras : des galaxies normales aux galaxies a flambee." Paris 7, 1987. http://www.theses.fr/1987PA077184.
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Grace au satellite iras, on a decouvert un type de galaxies dont le rapport luminosite infrarouge sur bleue peut atteindre 100 ou plus; ces galaxies qu'on suppose subir des flambees de formation d'etoile sont l'objet de cette these. Un modele photometrique simple a ete construit pour rendre compte des proprietes ir lointain et optique de ces galaxies a flambees. La photometrie ccd d'un certain echantillon de galaxies iras a ete realisee pour tester le modele: l'accord modele-observation est satisfaisant et la force, ainsi que l'extinction des flambees ont pu etre estimees
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Belfort, Patrick. "Propriétés infrarouges et optiques des galaxies Iras des galaxies normales aux galaxies à flambée /." Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb37602748s.
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Snaith, Owain N. "The environment of galaxies and groups of galaxies." Thesis, University of Central Lancashire, 2011. http://clok.uclan.ac.uk/2931/.
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In this thesis, we employ two numerical tools - semi- analytical models and N-body plus hydrodynamical simulations of large scale structure and individual galaxies - to explore the underlying physics governing the formation and evolution of groups of galaxies, and the role of environment in generating polar structures around disk galaxies. Using phenomenological models of baryonic physics imposed upon large-scale dissipationless simulations of the Universe, semi-analytic models (SAMs) are one of the principal methods used to model large samples of model galaxies. We sought to examine the properties of groups of galaxies with a range of densities using SAMs applied specifically to the industry-standard Millennium Run; for this work, we make use of the well-known Munich and Durham models, and their descendants. We are especially interested in how group properties change as we change the linking length of our Friends- of-Friends group finder. We compare the group populations and richness in these models and compare them both with observations and high-resolution N- body simulations. This leads us to the conclusion that the Durham models produce a much larger population of compact objects than the Munich models. We also explore the group dynamics and morphology as a function of density. We compare the luminosity distributions of galaxy groups using publicly available SAMs in order to explore
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Gruel, Nicolas. "Nature et formation des galaxies : les galaxies compactes lumineuses." Observatoire de Paris, 2002. https://hal.archives-ouvertes.fr/tel-02071406.
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L’évolution de la luminosité infrarouge et de l’UV peut s’expliquer par une chute de la formation stellaire entre les décalages spectraux de 0. 4 à 1, c’est-à-dire depuis 7 à 10 milliards d’années. Cette chute est due à deux types de galaxies : les galaxies infrarouges et les galaxies compactes lumineuses. Au cours de cette thèse, j’ai particulièrement étudié un échantillon de spectres de ces galaxies compactes observées au VLT. Ces objets sont très importants : il y a environ 7 milliards d’années ces galaxies représentaient la population dominante. De plus, malgré leur petite taille, elles rayonnent de l’ordre de 100 fois plus d’énergie que les galaxies locales irrégulières auxquelles les études précédentes les ont assimilées du fait de leurs caractéristiques photométriques et dynamiques semblables. Pour quelques objets, il existe des images prises par le télescope spatial, elles montrent que la plupart de ces galaxies sont en interaction ou du moins possèdent une seconde composante à moins de 10 kpc. L’ensemble des indices réunis que ces objets pourraient être non pas les progéniteurs des galaxies naines compactes locales mais ceux des galaxies spirales<br>The evolution of the luminosity function in UV is related to the increase in the global star formation rate density up to z ~ 1. This increase is mainly due to two differents types of galaxies : the luminous infrared galaxies (LIRGs) and the luminous compacts galaxies (LCGs). In this thesis, I study a representative sample of LCGs using VLT and HST data at redshift 0. 4-0. 9. About 7 Giga years ago, these galaxies were the dominant galaxy population in number density. Despite their relative small size, they radiate near 100 times more energy than the population of star-forming Blue Compact Galaxies. Spectroscopic analysis show LCGs are composed of a mixed stellar populations, which includes at least : a young burst (less than 10 8 years) superimposed to an older population (more than 1 Giga year). HST images reveal these galaxies are often in interaction or have a multiple component at less than 10 kpc. Our study suggest that these objects may be the progenitors of today’s population of spirals galaxies
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Epinat, Benoit. "Des Galaxies Proches Aux Galaxies Lointaines: Etudes Cinématique et Dynamique." Phd thesis, Université de Provence - Aix-Marseille I, 2008. http://tel.archives-ouvertes.fr/tel-00413769.
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L'étude cinématique des galaxies locales et lointaines permet de contraindre les scénarios de formation et d'évolution des galaxies. Pour cela, la spectroscopie à champ intégral permet une étude détaillée de la cinématique des galaxies proches et fournit depuis peu des indices sur la cinématique des galaxies lointaines. Cette thèse s'appuie principalement sur l'utilisation de l'échantillon cinématique de galaxies locales GHASP. Cet échantillon de référence composé de 203 galaxies spirales et irrégulières de l'Univers local dans des environnements peu denses observées par interférométrie de Fabry-Perot autour de la raie Hα (6563 Å) est le plus grand échantillon de données Fabry-Perot à ce jour. Après un passage en revue des principes de l'interférométrie Fabry-Perot et des nouveautés apportées à la réduction des données Fabry-Perot, mon implication dans le développement du 3D-NTT, nouvel instrument utilisant deux Fabry-Perot est exposée de même que ma participation au projet de spectrographe à grand champ pour les ELT, WFSpec, dont l'objectif est l'étude de l'évolution des galaxies. Je présente dans une deuxième partie les données GHASP. Cet échantillon a été entièrement réduit et analysé à l'aide de nouvelles méthodes. L'analyse cinématique de l'échantillon à partir des cartes cinématiques 2D a été initiée en particulier avec l'étude de la distribution des halos de matière sombre, de la forme des courbes de rotation, de l'influence des potentiels barrés et de la dispersion de vitesses du gaz ionisé. Dans une troisième partie, cet échantillon local sert de point de référence pour l'étude de la cinématique des galaxies lointaines. L'échantillon GHASP est projeté à grand décalage spectral (z = 1.7) afin de déterminer les biais observationnels liés au manque de résolution spatiale des données cinématiques de galaxies lointaines obtenues par SINFONI, OSIRIS et GIRAFFE. L'analyse cinématique de nouvelles observations SINFONI y est également présentée, et l'ensemble des données cinématiques 2D de la littérature est mis en regard avec les résultats obtenus sur l'échantillon GHASP, mettant en évidence une évolution du support dynamique des galaxies avec le temps.
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White, David Allen. "The multiphase medium of elliptical galaxies and clusters of galaxies." Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240155.
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Epinat, Benoît. "Des galaxies proches aux galaxies lointaines : études cinématique et dynamique." Aix-Marseille 1, 2008. https://tel.archives-ouvertes.fr/tel-00413769v3.
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L’étude cinématique des galaxies locales et lointaines permet de contraindre les scénarios de formation et d’évolution des galaxies. Pour cela, la spectroscopie à champ intégral permet une étude détaillée de la cinématique des galaxies proches et fournit depuis peu des indices sur la cinématique des galaxies lointaines. Cette thèse s’appuie principalement sur l’utilisation de l’échantillon cinématique de galaxies locales GHASP. Cet échantillon de référence composé de 203 galaxies spirales et irrégulières de l’Univers local dans des environnements peu denses observées par interférométrie de Fabry-Perot autour de la raie Ha (6563 Å) est le plus grand échantillon de données Fabry-Perot à ce jour. Après un passage en revue des principes de l’interférométrie Fabry-Perot et des nouveautés apportées à la réduction des données Fabry-Perot, mon implication dans le développement du 3D-NTT, nouvel instrument utilisant deux Fabry-Perot est exposée de même que ma participation au projet de spectrographe à grand champ pour les ELT, WFSpec, dont l’objectif est l’étude de l’évolution des galaxies. Je présente dans une deuxième partie les données GHASP. Cet échantillon a été entièrement réduit et analysé à l’aide de nouvelles méthodes. L’analyse cinématique de l’échantillon à partir des cartes cinématiques 2D a été initiée en particulier avec l’étude de la distribution des halos de matière sombre, de la forme des courbes de rotation, de l’influence des potentiels barrés et de la dispersion de vitesses du gaz ionisé. Dans une troisième partie, cet échantillon local sert de point de référence pour l’étude de la cinématique des galaxies lointaines. L’échantillon GHASP est projeté à grand décalage spectral (z = 1. 7) afin de déterminer les biais observationnels liés au manque de résolution spatiale des données cinématiques de galaxies lointaines obtenues par SINFONI, OSIRIS et GIRAFFE. L’analyse cinématique de nouvelles observations SINFONI y est également présentée, et l’ensemble des données cinématiques 2D de la littérature est mis en regard avec les résultats obtenus sur l’échantillon GHASP, mettant en évidence une évolution du support dynamique des galaxies avec le temps<br>Kinematical studies of low and high redshift galaxies enables to probe galaxy formation and evolution scenarios. Integral field spectroscopy is a powerful tool to study with accuracy nearby galaxies kinematics. Recent observations also gives a new 2D vision of high redshift galaxies kinematics. This work mostly relies on the kinematical sample of galaxies GHASP. This control sample, composed of 203 local spiral and irregular galaxies in low density environments observed with Fabry-Perot techniques in the Ha line (6563 Å), is by now the largest sample of Fabry-Perot data. After a revue on Fabry-Perot interferometry and a presentation of new data reduction procedures, my implications on both 3D-NTT Fabry-Perot instrument and the wide field spectrograph project (WFSpec) for galaxy evolution study with the european ELT are developed. The second section is dedicated to GHASP data. This sample have been fully reduced and analysed using new methods. The kinematical analysis of 2D kinematical maps has been undertaken with the study of the dark matter distribution, the rotation curves shape, bar signatures and the ionized gas velocity dispersion. In a third section, this local reference sample is used as a zero point for high redshift galaxies kinematical studies. The GHASP sample is projected at high redshift (z = 1. 7) in order to disentangle evolution effects from distance biases in high redshift galaxies kinematical data observed with SINFONI, OSIRIS and GIRAFFE. The kinematical analysis of new SINFONI high redshift observations is also presented and high redshift data found in the literature are compared with GHASP projected sample, suggesting some evolution of the galaxy dynamical support within the ages
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Lima-Neto, Gastao Bierrenbach. "Formation de galaxies elliptiques et structure des amas de galaxies." Paris 7, 1993. http://www.theses.fr/1993PA077317.
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Le theme de cette these est l'etude de la formation et de la structure de galaxies elliptiques au sein de groupes et amas de galaxies. Cette etude se divise selon deux approches principales: l'analyse des proprietes physiques et morphologiques de deux amas de galaxies, abell 85 et 2199 ; et l'etude numerique de la formation de galaxies elliptiques par coalescence de galaxies spirales. Les amas de galaxies ont ete analyses a partir de cliches pris par le detecteur ipc a bord du satellite einstein dans le domaine de rayonnement x. Le gaz intra-amas responsable de l'emission x est suppose etre en equilibre avec le potentiel de l'amas et sert de traceur de ce dernier. En utilisant une technique d'ajustement des cliches par des images de synthese, il est possible de determiner le profil radial de densite du gaz emetteur ainsi que sa morphologie et la presence des sous-structures. En tirant profit des proprietes spectrales du detecteur, le profil de temperature du gaz est estime. L'etude de la formation de galaxies elliptiques se fait par le biais de simulations a n-corps, en utilisant un code en arbre et un code de somme directe sur un ordinateur massivement parallele. Trois classes de conditions initiales ont ete realisees: deux galaxies spirales de masse semblable placees soit en orbite circulaire, soit sur une trajectoire de collision de plein fouet ; des groupes de galaxies spirales en equilibre du viriel ; un effondrement sans collision d'un gaz froid. Les galaxies spirales suivent le modele de miyamoto & nagai a trois composantes bulbe, disque et halo. Les simulations ont ete suivies jusqu'a la formation d'un objet elliptique central en equilibre quasi-stationnaire. Les proprietes physiques et morphologiques de l'objet final des simulations sont confrontees a des modeles issus de la physique statistique appliquee a des systemes gravitationnels en equilibre. Les structures fines, variation de l'ellipticite, deformation et rotation des isocontours, ont ete comparees a des donnees observationnelles. Une modification de la mecanique newtonienne a ete aussi consideree dans le cadre de l'etude de la structure du gaz intra-amas
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Chemin, Laurent. "Cinématique et dynamique de galaxies spirales." Paris 6, 2003. http://www.theses.fr/2003PA066052.
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Karl, Simon. "The Antennae Galaxies." Diss., lmu, 2012. http://nbn-resolving.de/urn:nbn:de:bvb:19-140782.
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Cordey, R. A. "Nearby radio galaxies." Thesis, University of Cambridge, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356676.
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Millington, S. J. C. "Clusters of galaxies." Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382461.
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Wright, Susan Clare. "Blazar host galaxies." Thesis, University of Southampton, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243088.
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Guo, Quan. "Galactic satellite galaxies." Thesis, Durham University, 2013. http://etheses.dur.ac.uk/7354/.
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In this thesis, we investigate the luminosity functions (LFs) and projected number density profiles of galactic satellites around isolated primaries of differing luminosity. To this end, we develop a new method to select isolated galactic satellite systems using the Sloan Digital Sky Survey (SDSS) spectroscopic and photometric galaxy samples. For specific luminosity primaries, we are able to stack as many as ~ 50,000 galaxy systems to obtain robust statisitcal results. Based on these samples, we derive accurate satellite luminosity functions extending almost 8 magnitudes fainter than their primaries and accurate projected number densities profiles of satellites down to 4 magnitudes fainter than their primaries. Then, we determine how the satellite luminosity functions and projected number density profiles vary with both the properties of their satellites and their primaries. In addition, we find that the normalized profiles can be well fitted by the NFW profiles in most cases. The dependence of the NFW concentration parameters on the luminosity of the satellites and their primaries are explored. Inspired by the similar independent study, we also explore the dependence of estimates of satellite luminosity functions on two different background subtraction methods. We then measure these quantities for model satellites placed into the Millennium and Millennium II dark matter simulations by the GALFORM semi-analytic galaxy formation model for different bins of primary galaxy magnitude. We compare our model predictions to the data that we previously measured. The generally successful comparison of the GALFORM model with the SDSS data performed here provides a non-trivial validation of the assumptions and framework of this kind of modelling.
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Lewis, Alexander John Robert. "Ultra-red galaxies." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/33044.
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Dusty star-forming galaxies (DSFGs) are highly luminous (LFIR ≳ 10¹² L⊙), very distant (z ≳2.5) and ≳ 10x rarer then 'normal', NIR-selected (BzK), star-forming galaxies. Capable of producing a Mstars ≳ 10¹¹-M⊙ galaxy after a tburst ~ 100-Myr burst of late-stage, merger-induced star formation, DSFGs naturally provide extreme laboratories with which to study the formation and evolution of massive structures within the Universe. Thus far, however, theoretical models have struggled to reconcile the observed abundance and redshift distribution of these massive, dust-enshrouded galaxies that occupy the high-end tail of the galaxy stellar mass function. Therefore, it is of paramount importance, from an observational point of view, to both increase the number of known distant (z ≳ 4) DSFGs and to thoroughly explore their extreme environments in order to provide further constraints on such models. Thus, in Chapter 2 of this thesis, I report on efforts to substantially increase the number of distant DSFGs using the uniquely wide H-ATLAS imaging survey. I analysed a sample of 109, so-called 'ultra-red galaxies' selected via their red Herschel-SPIRE flux densities (σ500 > 3.5 and S500 < 100mJy) and flux-density ratios (S500/S250 > 1.5 and S500/S350 > 0.85). Ground-Based continuum imaging at ~ 850 μm with the JCMT and APEX telescopes allowed me to locate the dust peaks of these S500 ≳ 30-mJy ultra-red galaxies and derive a median photometric redshift of zphot = 3.66 (3.30-4.27, IQR) for them (assuming that they can satisfactorily be represented by a Tdust ~ 30-K template SED). Using 25 spectroscopically confirmed DSFGs with SPIRE flux densities matching this ultra-red criteria, I determined that these FIR photometric redshift estimates have a minimum intrinsic scatter of σ = 0.14(1 + zspec) and systematically under-estimate the spectroscopic redshifts below zspec ≲ 5. With over a third of these ultra-red galaxies lying above z > 4, I derived a space density of at least p ≈ 6 x 10⁻⁷Mpc⁻³ for this sample (assuming a tburst = 100-Myr burst of star formation), which is only a factor of 7x less numerous than that of the most massive (Mstars ≳ 10¹¹M⊙), compact, quiescent galaxies selected in the NIR at z ~ 3. Finally, although the space density of z > 4 ultra-red galaxies aligns very well with that of massive (MBH ≳ 10⁸M⊙) AGN at z > 6, none have yet to be uncovered within this sample to date. In the following chapter, I present wide images obtained with LABOCA of a sub-sample of 22, representative ultra-red galaxies to see if these galaxies are signposting over-dense regions in the early Universe, as might be expected if they were to evolve into the most massive, compact, quiescent galaxies at z ~ 0. This LABOCA ultra-red galaxy survey covers an area of ≈ 0.8 deg² down to an average r.m.s. of 3.9mJy beam⁻¹, with the five deepest images going ≈ 2x deeper still. I catalogue 86 galaxies detected above > 3.5σ870 surrounding these 22 ultra-red galaxies, which implies a δ ≈ 100 ± 30% over-density of S870 > 8.5-mJy (LFIR ≈ (7-30) x 10¹² L⊙) DSFGs when compared against LESS. Thus, I am 99.93% confident that these ultra-red galaxies are pinpointing over-dense regions in the Universe, and ≈ 95% confident that these regions are over-dense by a factor of at least ≥ 1.5x. Using the same template SEDs as in the previous chapter, I derived a consistent median photometric redshift of z = 3.2 ± 0.2 with an IQR of z = 2.8-3.6 for these ultra-red galaxies. I constrained the surrounding galaxies likely responsible for this over-density to within |∆z| ≤ 0.65 of their respective ultra-red galaxies. However, on average, I was only able to associate one surrounding galaxy to within |∆z| ≤ 0.5 of its respective ultra-red galaxy. These 'associated' galaxies are radially distributed within (physical) distances of 1.6 ± 0.5Mpc from their ultra-red galaxies, have median SFRs of vI≈ (1.0±0.2)x10³M⊙ yr⁻¹ (assuming a Salpeter stellar IMF) and median gas reservoirs of Mgas ~ 1.7 x 10¹¹M⊙. These candidate proto-clusters have average total SFRs of at least Ψ ≈ (2.3 ± 0.5) x 10³M⊙ yr⁻¹ and a space density of ~ 9 x 10⁻⁷Mpc⁻³, consistent with the idea that their constituents may occupy the centres of rich galaxy clusters seen today. Finally, in Chapter 4 of this thesis, I extracted Herschel-SPIRE photometry at the 850-μm positions of DSFGs detected within in the S2CLS and S2COSMOS imaging surveys. I then analysed the multi-wavelength environmental properties around a robust sample of 64 ultra-red galaxies selected via their 'ultra-red probability'. Similar to the findings in Chapter 3, I found that these ultra-red galaxies are preferentially located in over-dense regions extending over scales of ~ 5' (or ~ 2Mpc at z ~ 3). Furthermore, I found that these candidate, high-redshift proto-clusters have FIR total dust masses and total SFRs of Mdust ~ 10⁹M⊙ and Ψ ~ 10³M⊙ yr⁻¹, respectively. Ground-Based, optical/NIR imaging around a subset of 42 ultra-red galaxies shows a factor of ~ 5x increase in both the stellar mass and the (MB -MI )-colour of associated LBGs as the radial distance decreases from . 500 kpc - consistent with the emergence of a galaxy red sequence at z ~ 3. Furthermore, these data show a 1-σ increase in the fraction of 'green-valley' galaxies within scales of ~ 5' compared to the field - supporting the concept that red-sequence galaxies are appearing at a faster rate around ultra-red galaxies compared to the field. There is a sizeable contribution of Mstars ~ 10¹²M⊙ from these high-redshift LBGs within the environments of ultra-red galaxies. On average, I was able to associate ≈ 28 LBGs to a given ultra-red galaxy (~ 30x the number of associated DSFGs). Although these systems have average optical/NIR/FIR properties that are consistent with their evolution into present-day galaxy clusters with DM halos of mass Mhalo ~ 10¹⁴-10¹⁵M⊙, I am still likely missing a sizeable contribution from unassociated LBGs and DSFGs due to the large photometric redshift uncertainties for the ultra-red galaxies. Therefore, the results presented in this thesis should be regarded as firm lower limits on these environmental properties around ultra-red galaxies, which can now only be improved upon when spectroscopic data increases the accuracy of the photometric redshift estimates presented here.
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Reda, Fatma M. "Isolated elliptical galaxies." Swinburne Research Bank, 2007. http://hdl.handle.net/1959.3/20857.
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Thesis (Ph.D) - Swinburne University of Technology, Faculty of Information & Communication Technologies, 2007.<br>A thesis presented in fulfillment of the requirements of Doctor of Philosophy, Faculty of Information and Communication Technologies, Swinburne University of Technology, 2007. Typescript. Bibliography p. 109-118.
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GIOANNINI, LORENZO. "Dust across galaxies." Doctoral thesis, Università degli Studi di Trieste, 2018. http://hdl.handle.net/11368/2918677.
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In this thesis, we investigate the evolution of dust mass and chemical composition in different galaxies by means of new detailed chemical evolution models which account for the presence of dust. We adopt updated prescriptions for dust formation in Asymptotic Giant Branch (AGB) stars and Type II SNe, as well as for dust accretion and destruction in the interstellar medium (ISM). We predict in detail the evolution of the abundances of single elements both in the dust and in gas phase of the ISM, and distinguish the contributions from different sources during the galactic time.
We study the dust evolution in galaxies of different morphological type, i.e. dwarf irregulars, spirals, Milky Way-type and ellipticals: our model has proven to be very useful to study various dust properties such as dust mass, dust-to-gas (DG) ratio and chemical composition. In our approach, the main difference between galaxies is the star formation history: in ellipticals it is assumed a very fast and intense star formation rate, and this rate decreases going towards spirals, irregulars and smaller galaxies.
First, we compare our model predictions for a typical dwarf irregular galaxy with chemical abundances measured in Damped Lyman Alpha (DLA) systems. After having reproduced the abundances of volatile elements S and Zn (unaffected by the presence of dust), we study the depletion patterns of refractory elements (Si and Fe), which tend to be incorporated in the dust phase. Our study suggests that Fe and Si undergo a different history of dust formation and evolution and that Fe is mainly incorporated into iron-rich solid nano-particles, which may form by dust growth in the ISM. We also provide a new method, based on DLA column density measurements and the ratio between volatile and refractory elements, to give for the first time an estimate of the chemical abundance ratios inside dust grains. In this way, we try to disentangle the main dust constituents and predict their evolution: in particular, we focus on the fraction between silicates and metallic particles and between pyroxenes and olivines.
Concerning the Milky Way, we present the evolution (in space and time) of the DG ratio in the context of the galactic habitable zone, defined as the region with highly enough metallicity to form planetary systems capable of sustaining life. In this study, we provide theoretical prescriptions of the DG ratio and metallicity for models of planetary systems formation.
Then we focus our study on high redshift elliptical galaxies, and we try to disentangle the responsible processes for the sudden appearance of metals and dust observed in those objects. The first metals and dust appear very early since they are both produced by short living massive stars (core-collapse SNe), on the time-scales of few tenths of million years. In their initial burst of star formation, the metallicity can attain almost a solar value after one hundred million years and the same is true for dust, to which also AGB stars contribute on time-scales equal or larger than 30 million years.
Finally, we study the cosmic dust rate (CDR) across the Universe by assuming that the cosmic dust abundance results from the contribution of galaxies of different morphological type averaged in a unitary volume of the Universe. These galaxies are assumed to evolve in number density according to their weight in the luminosity function at different redshifts and different cosmological scenarios. Parallel to the CDR we compute the cosmic star formation rate (CSFR) as well as the cosmic rate of metallicity. Our predictions are extreme important to understand the roles of dust production, accretion and destruction in the CDR evolution. Our best scenario predicts a dust rate peak between 2<z<3 and reproduces the observed CSFR. Eventually, we estimate the comoving dust density parameter Ωdust and we find a good agreement with data for z<0.5.
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Koleva, Mina V. "Les populations stellaires des galaxies naines elliptiques." Thesis, Lyon 1, 2009. http://www.theses.fr/2009LYO10020.
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Le passé des galaxies est inscrit dans leurs populations stellaires. Les galaxies les plus nombreuses sont les naines elliptiques (dEs), survivantes de la construction hiérarchique des structures. Par conséquent, l’évolution de l’Univers peut être lue dans les populations de ces galaxies. Dans cette thèse, je présente et je valide une méthode efficace et précise pour étudier l’histoire de la formation stellaire et de l’enrichissement en métaux des systèmes stellaires en se servant de spectres intégrés le long de la ligne de visée. La méthode a été testée de manière extensive avec des spectres de 40 amas globulaires Galactiques et elle a été appliquée à un échantillon de 16 galaxies elliptiques naines d’amas et de groupes et à NGC 205. La comparaison entre les mesures des spectres intégrés et celles obtenues au moyen de diagrammes couleur-magnitude et de spectroscopie d’étoiles résolues montrent que: (1) Les mesures de métallicité faites sur des spectres intégrés ont une précision de 0.15 dex; (2) Les modèles spectroscopiques doivent être améliorés afin de prendre en compte les branches horizontales bleues et les vagabonds bleus, mais nous avons résolu ce problème en ajoutant des étoiles bleues ad hoc ; (3) Les différents modèles de spectres de population sont tr`es comparables du moment qu’ils utilisent des grandes bibliothèques stellaires. Encouragée, et rassurée, par les bons résultats j’ai étudié les populations de galaxies observées avec FORS au VLT. Les résultats les plus marquant sont: (1) Les premières étoiles des galaxies naines se sont formées dans l’Univers précoce (elles sont contemporaines des vieilles étoiles des amas globulaires) et la formation des galaxies naines est compatible avec le scenario de down-sizing pour la formation des galaxies. 40% de la masse stellaire des dEs s’est formée avant z=1; (2) les galaxies naines présentent généralement un gradient décroissant de la métallicité du centre vers l’extérieur. La métallicité décroit typiquement de 0.5 dex dans un rayon effectif. Ces gradients existent déjà dans la population vieille. Les simulations numériques les prédisent mais requièrent un temps plus long pour les établir, et les nouvelles observations vont permettre d’améliorer les modèles. L’étude de NGC 205, galaxie du Groupe Local de masse comparable, indique les mêmes caractéristiques, qui donc ne dépendent pas de l’environnement<br>The past of the galaxies is imprinted in their stellar populations. The most numerous galaxies in the Universe are the dwarf ellipticals (dEs), left-over of the hierarchical mass-assembly. Consequently, the evolution of the Universe can be read from the stellar populations of the dwarf elliptical galaxies. In this thesis I present and validate an accurate and efficient method to study the age and metallicity evolution in stellar systems using spectra integrated along the line-ofsight. It was extensively tested and validated on a library of 40 Galactic globular clusters and applied to a sample of 16 dwarf elliptical galaxies in cluster and group environments and to NGC 205. The comparison between the integrated light measurement and CMD estimates of the clusters age and metallicity shows that : (1) The metallicity estimations of the old stellar populations are accurate up to 0.15 dex ; (2) the models have to be improved to account for the blue-horizontal branchs and the blue stragglers stars, but this problem can be presently solved by adding ad’hoc blue stars to the models ; (3) the different synthesis models give similar results providing large libraries are used for the synthesis. Further, encouraged by the good results, I applied the full spectrum fitting to dwarf elliptical galaxies observed with FORS at the VLT. The most striking results are : (1) The small galaxies start to form stars in the early Universe (at similar ages like the ages of Galactic globular clusters) and their star formation history is in agreement with the down-sizing scenario of galaxy evolution. 40% of the stellar mass of dEs was formed before z=1 ; (2) The dwarf ellipticals have in general decreasing metallicity from the centre by typically 0.5 dex in one halflight radius. These gradients are already present in the old population. The numerical simulations predict them, but need a longer time to construct them. The new observations will allow to improve the models. The study of NGC 205, galaxy of the Local Group of a similar mass, indicate similar characteristics, suggesting that they do not depend on the environment
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Vázquez, Mata José Antonio. "Statistical characterization of galaxies in groups and isolated galaxies : Luminosity Function." Thesis, University of Sussex, 2016. http://sro.sussex.ac.uk/id/eprint/61394/.
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Evolution of galaxies is one of the most important topics in astronomy to understand how the universe has been evolving. In particular, galaxy groups are important because they are the observable equivalent of dark matter (DM) haloes, and thus offer a direct insight into the physics that has occurred in the DM haloes in the Universe up to the present day. Isolated galaxies are crucial for studying intrinsic and secular processes able to affect the structure, morphology, and dynamics of galaxies for obtaining clear relationships and correlations to be confronted with the model predictions. The main goal of this work is to characterize the GAMA G3Cv1 galaxy groups catalogue and the UNAM-KIAS catalogue of isolated galaxies by one of the most important statistical studies, the galaxy Luminosity Function (LF), that helps to constrain the models of formation and evolution of galaxies. LFs have been estimated for galaxies in groups and isolated galaxies. The LF for groups has been characterized by the physical properties of the groups (mass and velocity dispersion), the photometry (colour), the morphological type and eleven wavelengths from the far infra-red to the ultra violet. The LF estimated for the isolated galaxies is characterized by morphology and the colour in the five SDSS bands. The results obtained constrain more effectively the formation and evolution models of the universe than previous samples. The differences between both catalogues are presented in the conclusions. Additionally, the galaxy morphology is one of the no well understood problems in the galaxy evolution process to support the hierarchical model of formation of large objects. In this work, a classification based on the colour and concentration of light was considered. However, due to the low resolution of the images, the confidence of this classification was only ~60%.
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Maier, Christian. "Emission line galaxies from CADIS high redshift Lyman-[alpha] [Lyman-alpha] galaxies and metal poor galaxies at medium redshift /." [S.l. : s.n.], 2002. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB10358880.
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Secrest, Nathan J., Henrique R. Schmitt, Laura Blecha, Barry Rothberg, and Jacqueline Fischer. "Was 49b: An Overmassive AGN in a Merging Dwarf Galaxy?" IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/623232.
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We present a combined morphological and X-ray analysis of Was. 49, an isolated, dual-AGN system notable for the presence of a dominant AGN, Was 49b, in the disk of the primary galaxy, Was 49a, at a projected radial distance of 8. kpc from the nucleus. Using X-ray data from Chandra, the Nuclear Spectroscopic Telescope Array, and Swift, we find that this AGN has a bolometric luminosity of L-bol similar to 10(45) erg s(-1), with a black hole mass of M-BH = 1.3(-0.9)(+10)M(circle dot) . Despite the large mass, our analysis of optical data from the Discovery Channel Telescope shows that the supermassive black hole (SMBH) is hosted by a stellar counterpart with a mass of only 5.6(-2.6)(+4.9)M(circle dot), which makes the SMBH potentially larger than expected from SMBH-galaxy scaling relations, and the stellar counterpart exhibits a morphology that is consistent with dwarf elliptical galaxies. Our analysis of the system in the r and K bands indicates that Was. 49 is a minor merger, with the mass ratio of Was 49b to Was 49a between similar to 1:7 and similar to 1:15. This is in contrast with findings that the most luminous merger-triggered AGNs are found in major mergers and that minor mergers predominantly enhance AGN activity in the primary galaxy.
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Guo, Yicheng, David C. Koo, Yu Lu, John C. Forbes, Marc Rafelski, Jonathan R. Trump, Ricardo Amorín, et al. "STELLAR MASS–GAS-PHASE METALLICITY RELATION AT 0.5 ≤ z ≤ 0.7: A POWER LAW WITH INCREASING SCATTER TOWARD THE LOW-MASS REGIME." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/621237.
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We present the stellar mass (M-*)-gas-phase metallicity relation (MZR) and its scatter at intermediate redshifts (0.5 <= z <= 0.7) for 1381 field galaxies collected from deep spectroscopic surveys. The star formation rate (SFR) and color at a given M-* of this magnitude-limited (R less than or similar to 24 AB) sample are representative of normal star-forming galaxies. For masses below 10(9) M-circle dot, our sample of 237 galaxies is similar to 10 times larger than those in previous studies beyond the local universe. This huge gain in sample size enables superior constraints on the MZR and its scatter in the low-mass regime. We find a power-law MZR at 10(8) M-circle dot < M-* < 10(11) M-circle dot: 12 + log (O/H) = (5.83 +/- 0.19)+(0.30 +/- 0.02) log (M-*/M-circle dot). At 10(9) M-circle dot < M-* < 10(10.5) M-circle dot, our MZR shows agreement with others measured at similar redshifts in the literature. Our power-law slope is, however, shallower than the extrapolation of the MZRs of others to masses below 10(9) M-circle dot. The SFR dependence of the MZR in our sample is weaker than that found for local galaxies (known as the fundamental metallicity relation). Compared to a variety of theoretical models, the slope of our MZR for low-mass galaxies agrees well with predictions incorporating supernova energy-driven winds. Being robust against currently uncertain metallicity calibrations, the scatter of the MZR serves as a powerful diagnostic of the stochastic history of gas accretion, gas recycling, and star formation of low-mass galaxies. Our major result is that the scatter of our MZR increases as M-* decreases. Our result implies that either the scatter of the baryonic accretion rate (sigma((M) over dot)) or the scatter of the M-*-M-halo relation (sigma(SHMR)) increases as M-* decreases. Moreover, our measure of scatter at z = 0.7 appears consistent with that found for local galaxies. This lack of redshift evolution constrains models of galaxy evolution to have both sigma((M) over dot) and sigma(SHMR) remain unchanged from z = 0.7 to z = 0.
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Tenjes, P. "Models of regular galaxies." Tartu, Estonia : Tartu Ülikool, 1993. http://catalog.hathitrust.org/api/volumes/oclc/30612322.html.
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Salmi, Fadia. "Comprendre les modes de formation d’étoiles dans l’univers lointain." Thesis, Paris 11, 2012. http://www.theses.fr/2012PA112173/document.
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L'objectif de mon travail de thèse a consisté à tenter de comprendre quels sont les mécanismes principaux à l'origine de la formation d'étoiles dans les galaxies au cours des derniers dix milliards d'années. Alors qu'il avait été proposé dans le passé que le rôle des fusions de galaxies était dominant pour expliquer l'allumage de la formation d'étoiles dans les galaxies lointaines formant leurs étoiles à de très grands taux, des études plus récentes ont au contraire mis en évidence des lois d'échelles reliant le taux de formation d'étoiles des galaxies à leur masse stellaire ou masse de gaz. La faible dispersion de ces lois semblait être en contradiction avec l'idée d'épisodes stochastiques violents de formation stellaire liés à des interactions, mais plutôt en accord avec une nouvelle vision de l'histoire des galaxies où celles-ci sont nourries de manière continue en gaz intergalactique.Nous nous sommes particulièrement intéressés à l'une de ces lois d'échelles, la relation entre le taux de formation d'étoiles (SFR) et la masse stellaire des galaxies, appelées communément la séquence principale des galaxies à formation d'étoiles. Nous avons étudié cette séquence principale, SFR-M*, en fonction de la morphologie et d'autres paramètres physiques comme le rayon, la couleur, la clumpiness. Le but étant de comprendre l'origine de la dispersion de cette relation en lien avec les processus physiques responsables de cette séquence afin d'identifier le mode principal de formation d'étoile gouvernant cette séquence. Ce travail a nécessité une approche multi-longueurs d'ondes ainsi que l'utilisation de simulations de profils de galaxies pour distinguer les différents types morphologiques de galaxies impliqués dans la séquence principale<br>The goal of my PhD study consists at attempt to understand what are the main processes at the origin of the star formation in the galaxies over the last 10 billions years. While it was proposed in the past that merging of galaxies has a dominant role to explain the triggering of the star formation in the distant galaxies having high star formation rates, in the opposite, more recent studies revealed scaling laws linking the star formation rate in the galaxies to their stellar mass or their gas mass. The small dispersion of these laws seems to be in contradiction with the idea of powerful stochastic events due to interactions, but rather in agreement with the new vision of galaxy history where the latter are continuously fed by intergalactic gas. We were especially interested in one of this scaling law, the relation between the star formation (SFR) and the stellar mass (M*) of galaxies, commonly called the main sequence of star forming galaxies. We studied this main sequence, SFR-M*, in function of the morphology and other physical parameters like the radius, the colour, the clumpiness. The goal was to understand the origin of the sequence’s dispersion related to the physical processes underlying this sequence in order to identify the main mode of star formation controlling this sequence. This work needed a multi-wavelength approach as well as the use of galaxies profile simulation to distinguish between the different galaxy morphological types implied in the main sequence
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Owers, Matthew Scott Physics Faculty of Science UNSW. "The effects of merging and environment on galaxies and clusters of galaxies." Publisher:University of New South Wales. Physics, 2008. http://handle.unsw.edu.au/1959.4/42795.
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This thesis addresses two fundamental questions in astrophysics: (i) To what extent is environment a driver of galaxy evolution? And (ii) How does hierarchical structure formation affect the galaxy environment? The former is addressed by examining the environments of starburst galaxies, the latter by examining clusters undergoing major mergers with focus placed on the efficacy of ??cold fronts?? in identifying systems that have recently undergone a major merger - an essential first step to understanding their impact. For the first of these studies, the 2dFGRS was exploited to select large samples of starburst galaxies. These were used to derive measurements of the local and large-scale environments, clustering properties, and morphologies of starburst galaxies. It is found local environment is most germane in terms of a starburst triggering mechanism, with the starburst galaxies showing an excess of close (<20 kpc) neighbours with comparable luminosity/mass, while 20-30% exhibit a morphology consistent with them being involved in an ongoing tidal/merger interaction. On large scales (5-15 Mpc), the starburst galaxies were found to be much less clustered compared to the overall 2dFGRS population, and were not preferentially found in rich clusters with just over half residing in low to intermediate luminosity groups. However, in a number of cases, evidence for obvious local environmental influences was lacking, indicating starbursts can also be internally driven. For the latter study, the Chandra, archive was used to select a sample of clusters exhibiting ??cold front?? features. Selection required the presence of significant density jumps (>1.5 at the lower 90% CI) in the intracluster medium and for the gas on the denser side of the front to be cooler. From this sample, the clusters Abell 1201, Abell 2163, RXJ1720.1+2638, and Abell 3667 were targeted for comprehensive spectroscopic follow-up at optical wavelengths using the 3.9m Anglo Australian and 6.5m Multiple Mirror Telescopes. Using 321 spectroscopically confirmed members for Abell 1201, 550 for Abell 3667 and 491 for Abell 2163 it is shown that these clusters contain substructure which can be directly related to the cold fronts, whilst for 335 confirmed members in RXJ1720.1+2638 promising evidence exists for merger activity related to the cold front. Despite the range of different types of cold fronts and substructures detected, it is clear that cold fronts are robust signposts of merger activity.
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Prugniel, Philippe. "Galaxies en interaction et evolution dynamique des galaxies elliptiques de faible masse." Toulouse 3, 1989. http://www.theses.fr/1989TOU30044.
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Discussion de l'evolution des galaxies a partir d'observations et d'experiences numeriques. Un systeme de traitement d'image qui integre de nouvelles methodes d'analyse de donnees est developpe. Le role des rencontres gravitationnelles entre galaxies est envisage comme moteur de l'evolution morphologique et dynamique des galaxies elliptiques
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Cañameras, R., N. Nesvadba, R. Kneissl, B. Frye, R. Gavazzi, S. Koenig, Floc’h E. Le, M. Limousin, I. Oteo, and D. Scott. "Planck’s dusty GEMS." EDP SCIENCES S A, 2017. http://hdl.handle.net/10150/625826.
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We present an analysis of high-resolution ALMA interferometry of CO(4-3) line emission and dust continuum in the "Ruby" (PLCK_G244.8+54.9), a bright, gravitationally lensed galaxy at z = 3.0 discovered with the Planck all-sky survey. The Ruby is the brightest of Planck's dusty GEMS, a sample of 11 of the brightest gravitationally lensed high-redshift galaxies on the extragalactic sub-mm sky. We resolve the high-surface-brightness continuum and CO line emission of the Ruby in several extended clumps along a partial, nearly circular Einstein ring with 1.4 '' diameter around a massive galaxy at z = 1.5. Local star-formation intensities are up to 2000 M-circle dot yr(-1) kpc(-2), amongst the highest observed at high redshift, and clearly in the range of maximal starbursts. Gas-mass surface densities are a few x10(4) M-circle dot pc(-2). The Ruby lies at, and in part even above, the starburst sequence in the Schmidt-Kennicutt diagram, and at the limit expected for star formation that is self-regulated through the kinetic energy injection from radiation pressure, stellar winds, and supernovae. We show that these processes can also inject sufficient kinetic energy and momentum into the gas to explain the turbulent line widths, which are consistent with marginally gravitationally bound molecular clouds embedded in a critically Toomre-stable disk. The star-formation efficiency is in the range 1-10% per free-fall time, consistent with the notion that the pressure balance that sets the local star-formation law in the Milky Way may well be universal out to the highest star-formation intensities. AGN feedback is not necessary to regulate the star formation in the Ruby, in agreement with the absence of a bright AGN component in the infrared and radio regimes.
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Díaz, García S. (Simón). "Signatures of secular evolution in disk galaxies." Doctoral thesis, University of Oulu, 2016. http://urn.fi/urn:isbn:9789526213187.
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Abstract
In this thesis we shed light on the formation and evolution of disk galaxies, which often host a stellar bar (about 2/3 of cases). In particular, we address the bar-driven secular evolution, that is, the steady redistribution of stellar and gaseous material through the disk induced by the bar torques and resonances. We characterize the mass distribution of the disks in the Spitzer Survey of Stellar Structure in Galaxies (S4G, Sheth et al. 2010) and study the properties of the different stellar structure components and the interplay between them.
We use 3.6µm photometry for ~ 1300 face-on and moderately inclined disk galaxies to analyze the frequency, dimensions, orientations and shapes of stellar bars, spiral arms, rings, (ring)lenses, and barlenses (i.e. lens-like structures embedded in the bars). We calculate the strength of the bars in the S4G via ellipse fitting, Fourier decomposition of the galaxy images, and from the gravitational tangential-to-radial forces. We also estimate the stellar contribution to the circular velocity, allowing us to analyze the coupling between non-baryonic and stellar matter within the optical disk. We average stellar density profiles (1D), the disk(+bulge) component of the rotation curve, and stellar bars (2D) as a function of fundamental galaxy parameters.
We complement the study with integral-field unit kinematic data from Seidel et al. (2015b) for a subsample of 16 S4G barred galaxies. We quantify the bar-induced perturbation strengths in the stellar and gaseous disk from the kinematics, and show that they agree with the estimates obtained from the images. We also use Hα Fabry-Perot observations from Erroz-Ferrer et al. (2015) for 29 S4G disk galaxies to study the inner slope of the rotation curves.
We provide possible observational evidence for the growth of bars in a Hubble time. We demonstrate the role of bars causing the spreading of the disk and the enhancement of the central stellar concentration. Our observations support the idea that Boxy/Peanut bulges in face-on perspective manifest as barlenses, that are often identfied in early-type galaxies hosting strong bars, and some of them also as inner lenses. We find that the amount of dark matter within the optical disk scales with the total stellar mass, as expected in the ΛCDM models. We also confirm that the observed inner velocity gradient is correlated with the central surface brightness, showing a strong connection between the inner shape of the potential well and the central stellar density.
We show that disks and bars in early-type (T < 5 ≡ Sc) and late-type (T ≥ 5) disk galaxies, or alternatively in galaxies having total stellar masses greater or smaller than 1010M☉, are characterized by very distinct properties. Late-type disks are less centrally concentrated (many galaxies are bulge-less) and present a larger halo-to-stellar mass ratio, what probably affects the disk stability properties. The detection of bars in late-type galaxies is strongly dependent on the identification criteria. On average, bars in early-type spirals (T = 0 − 2) are longer (both in physical units and relative to the disk) and have larger density amplitudes than the intermediate-type spirals (T ≈ 5), and the bar lengths among the latest-types in the S4G are also larger. In comparison to earlier types, the bars in late-type systems show larger tangential-to-radial force ratios. This result holds even when the estimated dark halo effect is included.
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Knudsen, Kirsten K., Johan Richard, Jean-Paul Kneib, Mathilde Jauzac, Benjamin Clément, Guillaume Drouart, Eiichi Egami, and Lukas Lindroos. "[C ii] emission in z ∼ 6 strongly lensed, star-forming galaxies." OXFORD UNIV PRESS, 2016. http://hdl.handle.net/10150/621730.
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The far-infrared fine-structure line [C II] at 1900.5 GHz is known to be one of the brightest cooling lines in local galaxies, and therefore it has been suggested to be an efficient tracer for star formation in very high redshift galaxies. However, recent results for galaxies at z > 6 have yielded numerous non-detections in star-forming galaxies, except for quasars and submillimetre galaxies. We report the results of ALMA observations of two lensed, star-forming galaxies at z = 6.029 and z = 6.703. The galaxy A383-5.1 (star formation rate [SFR] of 3.2 M-circle dot yr(-1) and magnification of mu = 11.4 +/- 1.9) shows a line detection with L-[C II] = 8.9 x 10(6) L-circle dot, making it the lowest L-[C II] detection at z > 6. For MS0451-H (SFR = 0.4 M-circle dot yr(-1) and mu = 100 +/- 20) we provide an upper limit of L-[C II] < 3 x 10(5) L-circle dot, which is 1 dex below the local SFR-L-[C II] relations. The results are consistent with predictions for low-metallicity galaxies at z > 6; however, other effects could also play a role in terms of decreasing L-[CII]. The detection of A383-5.1 is encouraging and suggests that detections are possible, but much fainter than initially predicted.
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West, Andrew Alan. "HI selected galaxies in the Sloan Digital Sky Survey /." Thesis, Connect to this title online; UW restricted, 2005. http://hdl.handle.net/1773/5418.
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Bernadi, Mariangela. "Nearby Early-type Galaxies." Diss., lmu, 1999. http://nbn-resolving.de/urn:nbn:de:bvb:19-2055.
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Valiante, Elisabetta. "High-redshift infrared galaxies." Diss., lmu, 2008. http://nbn-resolving.de/urn:nbn:de:bvb:19-91747.
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Kroeker, Teresa Lynn. "Evolution of elliptical galaxies." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0012/NQ35211.pdf.
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Sheth, Ravi Kiran. "Gravitational clustering of galaxies." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320096.
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Crawford, John W. "Star formation in galaxies." Thesis, Queen Mary, University of London, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437102.
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Bunker, Andrew John. "Searches for distant galaxies." Thesis, University of Oxford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337592.
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Weadock, Julie Louise. "Intermediate redshift radio galaxies." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325935.
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Halliday, Claire. "Low luminosity elliptical galaxies." Thesis, Durham University, 1998. http://etheses.dur.ac.uk/4639/.
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Long-slit spectra for the photometric axes of a sample of 14 elliptical galaxies, predominantly low-luminosity ellipticals, in the Virgo cluster and in nearby groups, are studied to investigate the galaxy kinematical structure and stellar evolutionary history. To determine the galaxy kinematical structure, the shape of the line-of-sight velocity distribution (hereafter LOSVD) is measured using the Fourier Correlation Quotient method of Bender (1990), adopting the parametrisation of the LOSVD due to van der Marel and Franx (1993). This parametrisation enables the asymmetrical and symmetrical deviations of the LOSVD from a Gaussian function to be measured by the amplitudes H(_3) and H(_4) of the Gauss-Hermite series respectively. Rotation, velocity dispersion (σ), H(_3) and H(_4) are determined as a function of radius for both the major and minor axes of our sample. To summarise, LOSVD asymmetries were measured for the major axes of 12 galaxies which in the majority of cases have been interpreted as evidence for central disk-like components; evidence of both radial and tangential anisotropy were found from the measurement of H(_4); central decreases in σ are measured for 3 galaxies, which is interpreted as evidence that they have undergone some form of merger or interaction. On the basis of their measurements, galaxies are classified into 3 classes: types 1, 2 and 3. "Type 1" galaxies show strong evidence for both disk and bulge components and have the greatest measured values of H(_3) for our sample. Galaxies of "type 2" show strong evidence for embedded disk components and most (3 of 4) are measured to have central decreases in a. "Type 3" galaxies have kinematically-decoupled cores. Other galaxies, not classified, are NGC 3379 and NGC 4468.Measurements of the line-strength indices Mg(_b), Mg(_2), Hβ, Fe5270, Fe5335 and <Fe> are determined as a function of radius for all spectra and established to the Lick/IDS scale. The relations Mg’(_b)-Mg(_2), Mg’(_b), - log(σ), Mg(_b)- <Fe> and Hβ-[Mg(_b) <Fe>] are then studied. The Mg’(_b),-Mg(_2) relation of Wegner et al. (1998) and the calibrations of Worthey (1994) are compared with measurements here: this is used as a check of our calibration of Mg’(b), and Mg(_2). Measurements in the Mg’(_b)-log(σ) plane are considered separately for each galaxy and compared with the central relation of Colless et al. (1998). Measurements for most galaxies are found to be in good agreement with this relation. Measurements of Mg(_b) and <Fe> are similarly considered for each galaxy and compared with the predictions of the models of Worthey (1994). For the majority of galaxies, measurements are clearly offset from the Mg(_b)-<Fe> model grid of Worthey (1994), representing an [(^Mg)-(_Fe)] overabundance. This is an important result which shows that the [(^Mg)-(_Fe)] overabundance detected previously for the giant ellipticals similarly exists for ellipticals of the low luminosities studied here. For most galaxies this overabundance is found to be a constant function of radius. For the "type 2" galaxy NGC 3605, and NGC 4468, measurements are consistent with solar abundance ratios. Finally, measurements of Hβ and [Mg(_b) <Fe>] are compared with the models of Worthey (1994) to distinguish gradients in both age and metallicity. For all galaxies, gradients in metallicity are found with metallicity decreasing as a function of radius. For 5 galaxies (NGC 4564, NGC 3377, NGC 4478, NGC 4339 and NGC 3605) age gradients are also detected, with the galaxy centre shown to be younger than the surrounding galaxy. Interpreting these results together, different formation scenarios are proposed for the different galaxy types. For galaxies of "type 1", formation by homogenous, dissipational collapse is proposed. Galaxies of "type 2" show evidence for a less homogenous evolutionary history involving dissipationless collapse. No conclusive scenario is proposed for galaxies of "type 3".
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Wilkinson, David Adam. "Molecular hydrogen in galaxies." Thesis, Durham University, 1987. http://etheses.dur.ac.uk/6657/.
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This study aims to understand the key role played by molecular hydrogen in the evolution of galaxies, with a view to constraining its radial distribution in the Galaxy and the CO→H(_2) conversion factor α(_20).The star formation rate is shown to be correlated with the surface density of H(_2). A correlation between the molecular hydrogen fraction and the metallicity of a region allows the time evolution of H(_2) to be described. This leads to a modified 'Schmidt Law' of the SFR which explains quite naturally the production of galactic metallicity gradients and the constancy of the SFR in the absence of infall. A consistent closed model of the chemical evolution of the Galaxy is proposed to solve the G-dwarf problem, the stellar age-metallicity relation and the metallicity gradient, leading to the prediction of some initial amount of pre-disc processing of gas into visible and dark matter. It is found that a constant yield of metals is more appropriate than a yield proportional to metallicity. Possible time variations of the returned fraction, the dark matter fraction and the SFR are also studied. For consistency, we suggest that dark matter in the solar neighbourhood could be totally baryonic provided the Miller-Scalo IMF is modified at the lower end, that is, the dark matter resides in low mass stars or brown dwarfs. The production of metallicity gradients in spiral galaxies is shown to be a direct consequence of the radial variation of the total surface density of matter and the age of the disc. The role of molecular gas in the evolution of the Oort Cloud of comets is examined. It is shown that comet showers with a mean interval of ̴̱ 30My cannot be produced using perturbations of the Oort Cloud by known stars or molecular clouds. If there is indeed an apparent 30My periodicity in the terrestrial mass extinction and geological records, we argue that astronomically induced processes are unlikely to be the primary cause. Evidence is presented that the lifetime of the molecular gas phase is ≤ 2.lO(_8)y, and arguments, particularly from CO observations of the Virgo galaxy cluster, favouring longer lifetimes are shown to be not well founded. We suggest that the ICM in Virgo reduces the value of α(_20) as compared to isolated galaxies. From the above considerations, the radial distribution of in the Galaxy is derived and shown to agree in the inner Galaxy with that derived from ɤ-ray analysis. In the solar neighbourhood we find α(_20) = 2.5±0.5, and present evidence that α(_20) varies as a function of Galactocentric radius and from galaxy to galaxy.
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Huang, S. N. "Dynamics of interacting galaxies." Thesis, University of Manchester, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378332.
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Tadhunter, C. N. "Emission line radio galaxies." Thesis, University of Sussex, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379458.
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Cotter, Gary. "Distant giant radio galaxies." Thesis, University of Cambridge, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364574.
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Forbes, Duncan Alan. "Galaxies in the infrared." Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240127.
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Scott, Caroline. "Active and merging galaxies." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/24872.
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Galaxy close pairs are studied to investigate the effects of gravitational interactions on star formation and black hole accretion processes in merger progenitors. We derive star formation rates from near-ultraviolet luminosities; this is a new method for studying mergers and provides unique insight into recent star formation rates. A range of progenitor masses are considered, as well as the separation between merging galaxies and the environment they inhabit. Star formation enhancements in major versus minor close pairs are also considered. Pairs are extracted from the SDSS by identifying galaxies with small angular separation and small recessional velocity difference. Optical photometry in five filters is available for these galaxies. The pairs sample is cross-matched with near-ultraviolet flux measurements from GALEX and specific star formation rates are derived. We study the fraction of active galaxies as a function of separation in close pairs and seek observational evidence for merger activity triggering black hole accretion. Optical emission lines are used to identify progenitors harbouring active galactic nuclei, and the ratio of active galaxies in close pairs is compared to that of non-mergers. The variable properties of a sample of quasi-stellar objects (QSOs) are analysed. We present optimal QSO classification algorithms that exploit time series variability features calculated from Pan-STARRS light curves. This groundbreaking work crosses boundaries between astrophysics, statistics and machine learning. Spectroscopically confirmed QSOs and stars are used to train Support Vector Machine and Random Forest algorithms. We compare and evaluate the outcome of these models then apply them to Pan-STARRS light curves over nine medium deep fields, each covering 7 degrees-squared and located uniformly across the sky, to predict likely QSO candidates. We present a host of new variability features to characterise and provide measures of QSO variability.
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Williams, Michael J. "Early-type disk galaxies." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:936168ab-f49a-410a-9e1b-80c7ad7cf556.
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In this thesis I investigate the dynamics and stellar populations of a sample of 28 edge-on early-type (S0--Sb) disk galaxies, 22 of which host a boxy or peanut-shaped bulge. I begin by constructing mass models of the galaxies based on their observed photometry and stellar kinematics. Subject to cosmologically motivated assumptions about the shape of dark haloes, I measure in a purely dynamical way their stellar and dark masses. I make a preliminary comparison between the dynamically determined stellar masses and those predicted by stellar population models. I then compare the Tully-Fisher (luminosity--velocity) relations of the spirals and S0s in the sample. I show that S0s are systematically fainter at a given rotational velocity, but the amount by which they are fainter is less than expected by models in which they are the products of truncation of star formation in spirals. This raises the possibility that S0s are smaller or more concentrated than spirals of the same mass. I then study the vertical structure of the boxy and peanut-shaped bulges of a subset of the sample. Among this sample of five galaxies, I find one example in which the stellar populations show no evidence that the bulge and the disk formed in different processes, and in which the bulge is in perfectly cylindrical rotation, i.e. its line-of-sight velocity does not change with height above the disk. This galaxy is probably a pure disk galaxy. However, even with this small sample, I also show that cylindrical rotation and homogeneous stellar populations are not ubiquitous properties of boxy and peanut-shaped bulges. Finally I analyse central and radial trends in the stellar populations of the bulges of full sample of 28 galaxies. I find that, at a given velocity dispersion, the central stellar populations of these barred early-type disk galaxies are identical to those of elliptical galaxies, which suggests that secular evolution does not dominate the centre of these galaxies. However, the radial metallicity gradients are shallower than those of ellipticals. This is qualitatively consistent with chemodynamical models of bar formation, in which radial inflow and outflow smears out pre-existing gradients.
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Geen, Samuel Thomas. "Feedback in dwarf galaxies." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:70568e50-ff79-4c2a-a731-ce1826015b0d.
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Stellar feedback processes have been suggested as a mechanism for explaining various properties of galaxies, especially dwarf galaxies, which have weaker potentials and thus lower escape velocities for galactic winds. In this thesis, I present work done during my DPhil to better understand these processes. I begin by discussing the techniques used to simulate galaxies as collections of astrophysical fluids in a cosmolog- ical context, and present some methods for interpreting the results of such simulations. I then present two projects aimed at furthering our understanding of feedback in dwarf galaxies. The first project is the investigation of a suite of simulations of satellites of a Milky Way-class halo. We discuss the formation of high-redshift dwarf galaxies and the effect that supernova feedback and reionisation have on the gas content and star formation history of these objects. We find that neither process has a dramatic effect on the star formation rates in high redshift dwarf galaxies that have already begun forming stars prior to reionisation. We do find, however, that the population of satellites is dramatically altered by the presence of cooled gas in the host halo, which increases the tidal stripping of satellites that pass close to the host. The second project concerns detailed simulations of a 15 solar mass star throughout its evolution, studying photoionisation, wind and supernova feedback from this star in various environments. Preliminary results are given for these simulations, which are compared to the results of previous authors.
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SYGNET, J.-FRANCOIS. "Dynamique des galaxies spirales." Paris 7, 1989. http://www.theses.fr/1989PA077118.
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Etude de la dynamique de la composante stellaire des galaxies discoidales et des mecanismes d'instabilites a la base de la formation et de l'evolution des spirales et des barres en utilisant le concept spiral de densite considere comme le principal responsable de leur structure observee. On montre comment un traitement precis des equations fluides et de leur fermeture permet d'obtenir une relation de dispersion exacte pour les ondes spirales. Des simulations numeriques d'un modele de galaxie realiste sont ensuite etudiees. Un des problemes principaux de la theorie des ondes de densite est ensuite aborde: l'utilisation de methodes wkb qui interdit la description des spirales ouvertes et celle des spirales barrees
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Jones, Mark, Beverly J. Smith, and Mark Giroux. "Detached Tidal Dwarf Galaxies." Digital Commons @ East Tennessee State University, 2019. https://dc.etsu.edu/asrf/2019/schedule/127.
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Dwarf galaxies may form in the tidal tails of galaxy interactions. If these tidal dwarf galaxies (TDGs) detach from their parent galaxies, then an independent dwarf galaxy emerges. However, the lifespan of such objects is uncertain. Using IR, UV, and optical images, we conducted a search for detached TDGs from a set of 40 interacting galaxy pairs in the local Universe, and a control sample of 37 spiral galaxies. Both samples include 3.6 micron, 4.5 micron, 8 micron, and NUV images. In an earlier study (Smith et al. 2016), we used the IRAF daofind software (Stetson 1987) to search for star-forming regions within the main bodies of these galaxies and in their extended tidal tails. In the current study, we used the same procedure to search for such regions outside of the galaxies. We used two spatial scales to search for the TDGs, 1 kiloparsec and 2.5 kiloparsecs radius, and then used Spitzer infrared colors to identify and eliminate possible foreground stars and background quasars. The remaining objects may be detached tidal dwarfs that formed in the tails and then escaped. After comparing our observational results of the number of TDGs surrounding our interacting galaxies to the numbers around normal spirals, we find no significant difference in the number of candidate TDGs near interacting galaxy pairs compared to normal spiral galaxies. The most promising TDG candidates will be targeted by follow-up spectroscopic observations to determine their redshifts, metallicities, and their velocity structures. Younger TDGs are expected to have higher metallicities relative to their masses compared to primordial dwarf galaxies, relative to the standard mass-luminosity relationship for galaxies. Furthermore, TDGs should lack dark matter in contrast to primordial dwarf galaxies.
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Thompson, David Djorgovski S. G. "Surveys for primeval galaxies /." Diss., Pasadena, Calif. : California Institute of Technology, 1995. http://resolver.caltech.edu/CaltechETD:etd-10242007-142316.
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