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Dissertations / Theses on the topic 'Clusters of galaxies'
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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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Jeltema, Tesla Erin. "Cosmology with clusters of galaxies : high-redshift clusters and the evolution of cluster substructure." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/28372.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2004.Includes bibliographical references (p. 85).
Clusters of galaxies have become an important cosmological tool, yet we do not un-erstand many aspects of their formation and development. In this thesis, I pursue two projects aimed at using clusters to constrain cosmology and better understanding cluster evolution. First, I examine the Chandra observation of MS1054-0321. MS1054-0321 is the highest redshift cluster in the Einstein Medium Sensitivity Survey (EMSS), and it was one of the first high-redshift clusters observed with Chandra. I confirm that this cluster is hot and massive, although its temperature is slightly lower than inferred previously. I also detected an iron line in this cluster, one of the first detections of iron in a cluster at these redshifts, with an abundance consistent with early enrichment of the ICM. MS1054-0321 exhibits significant substructure, which I study in detail for the first time. In X-rays, it appears to be a nearly equal mass double cluster in the process of merging. Both the cluster galaxies and mass associated with the western subclump are offset from the X-ray peak, possibly indicating that the gas in the subclump is being stripped off as it falls into the cluster. Despite the lower temperature, I find that the detection of this cluster in the EMSS constrains Qm to be less than one.
(cont.) In the second project, I investigate the evolution of cluster substructure with redshift, quantifying for the first time cluster structure out to z [approx.] 1. My sample includes 40 X-ray selected, luminous clusters from the Chandra archive, and I quantify cluster morphology using the power ratio method (Buote & Tsai 1995). I find that, as expected qualitatively from hierarchical models of structure formation, high-redshift clusters have more substructure and are dynamically more active than low-redshift clusters. Specifically, the clusters with z > 0.5 have significantly higher average third and fourth order power ratios than the lower redshift clusters. This observation of structure evolution indicates that dynamical state may be an important systematic effect in cluster studies seeking to constrain cosmology, and when calibrated against numerical simulations, structure evolution will itself provide interesting bounds on cosmological models.
by Tesla Erin Jeltema.
Ph.D.
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De, Lucia Gabriella. "Evolution of Galaxies in Clusters." Diss., lmu, 2004. http://nbn-resolving.de/urn:nbn:de:bvb:19-25762.
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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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Piffaretti, Rocco. "Faraday rotation in clusters of galaxies." Zürich : ETH, Eidgenössische Technische Hochschule, 2000. http://e-collection.ethbib.ethz.ch/show?type=dipl&nr=17.
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Reblinsky, Katrin. "Projection effects in clusters of galaxies." Diss., lmu, 2000. http://nbn-resolving.de/urn:nbn:de:bvb:19-4153.
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Mora, Marcelo D. "Star clusters in unperturbed spiral galaxies." Diss., lmu, 2008. http://nbn-resolving.de/urn:nbn:de:bvb:19-92728.
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MacLaren, Ian. "Studies of distant clusters of galaxies." Thesis, Durham University, 1987. http://etheses.dur.ac.uk/6891/.
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A technique of constructing crude, low-resolution Spectral Energy Distributions (SEDs) for galaxies in distant clusters, using a set of intermediate bandwidth filters and a CCD detector, is developed which is capable of redressing many of the problems which have previously beset work in this field. The technique has been used to study galaxies in the distant clusters 0016+16 (z = 0.54) and Abell 370 (z = 0.37).These SEDs are then used to individually classify each object in the CCD field, ascribing both an estimated redshift and a galaxy type. The SEDs have been extended into the rest-frame ultraviolet (~ 270 nm) by imaging high redshift galaxies in blue passbands. Monitoring the behaviour of the Colour-Magnitude effect in the optical and -ultraviolet (uv) regions, indicates the presence of a new class of object which exhibits excess emission in the uv whilst having optical colours similar to nearby E/SO galaxies. The significance of this uv-excess is addressed by examining the available uv spectroscopy of nearby early-type galaxies obtained from observations carried out on the International Ul traviolet Explorer satellite. This study, in conjunction with a series of crude evolutionary models, leads to the conclusion that the uv-excess is most likely a manifestation of evolutionary differences in the spectral properties of galaxies at high redshifts, resulting from increased levels of star formation. Having developed such methods for using distant clusters of galaxies as evolutionary probes, a catalogue of candidate distant clusters is constructed from high contrast copies of deep 4m photographic plates. Finally, a series of possible future observations bcised on such a resource, combining a wide range of techniques, is outlined.
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Basson, J. F. "Cold gas in clusters of galaxies." Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596456.
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The intracluster gas has only been fully explored in the last decade or so with the launch of the ROSAT satellite in 1990, and more recently the Chandra and XMM-Newton satellites in 1999. The data obtained from these X-ray telescopes has provided significant information about the intracluster medium. In this thesis, a theoretical and numerical study of the nature of the ICM is undertaken. In particular the formation and influence of cold gas clouds and the effects of powerful FR-II radio sources are considered. Clusters are modelled as a multi-phase cooling gas in a dark-matter potential well. The formation of cold gas clouds through the thermal instability is studied, as is the effects of shocks on cold clouds. The latter is important because of the alignment effect which implies that the presence of a radio source increases the luminosity of the clouds. Radio sources which occur as a result of feedback from the accretion of the cooling intracluster gas onto a central AGN have a noticeable effect on the energetics of the cluster. Observationally, they manifest themselves as cavities in the X-ray emitting ICM. Whether they are capable of halting the inflowing cooling ICM depends on the relative powers of the cooling flow and radio source. The jets expand supersonically into the ICM, heating and dragging the cluster gas out of the potential well. As this shocked gas rises, it cools adiabatically. As it falls back inwards, it forms a layer of cooler gas around the cocoon. The ICM gas is thermally unstable, and the contact discontinuity will be Rayleigh-Taylor unstable provided that its deceleration does not exceed the gravitational force. Coupling between the Rayleigh-Taylor and thermal instability modes can occur, and it is found that the growth rate increases over the individual uncoupled rates when they are of the same order of magnitude. This could provide a mechanism for the information of cold clouds around this interface.
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Moore, Ben. "Groups, clusters and superclusters of galaxies." Thesis, Durham University, 1991. http://etheses.dur.ac.uk/6091/.
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Galaxies are observed in a diverse range of associations. Understanding the dynamical, statistical and clustering properties of aggregations of galaxies forms the main body of this thesis. On the smallest scale, we use a model for the Local Group to study the formation of a typical galaxy system and to understand the mass distribution within the Local Group. Our model is a binary system excised from numerical simulation of a Universe dominated by cold dark matter which has similar radial velocity and separation as M31 and the Milky Way. We find that the timing argument provides a reliable method for placing a lower limit to the mass of the Local Group. The anisotropy parameter of the particle orbits within the dark halos of CDM are predicted to radially biased. To reconcile the mass of the Milky Way with the predictions from the timing argument and the mass of our model halo, the satellites of our Galaxy must be on circularly biased orbits. The asymptotic values of the rotation curves of the two halos match very closely those of M31 and the Milky Way, as the halos come closer together the curves become very distorted. A simple treatment of gas within our model extends the rotation curves into the central regions of the halos. In our model, M31 and the Milky Way collide 2.5 Gyrs from the present time, a fraction of the current crossing time. Intermediate scales are probed using a statistical analysis of groups of galaxies identified using well defined selection criteria from the CfA redshift survey. The grouping algorithm is optimised using artificial galaxy catalogues constructed from N-body simulations which have similar low order correlations to the original survey. We develop a method of estimating the total luminosity of groups of galaxies identified within magnitude limited redshift surveys and use it to calculate the luminosity function of galactic systems. This statistic measures the abundance of gravitationally bound structures, independent of the detailed arrangement of the luminous material within them. We find that this function has a smooth transition from single galajdes to rich clusters. The distribution of group velocity dispersions shows a discontinuity at the transition between groups and rich clusters. The correlation function of groups is found to depend on the mass range of the sample, luminous groups are more strongly correlated than faint groups. We compare these results with predictions from the CDM model and have extended to intermediate scales the previous success of the model on galactic and cluster scales. On large scales we have used an all sky redshift survey of galaxies detected by IRAS to investigate the topology of the Universe to a depth of 200h(^-1) Mpc. Qualitatively, the distribution of galaxies out to this distance appears similar to a Gaussian density field with a sponge-like topology. High and low density regions are topologically similar and surfaces of constant density are interconnected. Quantitatively, we have used the genus-threshold density relation of Hamilton et al. to measure the slope of the power spectrum over a range of length scales between l0 (^-1) Mpc and 50h(^-1) Mpc. To constrain the slope of the power spectrum we used artificial "galaxy" catalogues constructed from N-body simulations and a variety of Monte-Carlo and bootstrap techniques. Our topological analysis is consistent with a spectrum of power-law form with n ~ -1 (in δk(^2) x k(^n)) over the range of scales considered. Values of n < -1.8 and n > 0 are strongly ruled out by our data. The inferred power spectrum of the distribution of IRAS galaxies is similar to the predicted mass spectrum in the standard cold dark matter model on scales <15 h(^-1) Mpc, but falls off less steeply on larger scales. This discrepancy is significant at over 2σ and implies that structure identified by IRAS galaxies is coherent over scales larger than expected from the CDM model.
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De, Filippis Elisabetta. "Clusters of galaxies in x-rays." Thesis, Liverpool John Moores University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275933.
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Siddiqui, Hassan. "ROSAT observations of clusters of galaxies." Thesis, University of Leicester, 1995. http://hdl.handle.net/2381/35783.
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Observations of four rich clusters of galaxies made using the Position Sensitive Proportional Counter (PSPC) instrument onboard the German Rontgensatellit (ROSAT) observatory were analysed. These data were complemented by ROSAT Wide Field Camera (WFC), Ginga and optical Automated Plate Measuring Machine (APM) information. Cluster properties, including the temperature profile, gas mass and total gravitational mass were investigated. Estimates for the mass deposition rates of central cooling flows, where appropriate, were made. Substructure was investigated using isophotal analysis and the employment of hardness ratios. The presence of central, intrinsic absorption, discovered previously in some similar clusters was confirmed. This is probably due to cold gas clouds. In the case of A2199, the WFC/PSPC data provided useful constraints to the partial covering fraction of these putative gas clouds. Abell 2142, which is classified in the optical as a binary cluster was shown to have a complex substructure. It is highly elliptical out to ~ 2 Mpc which can be explained in terms of a merger between two subclusters of differing sizes. The temperature and luminosities measured for A2218 and A1061, both of which have high velocity dispersions, indicate that these dispersion measurements are overestimated. Substructure is the most plausible explanation; spatial analysis supports this view. The galaxy density profiles obtained from the APM data were found to be consistent with the King approximation, and their luminosity functions were in reasonable agreement with the 'universal' Schechter model with a characteristic absolute magnitude of Bj = -21.6. Finally, the x-ray data showed that the gas mass fraction continues to rise with radius at the limit of detectability of ~ 2 Mpc. Including the optical data, the baryonic fraction at this radius is = 0.3. This result is difficult to reconcile with the universal fraction determined from standard cosmological nucleosynthesis models.
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Marshall, Philip James. "Bayesian analysis of clusters of galaxies." Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615701.
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Mora, Marcelo. "Star clusters in unperturbed spiral galaxies." kostenfrei, 2008. http://edoc.ub.uni-muenchen.de/9272/.
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Dennis, Taylor, and Beverly J. Smith. "Clumps and Clusters in Ring Galaxies." Digital Commons @ East Tennessee State University, 2018. https://dc.etsu.edu/asrf/2018/schedule/209.
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For a sample of collisional ring galaxies, archival Hubble Space Telescope images were used to compare individual star clusters and kpc-sized clumps of star formation to each other in a variety of ways. For each galaxy, instrument, and filter, the magnitude of the brightest cluster in a clump was compared to the magnitude of the entire clump, and the fraction of the flux of the clusters in a clump over the flux of the entire clump was calculated and compared to star formation rates. In addition, a cluster luminosity function for each galaxy was derived. Comparing the brightest cluster in a clump to the magnitude of the entire clump and the flux ratio to the star formation rate did not show any significant patterns. However, the α found for the galaxies tended to be much flatter than what had been found in previous research. The α found seemed to be affected by the size of the bin used in the luminosity function. Using this information, α could be calculated for other incredibly luminous galaxies to see if the trend of flatter α continues.
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Sartoris, Barbara. "Cosmological constraints with clusters of galaxies." Doctoral thesis, Università degli studi di Trieste, 2012. http://hdl.handle.net/10077/7738.
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2010/2011This Ph.D. Thesis is devoted to the derivation of cosmological constraints by using clusters of galaxies as probes. Clusters of galaxies provide potentially powerful means to measure the growth of cosmic structures, as well as excellent astrophysical laboratories. As such they have played an important role in establishing the current cosmological paradigm. On one hand, the results presented in this Thesis provide cosmological constraints from the best X-ray surveys of distant galaxy clusters available at present. On the other hand, the techniques developed to forecast constraints from future survey represent a flexible tool to optimize the design of future surveys of galaxy clusters to shed light on the content of the "Dark Sector" of the Universe and on the nature of gravity.
XXIV Ciclo
1983
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Sarron, Florian. "Galaxy clusters in the cosmic web Searching for filaments and large-scale structure around DAFT/FADA clusters Weak lensing study of 16 DAFT/FADA clusters: Substructures and filaments." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS366.
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En tant que structures liées les plus massives de l’univers, les amas de galaxies permettent d’étudier l’influence de l’environnement sur l’évolution des galaxies. Dans ce manuscrit, je présente AMASCFI, un algorithme de détection d’amas développé durant la thèse et utilise le catalogue d’amas obtenu à partir des décalages spectraux photométriques du relevé Canada France Hawaii Telescope Legacy Survey (CFHTLS) pour étudier le rôle des amas sur l’évolution des galaxies. Je démontre les bonnes performances d’AMASCFI sur Euclid et le CFHTLS à partir de données simulées. Je l’applique au CFHTLS pour lequel AMASCFI est pur à 90% et complet à 70% à z<0.7 et déduis une masse pour chaque amas détecté à partir de la richesse. J’étudie alors l'évolution en décalage spectral des fonctions de luminosité des galaxies (GLF) de type précoce (ETG) et de type tardif (LTG) à différentes masses d’amas. J’observe que la GLF des ETGs faibles décroît à grand décalage spectral, la séquence rouge (RS) étant déjà formée à z~0.7, mais enrichie par de faibles ETG à z<0.7. Cela peut être dû à la suppression de la formation stellaire (“quenching”) des LTG dans l’amas ou à l'accrétion de faibles ETG pré-traités dans des groupes en chute sur l’amas. Pour étudier le rôle de ce pré-traitement, je détecte les filaments de la toile cosmique avec la méthode de Laigle et al (2018) et montre qu’elle est bien valide à la précision du CFHTLS. En comparant les distances aux amas AMASCFI des ETG et des LTG dans les filaments, je conclue que les filaments doivent être le siège de “quenching”. Cela pourrait être dû à l’étranglement des galaxies dans les groupes de galaxies mais plus de preuves sont nécessairesAs the most massive bound structures in the universe, galaxy clusters are a powerful probe of the impact of environment on galaxy evolution. In this work, I present AMASCFI, a new cluster finder algorithm using photometric redshifts I developed during the PhD and use the cluster catalogue obtained on the Canada France Hawaii Telescope Legacy Survey (CFHTLS) to investigate the role played by clusters and their environment on galaxy evolution. We show the good performances of AMASCFI on Euclid and the CFHTLS using mock data. In particular AMASCFI is 90% pure and 70% complete to z<0.7 for the latter. We then apply AMASCFI to the CFHTLS T0007, and infer a mass for each detected cluster using richness as a proxy. Using our cluster catalogue, we study the redshift evolution of the galaxy luminosity functions (GLFs) of early-type (ETGs) and late-type (LTGs) galaxies at different cluster masses. We observe that the ETG GLF faint-end drops at high redshift, the red sequence (RS) being already formed at z~0.7, but enriched by faint ETGs at z<0.7. This could be due to quenching of LTGs in the cluster or accretion of faint ETGs pre-processed in infalling groups. To investigate the role of pre-processing, we use the method of Laigle et al (2018) to detect filaments from photometric redshifts and show that it allows to recover the 3D cosmic web at CFHTLS accuracy. We apply it to the CFHTLS and detect filaments around AMASCFI clusters. Studying the distances of ETGs and LTGs in these filaments to clusters, we conclude that some quenching occurs in filaments. We suggest that this might be due to strangulation in galaxy groups though we still lack conclusive evidence for such a mechanism
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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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Clarke, Tracy E. "Probing magnetic fields in clusters of galaxies." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ50043.pdf.
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Lefebvre, Dominic. "Microwave background anisotropies from clusters of galaxies." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318046.
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Dalton, Gavin Bruce. "A survey of rich clusters of galaxies." Thesis, University of Oxford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314836.
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Stott, John Philip. "The evolution of galaxies in massive clusters." Thesis, Durham University, 2007. http://etheses.dur.ac.uk/2287/.
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We present a study of the evolution of galaxies in massive X-ray selected clusters across half the age of the Universe. This encompasses galaxies on the red sequence from the Brightest Cluster Galaxy (BCG) to the faint red population. We begin at the tip of the red sequence with an investigation into the near infrared evolution of BCGs since z =1. By comparing the BCG Hubble diagram and near-infrared colour evolution to a set of stellar population and semi-analytic models we constrain the evolution and formation redshift of these massive galaxies. Moving down in luminosity from the BCG, in chapter 3 we study the build up of the red sequence in massive clusters. To achieve this we compare the luminosity functions for red galaxies in a homogeneous sample of ten X-ray luminous clusters at z ~ 0.5 to a similarly selected X-ray cluster sample at z ~ 0.1. We quantify this result by measuring the dwarf to giant ratio to ascertain whether faint galaxies have joined the red sequence over the last 5 Gyr. In chapter 4 we study the evolution of the red sequence slope in massive clusters from z=l to present day. We compare our observed slope evolution to that predicted from semi- analytical models based on the Millennium simulation. We also look for trends between the red sequence slope and other cluster observables, such as X—ray luminosity, to investigate whether this will effect cluster detection methods which search for a colour-magnitude relation. In the final science chapter we present the details of our own cluster detection algorithm. This simple algorithm is based on finding clusters through the near-infrared and optical properties of the red sequence, drawing on our galaxy cluster evolution research. We describe the application of the algorithm to object catalogues from the UKIDSS DXS fields in order to find clusters at z ~ 1. To confirm the presence of the clusters we employ deep multi-object spectroscopy on the photometric members. The clusters found in this study are fed back into the high redshift regime of our galaxy evolution research.
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Kay, Scott Thomas. "Modelling the properties of galaxies and clusters." Thesis, Durham University, 2000. http://etheses.dur.ac.uk/4246/.
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This thesis examines various properties of galaxies and clusters within hierarchical models of structure formation. A simple model based on analytical scaling relations is applied to X-ray observations of clusters at low and high redshift, in an attempt to constrain cosmological parameters from their evolutionary properties. It is found that the density parameter, Ωo cannot be constrained using the data alone. Two independent constraints on the slope of the linear power spectrum, infer values of Ωo < 0.7 at 95 per cent confidence. The remainder of this thesis concentrates on the method of cosmological simulation, a self- consistent approach to the modelling of structure in the Universe. A parameter-space study is performed for the simplest model of galaxy formation: the radiative cooling of baryons within the cores of dark matter haloes. It is found that the properties of the galaxies in the simulations are insensitive to the range of parameters studied, with the exception of those that affect the cooling rate of the gas. For modest resolution and reasonable choices of physical parameters, the amount of baryons in galaxy material is around a factor of 2 too high. An investigation is then performed for including the effects of star formation and energy from supemovae (feedback) within cosmological simulations, to reduce the amount of gas that cools. The star formation rate is driven by the minimum density for which the stars formation occurs and, for high star formation efficiencies, is limited by the cooling rate of the gas. A successful model for feedback is found to require the prevention of reheated gas from cooling for a short period of time, as an attempt to mimick the properties of a multiphase medium. Finally, preliminary results are presented for simulations of a galaxy cluster, including the effects of radiative cooling, star formation and feedback. The properties of the cluster are found to vary significantly between models with and without feedback, due to the feedback reducing the star formation rate by reheating gas that cools.
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Smail, Ian Robert. "Gravitational lensing by rich clusters of galaxies." Thesis, Durham University, 1993. http://etheses.dur.ac.uk/10489/.
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We present observations and analysis of gravitationally lensed systems designed to test the usefulness of gravitational lensing as a probe into the nature of faint galaxies (B(_j) ≤ 27). The analysis techniques used also provide unique observational constraints on the masses and morphologies of the lensing clusters. Using a catalogue of giant arc candidates constructed with a well determined selection function we initially examine the possible uses of such a catalogue to provide information on the redshift distribution of galaxies to B(_j) ~ 26. We conclude that the extreme sensitivity of the lensing signal to slight differences in the lensing clusters prevents the successful application of this technique. Nevertheless, we show that the tests could be successfully applied to very deep observations of a single rich cluster. We then illustrate the uniquely detailed view of high redshift galaxies which is provided by giant gravitational arcs by presenting near-infrared imaging of a complete sample of spectroscopically-confirmed giant arcs. Spectral modelling of the multi-band colours of these arcs confirms that the most distant arcs (z ~1) are remarkably blue at all wave lengths. This observation is incompatible with models for the arc's colours which contain recent star bursts superimposed upon even moderate fractions of underlying evolved stel-lar populations. We conclude that a constant star formation rate in marginally sub-L* systems is most consistent with the observations of the z ~ 1 arcs. Using very deep optical images of three moderate and distant redshift clusters selected on either X-ray luminosity or optical richness (C11455+-22; z = 0.26, C10016+16; z = 0.55 and C11603-+43; z = 0.89) we create robust samples of faint galaxies (B(_j) ≤ 27) suitable for lensing studies. These samples are used in two separate analytic methods to study both the redshift distribution of the faint field galaxy population and the mass in the lensing clusters. Relatively simple tests rule out redshift distributions for the faint field galaxies which depart significantly, at either low or high redshift, from the no evolution prediction. The mass analysis uses newly-developed techniques to reconstruct for the first time the two dimensional mass distribution in the lens from the gravitationally distorted images of galaxies seen through the clusters. We conclude that the morphology of the mass distribution is accurately traced by the cluster galaxies. Finally, we present the discovery of a very wide separation multiply-imaged system recently found in deep Hubble Space Telescope images of the rich cluster AC114 (z = 0.31). Spectroscopic observations of the multiply imaged system confirm its lensed nature and provide a probable redshift of z = 1.87 for the source. Preliminary modelling of the cluster mass using all the gravitationally lensed galaxies in the field support the conclusions reached above - the cluster galaxies appear to be fair tracers of the mass.
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Rowley, David R. "Formation and evolution of clusters of galaxies." Thesis, University of Sussex, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.412670.
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Edge, Alastair Clouston. "X-ray emission from clusters of galaxies." Thesis, University of Leicester, 1989. http://hdl.handle.net/2381/35873.
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Clusters of galaxies are the largest gravitationally bound systems known. The study of clusters can therefore provide information on the distribution of matter in the Universe on the largest scales. The X-ray emission from clusters is of particular interest, as the gas held within the gravitational potential well of a cluster responds to the total mass ('Dark' and 'Visible') of that cluster. This thesis is based upon a sample of 44 observations of clusters made by EXOSAT which provided both imaging and spectral data. The data give well determined luminosities, temperatures, iron abundances and mass flow rates for these clusters. The results provide constraints on models for cluster dynamics and formation. The theoretical models and previous observations of clusters are reviewed in Chapter 1, concentrating on the X-ray domain. The results from the imaging telescopes and proportional counters are given in Chapters 2 and 3. Detailed observations of Virgo, Coma and Perseus are described in Chapter 4. A correlation analysis of the X-ray, optical and radio results is presented in Chapter 5. The implications of these correlations are discussed in Chapter 6. The thesis concludes with a brief look forward to future missions.
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Wilcox, Harry. "Constraining gravity models with clusters of galaxies." Thesis, University of Portsmouth, 2016. https://researchportal.port.ac.uk/portal/en/theses/constraining-gravity-models-with-clusters-of-galaxies(e6fa2dcf-2c33-4ae1-85ac-316dc84e31dd).html.
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An accepted explanation for the accelerated expansion of the late-time Universe is to modify the Einstein equation, either by adding a component to the energy-momentum tensor via dark energy, or to the Einstein tensor via a modification to gravity. The second of these options often involves the introduction of a scalar field, which couples to the matter components of the Universe and gives rise to a fifth force, of the same order of magnitude as gravity. Through a variety of experiments and astronomical observations, this fifth force has been demonstrated to be negligible on Terrestrial and Solar System scales. Therefore if it does act on large scales, it must be suppressed, or `screened', on small scales. In this thesis, I place constraints upon one of these screening methods, chameleon gravity. Chameleon gravity postulates the existence of a scalar field that couples with matter to mediate a fifth force. If it exists, this fifth force would influence the hot X-ray emitting gas filling the potential wells of galaxy clusters. However, it would not influence the cluster's weak lensing signal. Therefore, by comparing X-ray and weak lensing profiles, upper limits can be placed on the strength of a fifth force. To do so I first present two hydrodynamical simulations, one evolved under CDM+GR and the other under f(R). From these two simulations I generate X-ray surface brightness and weak lensing profiles for a number of simulated clusters. Using these profiles I test many of the assumptions of the technique used to constraint IfR0I. I then use these profiles to test the analytic pipelines developed to constrain f(R) gravity by applying a full MCMC analysis. From doing so I find constraints on the modified gravity parameters of IfR0I< 8:3 x10-5. Next I outline the creation of a sample of 58 clusters, including 12 new to the literature, with high quality weak lensing data from CFHTLenS and X-ray data from XCS. By stacking these clusters I use a multi-parameter MCMC analysis to constrain the two chameleon gravity parameters ( ß and φ∞). The fits are consistent with general relativity, not requiring a fifth force. In the special case of f(R) gravity (where ß = √1/6), I set an upper limit on the background field amplitude today of IfR0I< 6 x 10-5 (95% CL). This is one of the strongest constraints to date on IfR0I on cosmological scales. These fits are also found to be consistent with those recovered from the f(R) simulations. Finally I look at the future of this method, beginning with forecasting the constraints that this technique will be able to place on f(R) gravity using the Dark Energy Survey, finding IfR0I> 2 x 10-5. Next I discuss how the X-ray surface brightness profiles might be improved by removing contaminating point sources from the X-ray images and find that doing so leads to a reduction in the error bars of 5%. I end this thesis by detailing how the techniques discussed within can be applied to constrain other modified gravity theories, namely the Vainshtein mechanism. Doing so I am able to place competitive constraints upon Vainshtein gravity, including the first ever constraint on a particular parametrisation.
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Unewisse, Anne Margaret. "Radio emission from southern clusters of galaxies." Thesis, The University of Sydney, 1993. https://hdl.handle.net/2123/26671.
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Radio, optical, far-infrared and X-ray sources lying towards galaxy clusters listed in the southern portion of the Abell, Corwin and Olowin rich cluster catalogue (ACO) are presented. The bulk of the observational work is a radio survey of 39 nearby (distance class D < 3) southern ACO clusters undertaken at 843MHz with the Molonglo Observatory Synthesis Telescope. Also included are studies of 408MHz MRC radio sources and 60 pm IRAS far-infrared sources in the direction of ACO clusters.
The survey results are presented in two forms:
i) as a series of radio images, centred on each surveyed cluster with optical images from
the COSMOS database superimposed and IRAS far-infrared and Einstein X-ray
source positions marked, and
ii) in a table of positions, flux densities and optical identifications of the 682 radio
sources detected within the projected boundaries of the cluster sample.
The 207 optical identifications, 50 non-stellar IRAS sources and 20 Einstein sources falling
in the mapped regions are outlined in individual tables. Supplementary Very Large Array
and Australia Telescope Compact Array observations of selected sources are also presented.
The main results of the thesis are:
i) the number of far-infrared sources detected in the direction of a given cluster sample
depends on both the median redshift of the sample and the number of gas rich
galaxies in the clusters,
ii) the fractional radio luminosity fimction (RLF) of first ranked cluster galaxies is found
to flatten at a radio power of around log P(843) = 23 which corresponds power gap
in the differential RLF and an abrupt change in radio morphology, y
iii) a comparison with the RLF of a sample of non-cluster ellipticals suggests that, for
log P(843) > 23, first ranked cluster members are more likely to produce radio
emission than field galaxies and
iv) the radio—infrared correlation appears to hold regardless of cluster membership.
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Pierce, Michael John. "Spectroscopy of extra-galactic globular clusters." Australasian Digital Thesis Program, 2006. http://adt.lib.swin.edu.au/public/adt-VSWT20070731.104253/index.html.
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Thesis (Ph.D) - Swinburne University of Technology, Faculty of Information & Communication Technologies, 2006.A dissertation presented in fulfilment of the requirements of for the degree of Doctor of Philosophy, Faculty of ICT, Swinburne University of Technology, 2006. Typescript. Bibliography p. 90-99.
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Fellhauer, Michael. "Could merged massive stellar clusters build up a dwarf galaxy ? /." Aachen : Shaker Verl, 2001. http://catalogue.bnf.fr/ark:/12148/cb37739238k.
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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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Harris, William E., Stephanie M. Ciccone, Gwendolyn M. Eadie, Oleg Y. Gnedin, Douglas Geisler, Barry Rothberg, and Jeremy Bailin. "GLOBULAR CLUSTER SYSTEMS IN BRIGHTEST CLUSTER GALAXIES. III. BEYOND BIMODALITY." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/622870.
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We present new deep photometry of the rich globular cluster (GC) systems around the Brightest Cluster Galaxies UGC 9799 (Abell 2052) and UGC 10143 (Abell 2147), obtained with the Hubble Space Telescope (HST) ACS and WFC3 cameras. For comparison, we also present new reductions of similar HST/ACS data for the Coma supergiants NGC 4874 and 4889. All four of these galaxies have huge cluster populations (to the radial limits of our data, comprising from 12,000 to 23,000 clusters per galaxy). The metallicity distribution functions (MDFs) of the GCs can still be matched by a bimodal-Gaussian form where the metal-rich and metal-poor modes are separated by similar or equal to 0.8 dex, but the internal dispersions of each mode are so large that the total MDF becomes very broad and nearly continuous from [Fe/H] similar or equal to-2.4 to solar. There are, however, significant differences between galaxies in the relative numbers of metal-rich clusters, suggesting that they underwent significantly different histories of mergers with massive gas-rich halos. Last, the proportion of metal-poor GCs rises especially rapidly outside projected radii R >= 4 R-eff, suggesting the importance of accreted dwarf satellites in the outer halo. Comprehensive models for the formation of GCs as part of the hierarchical formation of their parent galaxies will be needed to trace the systematic change in structure of the MDF with galaxy mass, from the distinctly bimodal form in smaller galaxies up to the broad continuum that we see in the very largest systems.
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Rostagni, Florent. "Classification morphologique d'un échantillon optique d'amas de galaxies." Thesis, Nice, 2014. http://www.theses.fr/2014NICE4055/document.
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Les amas de galaxies sont l'une des sondes cosmologiques permettant de contraindre les modèles d'univers, via leur fonction de masse et leur vitesse de croissance, elles-mêmes mesurées par l'état dynamique des amas. Les grands relevés présents et futurs permettent d'avoir accès à une information plus nombreuse et plus complète sur les amas de galaxies et donc d'utiliser de nouvelles méthodes de détermination de leur état dynamique. Dans cette thèse, une nouvelle méthode de caractérisation morphologique 2+1D des amas a été développée afin d'établir une nouvelle classification des amas. Il s'agit d'une méthode optique basée sur la position et la vitesse radiale des galaxies. Les structures dans la zone d'influence des amas sont détectées et caractérisées en projection et dans l'espace des vitesses radiales à l'aide d'une analyse en ondelettes. À partir du nombre de structures, les amas sont classés en amas unimodal, bimodal ou multimodal. L'ellipticité de leur distribution projetée et la gaussianité de la distribution des vitesses radiales sont également utilisées pour raffiner la classification. La méthode de caractérisation et de classification morphologique a été appliquée à un sous-échantillon de 403 amas issus du catalogue C4 en utilisant les données du SDSS. Il en est ressorti que 25% des amas sont unimodaux, 33% sont bimodaux et 42% sont multimodaux. Une analyse de la stabilité de la classification a également été réalisée ainsi qu'une comparaison avec les résultats de la littérature, que ce soit d'un point de vue statistique ou au niveau des amas individuelsClusters of galaxies are one of the main cosmological probes used to constrain the cosmological parameters, through their mass function and their growth rate. The measure of these two quantities require the determination of the dynamical state of clusters. The present and future large and deep sky surveys give access to a more complete information on clusters and legitimate the development of new methods of determination of their dynamical state. In this thesis, a new method of characterization of the cluster morphology has been developed. It is a 2+1D method using galaxies and it enables to develop a new morphological classification of clusters. Structures around clusters are detected and characterized in projection and along the line of sight using a wavelet analysis. The new classification consists in counting the number of structures in the vicinity of clusters, three clusters classes were defined : unimodal, bimodal and multimodal. The ellipticity and the Gaussianity of the distribution of radial velocities are also used to refine the classification. The method was applied to a subsample of 403 clusters from the C4cluster catalogue using data from the SDSS. The results are : 25% of the clusters are unimodals, 33% are bimodals and 42% are multimodals. The stability of the classification with respect to the different parameters used was also performed as well as a comparison with the results from other studies in the literature
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Zibetti, Stefano. "Diffuse stellar components in galaxies and galaxy clusters." Diss., lmu, 2004. http://nbn-resolving.de/urn:nbn:de:bvb:19-30331.
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Schäfer, Björn Malte. "Methods for detecting and characterising clusters of galaxies." Diss., lmu, 2005. http://nbn-resolving.de/urn:nbn:de:bvb:19-40652.
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Makiya, Ryu. "Cosmic-Ray Acceleration in Galaxies and Galaxy Clusters." 京都大学 (Kyoto University), 2013. http://hdl.handle.net/2433/175125.
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Barger, Amy Josephine. "The morphological evolution of galaxies in distant clusters." Thesis, University of Cambridge, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627567.
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D'Eugenio, Francesco. "Kinematics and shapes of galaxies in rich clusters." Thesis, University of Oxford, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.665490.
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In this work we have studied the relationship between the kinematics and shapes of Early Type Galaxies (ETGs) in rich clusters. In particular we were interested to extend the kinematic morphology density relation to the richest clusters. We obtained data from FLAMES/GIRAFFE to probe the stellar kinematics of a sample of 30 ETGs in the massive cluster Abell 1689 at z = 0.183, to classify them as Slow Rotators (SRs) or Fast Rotators (Frs). To date, this is the highest redshift cluster studied in this way. We simulated FLAMES/GIRAFFE observations of the local SAURON galaxies to account for the bias introduced compared to the ATLAS3D sample, which we used as a local comparison. We find that the luminosity function of SRs in Abell 1689 is the same as that in ATLAS3D, down to the faintest objects probed (MK ≈ -23). The number fraction of SRs over the ETG population in Abell 1689 is fSR = 0.15 +/- 0.03, consistent with the value found in the Virgo Cluster. However, within the cluster, fSR rises sharply with the projected number density of galaxies, rising from fSR = 0.01 in the least dense bin to fSR = 0.58 in the densest bin. We conclude that the fraction of SRs is not determined by the local number density of galaxies, but rather by the physical location within the cluster. This might be due to dynamical processes which cause SRs (on average more massive) to sink in the gravitational potential of the cluster. Next we explore the distribution of projected ellipticity ε in galaxies belonging to a sample of clusters from SDSS (z ε = 0.4 (a proxy for FRs) varies from cluster to cluster. We find some significant variations. We go on to probe the projected shape as a function of projected cluster-centric radius. In both samples we find that on average galaxies have progressively rounder projected shapes at lower cluster-centric projected distance. In the SDSS sample we show that this trend exists above and beyond the trend for brighter galaxies to be more common near the centre of clusters (bright galaxies are on average rounder). In order to disentangle the trend for SRs (which are rounder) to be more common near the centre of clusters, we isolate a subsample of FRs only, by considering only galaxies with ε > 0.4. We find that even the intrinsically flat FRs are on average rounder at lower projected cluster-centric distance. We conclude that the observed trend is due either to the dynamic heating of the stellar discs being strongest near the centre of clusters, or due to an anti-correlation of the bulge fractions with the cluster-centric distance.
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Buote, David Augustin. "The structure of elliptical galaxies and galaxy clusters." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/36556.
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Milvang-Jensen, Bo. "The evolution of spiral galaxies into distant clusters." Thesis, University of Nottingham, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275913.
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Spurgeon, Louise Elizabeth. "XMM and ROSAT observations of clusters of galaxies." Thesis, University of Leicester, 2003. http://hdl.handle.net/2381/30665.
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I present an investigation into the X-ray properties of galaxy clusters, consisting of a principal component analysis of ROSAT data and studies of three clusters observed with the XMM-Newton satellite. The principal component analysis provides an investigation into similarities between cluster surface brightness profiles. Initial results for 42 clusters are presented and compared to existing models. The cluster profiles are reproduced to good accuracy using three principal components. Correlation of the principal components to physical properties is investigated but the results are inconclusive. Observations of Abell 1413, Abell 665 and Abell 2163 made with XMM-Newton were investigated spectrally and spatially to determine cluster properties. Global temperatures were found to be 7.08 +/- 0.140.13 keV for Abell 665 and 11.98 +/- 1.2 keV for Abell 2163. The temperature and abundance profiles of the clusters are very different, with some differences attributed to the recent merging of subclusters in Abell 665 and Abell 2163. Spatial analysis of the cluster surface brightness profiles is undertaken with beta and NFW models. The profiles produced for the three clusters are used to estimate the variation of gas, gravitational and iron mass with radius. These are used to draw general conclusions, such supernovae numbers (NSNII 109--11). The cosmological density and matter density parameters are found; &OHgr;0 = 0.22 -- 0.33 +/- 0.1 and &OHgr; m ? 0.12+/-0.060.04. This suggests a low density universe, but is subject to uncertainty due to extrapolation to larger radii.
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Johnston, Evelyn Joanne. "The formation of lenticular galaxies in nearby clusters." Thesis, University of Nottingham, 2015. http://eprints.nottingham.ac.uk/14484/.
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Lenticular (S0) galaxies have long been thought of as evolved spirals, in which the star formation has been suppressed, the spiral arms have faded, and the luminosity of the bulge has been built up relative to the disc. However, the sequence of events that explains these three observations and leads to the formation of the final S0 galaxy is still uncertain. The progenitor spirals generally consist of bulges with old stellar populations surrounded by young, bright discs. Therefore, in order to explain the `quenching' of star formation in the disc and related increase in the bulge luminosity, an understanding of the individual star-formation histories of these two components is vital. In this thesis, we present a new technique to spectroscopically decompose the light from a galaxy into its bulge and disc components, from which the stellar populations and chemical compositions of the individual components can be extracted in order to determine the sequence of events leading to the transformation. Using spectroscopic bulge-disc decomposition, the spatial light profile in a two-dimensional galaxy spectrum can be separated wavelength-by-wavelength into bulge and disc components. This decomposition allows the construction of separate one-dimensional spectra representing purely the light from the bulge and disc, enabling studies of their individual star-formation histories with minimal contamination. This technique was applied to a sample of 30 S0s in the Virgo and Fornax Clusters, and analysis of the absorption line strengths within these spectra reveals that the bulges contain consistently younger and more metal-rich stellar populations than their surrounding discs. This result implies that the final episode of star formation before the progenitor spirals were fully quenched occurred in their central regions. Furthermore, the similarity in the alpha-element abundances of the bulges and discs indicates that the final episode of star formation in the bulge was fuelled using gas that has previously been chemically enriched in the disc. Together, these results present a picture in which the galaxy starts out as a typical spiral, with an old bulge surrounded by a young, star-forming disc. At some point in its life, gas is stripped from the galaxy, suppressing the star formation in the disc and causing the spiral arms to fade without inducing significant amounts of new star formation or disrupting the overall morphology of the galaxy. As the gas is removed, a fraction is also driven into the centre of the galaxy, where it fuels a final star-formation event in the bulge. This final episode of star formation consequently increases the luminosity of the bulge as the disc is already fading, and produces a central young, metal-rich stellar population. We have also shown that it is possible to spectroscopically decompose a galaxy using the different line-of-sight velocity distributions of kinematically distinct components. This technique was applied to NGC~4550, an unusual S0 galaxy in the Virgo Cluster with two counter-rotating stellar discs and a gaseous disc, to separate their individual stellar populations. Analysis of these stellar populations shows that the disc that co-rotates with the ionized gas is brighter and has a significantly younger mean age than the other disc, which are consistent with more recent star formation fuelled by the associated gaseous material. Therefore, the most likely formation mechanism for this galaxy is via an unusual gas accretion or merger scenario that built up a secondary stellar disc in a pre-existing S0 galaxy. The results presented in this thesis shed new light on the sequence of events that leads to the formation of S0 galaxies in cluster environments, and clearly demonstrates the importance of understanding the star-formation histories of the individual components within these galaxies in order to reconstruct the range of mechanisms by which they formed.
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Randriamampandry, Solohery Mampionona. "Stellar masses of star forming galaxies in clusters." University of the Western Cape, 2010. http://hdl.handle.net/11394/3028.
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Magister Scientiae - MScWe determine the stellar mass of star forming galaxies in the X-ray luminous cluster MS 0451.6-0305 at z ∼ 0.54. The stellar masses are estimated from fitting model spectral energy distributions (SEDs) to deep, optical UBRIz observations obtained from WIYN 3.5m telescope and public NIR K-band image from Palomar Observatory telescope. The model SEDs are based on the stellar population synthesis (SPS) model of Bruzual & Charlot (2003) and Conroy et al. (2009) that span a wide range of age, star formation history, Initial Mass Function (IMF), metallicity and dust content. We measure stellar masses for galaxies down to M∗∼2×10⁸M(.) We find a tight correlation between stellar masses derived from the two SPSs. We compare the derived stellar masses to the dynamical masses for a set of 25 star forming galaxies. The dynamical masses are derived from high resolution, spectroscopic observations of emission lines from the DEIMOS spectrograph on the Keck telescope. A strong correlation is seen between the dynamical and stellar mass for the galaxies; and the star forming galaxies show fairly constant ratio between stellar and dynamical mass. When comparing to the field sample of Guzm ́an et al. (2003) of luminous compact blue galaxies, we see an excess of low mass galaxies in the cluster.
South Africa
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Ziskin, Viktor. "Simulations of clusters of galaxies with thermal conduction." Available to US Hopkins community, 2003. http://wwwlib.umi.com/dissertations/dlnow/3080808.
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Yoshikawa, Koji. "Cosmological Hydrodynamic Simulations of Galaxies and Galaxy Clusters." 京都大学 (Kyoto University), 2002. http://hdl.handle.net/2433/149981.
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Cortese, Luca. "Environmental effects on galaxy evolution in nearby clusters." Aix-Marseille 1, 2005. http://www.theses.fr/2005AIX11018.
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Ce travail est dédié à l'étude des effets d'environnement sur l'évolution des galaxies, en utilisant un échantillon multi-longueur d'onde. En combinant pour la première fois des observations UV de GALEX à des données en optique, et en infrarouge j'ai déterminé l'histoire évolutive des galaxies. Touts les résultats obtenus montrent que : - les elliptiques géantes sont vieilles, à l'inverse des elliptiques naines qui contiennent toujours des populations stellaires jeunes. - L'importance relative des différents mécanismes d'environnement varie avec l'âge de l'univers. Les interactions de marée ont dominé dans l'univers passé mais la pression dynamique domine dans les amas d'aujourd'hui. - La classe des galaxies SO, n'est pas le résultat d'un seul mécanisme de transformation. - Il y a une forte corrélation entre l'âge moyen des populations stellaires et la masse des galaxies. Comprendre l'origine de cet effet représente aujourd'hui un des défis pour les modèles d'évolution des galaxies.
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Fang, Yuedong, Joseph Clampitt, Neal Dalal, Bhuvnesh Jain, Eduardo Rozo, John Moustakas, and Eli Rykoff. "Tidal stripping as a test of satellite quenching in redMaPPer clusters." OXFORD UNIV PRESS, 2016. http://hdl.handle.net/10150/622738.
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When darkmatter haloes are accreted by massive host clusters, strong gravitational tidal forces begin stripping mass from the accreted subhaloes. This stripping eventually removes all mass beyond a subhalo's tidal radius, with unbound mass remaining in the vicinity of the satellite for at most a dynamical time t(dyn). The N-body subhalo study of Chamberlain et al. verified this picture and pointed out a useful observational consequence: correlations between subhaloes beyond the tidal radius are sensitive to the infall time, t(infall), of the subhalo on to its host. We perform this correlation using similar to 160 000 red satellite galaxies in Sloan Digital Sky Survey redMaPPer clusters and find evidence that subhalo correlations do persist well beyond the tidal radius, suggesting that many of the observed satellites fell into their current host less than a dynamical time ago, t(infall) < t(dyn). Combined with estimated dynamical times t(dyn) similar to 3-5 Gyr and SED fitting results for the time at which satellites stopped forming stars, t(quench) similar to 6 Gyr, we infer that for a significant fraction of the satellites, star formation quenched before those satellites entered their current hosts. The result holds for red satellites over a large range of cluster-centric distances 0.1-0.6 Mpc h(-1). We discuss the implications of this result formodels of galaxy formation.
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Masters, Craig Eugene Ashman Keith M. "The formation of low metallicity globular clusters." Diss., UMK access, 2007.
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Thesis (Ph. D.)--Dept. of Physics and Dept. of Mathematics. University of Missouri--Kansas City, 2007."A dissertation in physics and mathematics." Advisor: Keith M. Ashman. Typescript. Vita. Title from "catalog record" of the print edition Description based on contents viewed Nov. 13, 2007. Includes bibliographical references (leaves 67-70). Online version of the print edition.
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Kindl, Enrico. "A photometric and morphological study of compact groups of galaxies and their environments." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/30722.
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This thesis examines properties of galaxies in and around compact groups. Astrometry, photometry and morphological classifications are derived from CCD images for all 463 galaxies in Hickson's sample of 100 compact groups. Some minor revisions to the membership of the original catalog are made. At high galactic latitude (b > 30°), the catalog is estimated to be 90% complete for groups with total B[formula omitted] magnitude 13.0 or less. 49% of all the catalogued galaxies, and 48% of first-ranked galaxies are spiral. No significant difference is found between the distribution of morphological types of first-ranked galaxies and all group galaxies. Morphological concordance occurs among galaxies within a group: more galaxies are the same type (spiral or nonspiral), than would be expected by chance. Galaxy morphological type correlates with group optical luminosity and, more strongly, with velocity dispersion, but not with galaxy space density. These results imply that the morphological types of galaxies in compact groups are strongly influenced by the environment, and that this influence occurs mostly at the time of galaxy formation.
Fields surrounding 97 compact groups with known redshifts were examined on the Palomar Observatory Sky Survey prints. 3889 galaxies were identified within 1.125h⁻¹ Mpc of the centre of each group. Coordinates, magnitudes, diameters, and Hubble types are derived for these galaxies. 78% of the groups show no significant excess of field galaxies within 0.5h⁻¹ Mpc. This indicates that most compact groups are truly isolated. 59% of these field galaxies were classified as spiral, a higher fraction that for the group galaxies. This difference is more pronounced for groups which do show a significant field galaxy excess. These results indicate that most
groups are dense dynamical entities.
Monte-Carlo calculations indicate that 35% of galaxy quintets are predicted to contain a single discordant redshift due to the chance alignment of an unrelated field galaxy. This is in agreement with the observed number of four discordant quintets in 10. These results are consistent with the cosmological interpretation of galaxy redshifts.Science, Faculty of
Physics and Astronomy, Department of
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De, Propris Roberto. "The faint end of the luminosity function in clusters of galaxies." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1996. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq21930.pdf.
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