A Comparison of the Effects of Local and Global Environment on Galaxy Evolution in Low Redshift Galaxy Clusters PDF Download

Author: Brittany Howard
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Category :
Languages : en
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Author: Anna Delahaye
Publisher:
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Category :
Languages : en
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"Galaxy properties such as colour, star-formation rate, and morphology are influenced by the environments in which they reside. In particular, the environments of galaxy clusters have been shown be very efficient at quenching star-formation and altering other observed galactic properties, although the specific mechanisms responsible for this evolution are not fully understood. Additionally, the effect that the cluster environment has on galaxies does not appear to be consistent at all redshifts, with high-redshift cluster galaxies having different observed properties compared to their local counterparts. In this thesis, two studies are presented that investigate the role of high-redshift galaxy cluster environments on their galactic populations.The first study is an extensive photometric survey of the supercluster RCS2319+00, a massive supercluster system comprising three virialized cluster cores in close proximity with one another in projected space as well as redshift space. The system is located at a redshift of z = 0.9 and is expected to merge into a single 10^15 solar mass cluster by z = 0.5, and is therefore a progenitor of the most massive cluster systems we see in the nearby universe today. Spectroscopic and submillimetre surveys have previously uncovered a complicated system of filamentary structure and infalling groups. To complement the previous studies, we assemble a large multiwavelength catalogue to identify cluster members based on photometric properties.With a photometric catalogue complete with photometric redshifts for over 16,000 objects across the central RCS2319 field, we compile a cluster catalogue of nearly 1,800 cluster members. Using proxies for both local and global environments, we investigate the mass and colour properties of cluster galaxies depending on their specific environments within the supercluster. While we do not find a strong dependence on global environment, we do recover both a mass-density and colour-density relation depending on the local overdensity suggesting that immediate surroundings influence galactic properties more strongly than the overall structure in which it resides.The second study presented investigates the presence of merging systems in high-redshift cluster environments compared to the field. We use a sample of four galaxy clusters (1.59

Author: Lu Shen
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ISBN: 9781392737200
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Languages : en
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This dissertation describes research performed in the field of observational astrophysics as part of the Observations of Redshift Evolution in Large Scale Environment (ORELSE) survey, an ongoing multi-wavelength imaging and spectroscopic campaign investigating galaxyevolution in the environments of large scale structures (LSSs) surrounding 16 known clusters at the redshift range of $0.6 [less than or equal to] z [less than or equal to] 1.3. The aim of this dissertation is to contextualize how environment influences galaxy evolution among radio-emitting galaxies and radio Active Galactic Nucleus (RAGN) in a wide dynamic range of environments over cosmic time. In each of the three main chapters I present a sample of radio galaxies and an analysis of the connection to their environments. In the first part of this dissertation I describe the context of radio galaxies, galaxy environments, and the current state of the ORELSE survey. This initial section will set the framework for the variety of studies presented in this thesis. In the second part of this dissertation I present three studies undertaken to investigate various aspects of radio galaxies and the role of there environments. The first of these studies is an investigation of radio galaxies that are cross-matched to spectroscopically-confirmed galaxies in the large scale structures in the five fields of the ORELSE survey. To appropriately classify radio galaxies and study the properties of them separately, a two stage classification method is designed, where radio galaxies are classified into three sub-classes: active galactic nucleus (AGN), Hybrid, and star-forming galaxy (SFG). AGN tend to be preferentially located in locally dense environments and in the cores of clusters/groups, while SFGs exhibit a strong preference for intermediate-density global environments, with these preferences persisting when comparing to galaxies of similar color and stellar mass. These result has important consequences for galaxy evolutionary scenarios, as these two types of galaxies are thought to be the beginning and the end of galaxy evolution. The second of these studies is an investigation of the quenching effect of radio AGN (RAGN) on their neighboring galaxies. In this study, an elevated fraction of quenched RAGN neighbors was found in the most dense local and cluster environments, compared to those of non-RAGN control samples matched to the RAGN population in colour, stellar mass, and local environment. This result suggests that RAGN residing within clusters might heat the intracluster medium (ICM) affecting both in situ star formation and any inflowing gas that remains in their neighbors. This work has important consequences for understanding AGN feedback out of their host galaxies, which is the subject of much debate among astronomers.The final study in this dissertation is a full investigation of the co-evolution of AGN and star formation in radio galaxies in eight ORELSE fields. This study was first motivated by the Hybrid population analyzed in the first study, whose properties suggested that they have coeval star-formation and AGN activity with high accretion efficiency. Combining radio with mid-infrared and far-infrared data available in the ORELSE survey, the AGN and star formation contributions to the total infrared luminosity are well constrained. I present evidence for AGN quenching of the star formation in a rapid timescale in an orbital motion around the clusters/groups. This result has important consequences for galaxy evolutionary scenarios by connecting the two processes that are difficult to separate observationally and are thought to be related.

Author: Ryan Leaman
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Languages : en
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This thesis presents observations and analysis relating to the understanding of processes that govern the formation and evolution of low mass galactic systems. In particular we have focused on separating out the contribution to the chemical and dynamical evolution of dwarf galaxies due to solely secular (internal) processes compared to external effects from the local environment a galaxy resides in. Our observational data focus on an extremely isolated dwarf galaxy, WLM, which we demonstrate has had a uniquely quiescent tidal history, thereby making it an excellent test case for such a study. With spectroscopic and photometric observations of the resolved stars and neutral gas in WLM we have been able to characterize the chemical, structural and kinematic properties of this gas rich dwarf galaxy. As WLM has not been subject to strong tidal or ram-pressure stripping of its stellar and gaseous populations, we have been able to compare the dynamical evolution and chemical history of WLM to theoretical models which are environment independent. A differential comparison of WLM to more environmentally processed dwarf galaxies in the Local Group has revealed that WLM's structural and dynamical state is far from the idealized picture of dIrrs as thin gas-rich rotating systems. The stellar component of WLM shows equal parts rotation and dispersion, and both the gaseous and stellar structural properties show an intrinsically thick axisymmetric configuration. The time evolution of the random (dispersion) component of the stellar orbital energy shows an increase with stellar age, which we show is consistent with secular processes alone - such as disk heating from giant molecular clouds and dark matter substructure. While the degree to which the thick structural and dynamically hot configuration for WLM is surprising, its chemical properties show remarkably consistent values with other galaxies of the same halo mass. Comparing the spatial chemical trends in WLM with other dwarf galaxies we identify a correlation between the strength of the radial abundance gradients and the angular momentum content of dwarf galaxies in the Local Group. Finally using a large sample of chemical abundance measurements in the literature for dwarf galaxies and star clusters, we demonstrate that their distributions of chemical elements all exhibit a binomial form, and use the statistical properties of the distributions to identify a new metric for differentiating low luminosity stellar systems. We further apply a simple binomial chemical evolution model to describe the self-enrichment and pre-enrichment in the two classes of objects, and suggest how this may be used to place constraints on the formation environments of globular clusters in particular.

Author: Manuel Duarte
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Galaxies lie in a large panel of environments from isolated galaxies, to pairs, groups or clusters. The environment is expected to have an impact on galaxy properties such as morphology, stellar formation, metallicity\ldots. Some studies already tried to quantify the importance of the global environment (linked to the dark matter halo mass) and the local environment (galaxy position in the group). These studies have shown that the environment plays a minor role except for low mass galaxies. But the quantification of the environment is difficult since detected groups in redshift space (the only one accessible by the observer) are very elongated, making it difficult to extract spherical groups in real space. If these quantification errors are too important, environment effects will not be measured correctly. Moreover, other physical processes are at work inside groups whose relative roles are not well understood. For example, major or minor mergers (rich or poor in gas, between satellite galaxies, or after the decay of the orbit of a satellite onto the central galaxy by dynamical friction), rapid flybys harassing galaxies, stripping of the interstellar gas by ram pressure or of the gaseous reservoir by tidal forces. Although semi-analytical codes of galaxy formation from initial conditions of a LambdaCDM Universe fit well a large set of observed relations, there are still some discrepancies that might be possibly explained by a lack of correct physical recipes of environmental effects in these models. Our goal with this thesis is to have a detailed comprehension of the role of environment on galaxy properties, and finally determine the major physical processes in the modulation of these properties with both local and global environment. For this, an optimal extraction of galaxy groups from the projected phase space is necessary. We performed a study and re-implementation of some existing group finder to estimate their strengths and weaknesses in the detection of galaxy groups. A galaxy mock catalogue in redshift space, designed to mimic the primary spectroscopic sample of the SDSS survey was created to apply several galaxy group algorithms. An advantage is the already known membership that we can compare to galaxy groups extracted from redshift space. Semi-analytical codes of galaxy formation give us such galaxy catalogs we transformed to be coherent with the vision of an observer. With these mock catalogues, we tested the very popular Friends-of-Friends grouping algorithm. We determined the optimal linking lengths against the set of tests and optimal criterion we developed to judge the efficiency of an algorithm. It appears that this choice of linking lengths depends on the scientific goal to do with the group catalogue. A large part of the thesis consisted on the realization of a new grouping algorithm called MAGGIE (Models and Algorithm for Galaxy Groups, Interlopers and Environment), Bayesian and probabilistic. MAGGIE uses our priors acquired with analysis of cosmological simulations for large scale structure and of observations obtained from large galaxy surveys, to better constrain the selection of galaxy groups from redshift space. Comparison of MAGGIE with the FoF algorithm shows that MAGGIE is superior in avoiding the fragmentation of real space groups, the membership selection (completeness, reliability) and in the group properties (group mass, luminosity). The better performance of MAGGIE comes from its probabilistic nature, the use of astrophysical and cosmological priors, and the use of halo abundance matching technique linking central galaxy distributions (stellar mass or luminosity) to physical properties of dark matter halos. The future application of MAGGIE on galaxy surveys such as the Sloan Digital Sky Survey or the deeper Galaxy and Mass Assembly, taking care of their own observational problems, should improve our understanding of the modulation of galaxy properties with their global and local environments and physical processes operating inside galaxy groups.

Author:
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Category : Aeronautics
Languages : en
Pages : 506

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Author: Catarina Lobo
Publisher: Springer Science & Business Media
ISBN: 9401001073
Category : Science
Languages : en
Pages : 256

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Galaxy groups and clusters provide excellent laboratories for studying galaxy properties in different environments and at different look-back times. In particular, the recent detections of high-redshift cluster candidates, only possible with the current high-technology instrumentation, add a new dimension to the problem. Along with the ever increasing computing power and sophisticated algorithms to model clusters of galaxies, it may help us to understand the origins of today's groups and clusters, as well as of their member galaxies. These workshop proceedings provide a snapshot of the current research in this subject, covering the observations, theory and numerical simulations relevant to galaxy evolution in groups and clusters. In this book, intended primarily to researchers in the field, particular emphasis is given to the recent impressive progress in the field, on important new results, and on the future prospects and open questions to be tackled.

Author: Emil S Noordeh
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Languages : en
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The nature of galaxy evolution from the early Universe to the present day is intricately linked to large-scale environment: the environments of galaxies are expected to play a critical role in the development of their morphologies, star formation activity, and the activity of their central Super Massive Black Holes (SMBHs). Large scale environment can strongly and rapidly affect gas reservoirs which are a prerequisite for both star formation and SMBH activity. We would expect the effect of environment to be most pronounced in massive galaxy clusters, where both the density of the intracluster medium and number density of galaxies are the highest. This has indeed been established for star formation activity in the local and intermediate redshift universe, where dense, cluster environments are more likely to host elliptical, quiescent galaxies. However, the impact of the cluster environment on SMBH activity has been significantly less clear. At high redshift, the impact of clusters on galaxy activity is even less well understood. This is due to both a decline in the number of massive clusters at high redshift as well as increasing observational difficulty in reliably identifying and characterizing both the clusters themselves and their member galaxies. This dissertation tries to bring some clarity to these unknowns. First, we present an analysis of SMBH activity in a sample of massive clusters at intermediate redshift where we confirm a dependence of this activity on cluster mass. Second, we describe the spectroscopic characterization of one of the highest redshift galaxy clusters ever discovered, existing at a lookback time of more than 10 billion years. We model the stellar population of its member galaxies and trace their formation back to the cosmic dark ages, when the Universe was only 370 million years old. Finally, we do a deep dive into this cluster's galaxy population and find it to be remarkably similar to that of clusters in the local universe. We identify a tremendously enhanced quiescent fraction relative to the field and find evidence for accelerated size-evolution in these quiescent galaxies.

Author: Manuel Duarte
Publisher:
ISBN:
Category :
Languages : en
Pages : 129

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Book Description
Galaxies lie in a large panel of environments from isolated galaxies, to pairs, groups or clusters. The environment is expected to have an impact on galaxy properties such as morphology, stellar formation, metallicity\ldots. Some studies already tried to quantify the importance of the global environment (linked to the dark matter halo mass) and the local environment (galaxy position in the group). These studies have shown that the environment plays a minor role except for low mass galaxies. But the quantification of the environment is difficult since detected groups in redshift space (the only one accessible by the observer) are very elongated, making it difficult to extract spherical groups in real space. If these quantification errors are too important, environment effects will not be measured correctly. Moreover, other physical processes are at work inside groups whose relative roles are not well understood. For example, major or minor mergers (rich or poor in gas, between satellite galaxies, or after the decay of the orbit of a satellite onto the central galaxy by dynamical friction), rapid flybys harassing galaxies, stripping of the interstellar gas by ram pressure or of the gaseous reservoir by tidal forces. Although semi-analytical codes of galaxy formation from initial conditions of a LambdaCDM Universe fit well a large set of observed relations, there are still some discrepancies that might be possibly explained by a lack of correct physical recipes of environmental effects in these models. Our goal with this thesis is to have a detailed comprehension of the role of environment on galaxy properties, and finally determine the major physical processes in the modulation of these properties with both local and global environment. For this, an optimal extraction of galaxy groups from the projected phase space is necessary. We performed a study and re-implementation of some existing group finder to estimate their strengths and weaknesses in the detection of galaxy groups. A galaxy mock catalogue in redshift space, designed to mimic the primary spectroscopic sample of the SDSS survey was created to apply several galaxy group algorithms. An advantage is the already known membership that we can compare to galaxy groups extracted from redshift space. Semi-analytical codes of galaxy formation give us such galaxy catalogs we transformed to be coherent with the vision of an observer. With these mock catalogues, we tested the very popular Friends-of-Friends grouping algorithm. We determined the optimal linking lengths against the set of tests and optimal criterion we developed to judge the efficiency of an algorithm. It appears that this choice of linking lengths depends on the scientific goal to do with the group catalogue. A large part of the thesis consisted on the realization of a new grouping algorithm called MAGGIE (Models and Algorithm for Galaxy Groups, Interlopers and Environment), Bayesian and probabilistic. MAGGIE uses our priors acquired with analysis of cosmological simulations for large scale structure and of observations obtained from large galaxy surveys, to better constrain the selection of galaxy groups from redshift space. Comparison of MAGGIE with the FoF algorithm shows that MAGGIE is superior in avoiding the fragmentation of real space groups, the membership selection (completeness, reliability) and in the group properties (group mass, luminosity). The better performance of MAGGIE comes from its probabilistic nature, the use of astrophysical and cosmological priors, and the use of halo abundance matching technique linking central galaxy distributions (stellar mass or luminosity) to physical properties of dark matter halos. The future application of MAGGIE on galaxy surveys such as the Sloan Digital Sky Survey or the deeper Galaxy and Mass Assembly, taking care of their own observational problems, should improve our understanding of the modulation of galaxy properties with their global and local environments and physical processes operating inside galaxy groups.

Author: Eric D. Feigelson
Publisher: Cambridge University Press
ISBN: 052176727X
Category : Science
Languages : en
Pages : 495

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Modern Statistical Methods for Astronomy: With R Applications.