Galaxy Groups From Observations And Simulations
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Galaxy Groups From Observations And Simulations
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Author :
language : en
Publisher:
Release Date :
Galaxy Groups From Observations And Simulations written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on with categories.
The cold dark matter model has become the leading theoretical paradigm for the formation of structure in the Universe. Together with the theory of cosmic inflation, this model makes a clear prediction for the initial conditions for structure formation and predicts that structures grow hierarchically through gravitational instability. As a result, small structures collapse first and eventually build large structures such as groups and cluster of galaxies. While clusters are among the most massive bound structures in the Universe, groups are more numerous and most of the galaxies reside within galaxy groups. Testing this model requires that the precise measurements delivered by galaxy surveys can be compared to robust and equally precise theoretical models. The current project consists of two parts. In the first part, we investigate the existence and evolution of early-formed fossil galaxy groups, and the development of the luminosity gap between its brightest galaxies. We study the correlation of these properties with the group mass assembly history, by comparing observations to the Millennium simulation of dark matter particles, and the associated semi-analytic catalogues of galaxies, together with the Millennium gas simulation. Fossil Galaxy Groups are believed to be the end result of galaxies merging within a normal galaxy group, leaving behind the X-ray halo characteristic of a group. The sample of fossils in our study are selected according to the useful definition of fossil groups. The luminosity gap statistics in the Millennium Run are compared to the theoretical models. The study of the mass evolution of fossils shows that in comparison to normal groups, fossils are more evolved systems and have assembled their masses at higher redshifts, while normal groups are still evolving. Our work suggests the earlier formation and higher mass concentration of fossil systems. The estimated space densities from the Millennium Run are smaller (sometimes in agreement withi.
Galaxy Groups From Observations And Simulations
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Author : Aliakbar Dariush
language : en
Publisher:
Release Date : 2008
Galaxy Groups From Observations And Simulations written by Aliakbar Dariush and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008 with categories.
The Dynamic Evolution Of Galaxy Clusters
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Author : Robert C. Berrington
language : en
Publisher:
Release Date : 2000
The Dynamic Evolution Of Galaxy Clusters written by Robert C. Berrington and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2000 with categories.
Galaxy Evolution In Groups And Clusters
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Author : Catarina Lobo
language : en
Publisher: Springer Science & Business Media
Release Date : 2012-12-06
Galaxy Evolution In Groups And Clusters written by Catarina Lobo and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-12-06 with Science categories.
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.
New Insights Into Galaxy Clusters From Simulations To Observations
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Author : Universitat de València. Facultat de Física
language : en
Publisher:
Release Date : 2011
New Insights Into Galaxy Clusters From Simulations To Observations written by Universitat de València. Facultat de Física and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with categories.
Groups Of Galaxies
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Author : Pekka Heinämäki
language : en
Publisher:
Release Date : 1998
Groups Of Galaxies written by Pekka Heinämäki and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1998 with Black holes (Astronomy) categories.
Exploring The Nature Of Fossil Galaxy Systems With Simulations And X Ray Observations
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Author : Alisha Kundert
language : en
Publisher:
Release Date : 2018
Exploring The Nature Of Fossil Galaxy Systems With Simulations And X Ray Observations written by Alisha Kundert and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018 with categories.
Fossil galaxy groups and clusters are characterized by an extreme difference in brightness between their central and satellite galaxies. This magnitude gap has been proposed to form as the result of significant mergers of massive satellite galaxies with the central galaxy over time which suggests fossils represent an interesting stage of galaxy system evolution and hierarchical structure formation. The objective of this thesis is to use X-ray observations and simulations to constrain the properties of fossil galaxy systems with the goal of understanding their nature and origin. In this thesis, the properties of fossil systems are first examined by constructing the global optical and X-ray scaling relations of fossils across the group and cluster mass regimes. Then, using the Illustris cosmological simulation, the mass assembly histories of fossil central galaxies and their group halos are traced directly. Lastly, the X-ray properties of fossil system RX J1159.8+5531 are investigated in detail through radial profiles of intracluster medium temperature and density, which are used to determine the total mass profile and mass concentration parameter of this group. These studies point towards fossil systems as a temporary relaxed state in the evolution of galaxy groups and clusters.
The Structure And Environment Of Galaxy Clusters In Simulations And Observations
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Author : Matthew Fong
language : en
Publisher:
Release Date : 2019
The Structure And Environment Of Galaxy Clusters In Simulations And Observations written by Matthew Fong and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019 with Cosmology categories.
Galaxy clusters are powerful testing grounds for cosmology. They are the largest, most massively bound objects in the Universe and can give us deep insights on how baryons, dark matter, and dark energy impacts on the formation of large scale structure in the cosmos. In this dissertation we study the structure and environment of clusters, how neutrinos impact on cluster masses, and how we may find them. We study cluster profiles on large scales to gain better understanding on the relationship between cosmic web filaments and clusters that reside in the nodes, which gives insight on the evolution of clusters from their environment. For more than two decades, the Navarro, Frenk, and White (NFW) model has stood the test of time; it is used to describe the distribution of mass in galaxy clusters out to their outskirts, beyond which the NFW model is no longer applicable. In this dissertation we assess how well the parameterised Diemer & Kravstov (DK) mass density profile describes the mass distribution of galaxy clusters extracted from cosmological simulations. This is determined from averaged synthetic lensing measurements of the 50 most massive clusters extracted from the OverWhelmingly Large Simulations (Cosmo-OWLS). The characteristics of the data reflect the Weighing the Giants survey and data from the future Large Synoptic Survey Telescope (LSST). In comparison with the NFW model, the DK model is favored by the averaged data, in particular for the LSST data, where the number density of background galaxies is higher. The DK profile depends on the accretion history of clusters which is specified in the current study. Eventually subsamples of galaxy clusters with qualities indicative of disparate accretion histories could be studied. We also study the impact of baryonic processes and massive neutrinos on weak lensing (WL) peak statistics that can be used to constrain cosmological parameters. We use the BAHAMAS suite of cosmological simulations, which self-consistently include baryonic processes and the e↵ect of massive neutrino free-streaming on the evolution of structure formation. We construct synthetic WL catalogues by ray-tracing through light-cones, and use the aperture mass statistic for the analysis. The WL peaks reflect the cumulative signal from massive bound objects and general large-scale structure. We present the first study of WL peaks in simulations that include both baryonic physics and massive neutrinos, so that the uncertainty due to physics beyond the gravity of dark matter can be factored into constraints on cosmological models. Assuming a fiducial model of baryonic physics, we also investigate the correlation between peaks and massive haloes, over a range of neutrino masses. As higher neutrino mass tends to suppress the formation of massive structures in the Universe, the halo mass function and lensing peak counts are therefore modified as a function of neutrino mass. Over most of the S/N .5, the impact of fiducial baryonic physics is greater (less) than neutrinos for 0.06 and 0.12 (0.24 and 0.48) eV models. Both baryonic physics and massive neutrinos should be accounted for when deriving cosmological parameters from weak lensing observations.
Observations And Modeling Of Merging Galaxy Clusters
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Author : Nathan Ryan Golovich
language : en
Publisher:
Release Date : 2017
Observations And Modeling Of Merging Galaxy Clusters written by Nathan Ryan Golovich and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with categories.
Context: Galaxy clusters grow hierarchically with continuous accretion bookended by major merging events that release immense gravitational potential energy (as much as ~1065 erg). This energy creates an environment for rich astrophysics. Precise measurements of the dark matter halo, intra-cluster medium, and galaxy population have resulted in a number of important results including dark matter constraints and explanations of the generation of cosmic rays. However, since the timescale of major mergers (~several Gyr) relegates observations of individual systems to mere snapshots, these results are difficult to understand under a consistent dynamical framework. While computationally expensive simulations are vital in this regard, the vastness of parameter space has necessitated simulations of idealized mergers that are unlikely to capture the full richness. Merger speeds, geometries, and timescales each have a profound consequential effect, but even these simple dynamical properties of the mergers are often poorly understood. A method to identify and constrain the best systems for probing the rich astrophysics of merging clusters is needed. Such a method could then be utilized to prioritize observational follow up and best inform proper exploration of dynamical phase space. Task: In order to identify and model a large number of systems, in this dissertation, we compile an ensemble of major mergers each containing radio relics. We then complete a pan-chromatic study of these 29 systems including wide field optical photometry, targeted optical spectroscopy of member galaxies, radio, and X-ray observations. We use the optical observations to model the galaxy substructure and estimate line of sight motion. In conjunction with the radio and X-ray data, these substructure models helped elucidate the most likely merger scenario for each system and further constrain the dynamical properties of each system. We demonstrate the power of this technique through detailed analyses of two individual merging clusters. Each are largely bimodal mergers occurring in the plane of the sky. We build on the dynamical analyses of Dawson (2013b) and Ng et al. (2015) in order to constrain the merger speeds, timescales, and geometry for these two systems, which are among a gold sample earmarked for further follow up. Findings: MACS J1149.5+2223 has a previously unidentified southern subcluster involved in a major merger with the well-studied northern subcluster. We confirm the system to be among the most massive clusters known, and we study the dynamics of the merger. MACS J1149.5+2223 appears to be a more evolved system than the Bullet Cluster observed near apocenter. ZwCl 0008.8+5215 is a less massive but a bimodal system with two radio relics and a cool-core "bullet'' analogous to the namesake of the Bullet Cluster. These two systems occupy different regions of merger phase space with the pericentric relative velocities of ~2800 km s−1 and ~1800 km s−1 for MACS J1149.5+2223 and ZwCl 0008.8+5215, respectively. The time since pericenter for the observed states are ~1.2 Gyr and ~0.8 Gyr, respectively. In the ensemble analysis, we confirm that radio relic selection is an efficient trigger for the identification of major mergers. In particular, 28 of the 29 systems exhibit galaxy substructure aligned with the radio relics and the disturbed intra-cluster medium. Radio relics are typically aligned within 20° of the axis connecting the two galaxy subclusters. Furthermore, when radio relics are aligned with substructure, the line of sight velocity difference between the two subclusters is small compared with the infall velocity. This strongly implies radio relic selection is an efficient selector of systems merging in the plane of the sky. While many of the systems are complex with several simultaneous merging subclusters, these systems generally only contain one radio relic. Systems with double radio relics uniformly suggest major mergers with two dominant substructures well aligned between the radio relics. Conclusions: Radio relics are efficient triggers for identifying major mergers occurring within the plane of the sky. This is ideal for observing offsets between galaxies and dark matter distributions as well as cluster shocks. Double radio relic systems, in particular, have the simplest geometries, which allow for accurate dynamical models and inferred astrophysics. Comparing and contrasting the dynamical models of MACS J1149.5+2223 and ZwCl 0008.8+5215 with similar studies in the literature (Dawsonm 2013b; Ng et al., 2015; vam Weeren et al., 2017), a wide range of dynamical phase space ~1500-3000 km s−1 at pericenter and ~500-1500 Myr after pericenter) may be sampled with radio relic mergers. With sufficient samples of bimodal systems, velocity dependence of underlying astrophysics may be uncovered. Perspectives: With the gold sample identified from our ensemble analysis, our photometric observations will be used to constrain the dark matter distribution with gravitational lensing (in studies analogous to Jee et al., 2015, 2016). Furthermore, as new radio surveys identify additional radio relic systems, more may be added to this gold sample. These systems are best served to test self-interacting dark matter hypotheses, but observational based models much be complimented with detailed simulations, and in order to move forward with this work, more realistic initial conditions based on observations must be utilized. Collaborators and I are actively studying existing cosmological N-body simulations in search of analogs to these systems, which may then be re-simulated at higher resolution with new physics included.
New Insights Intro Galaxy Clusters
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Author : Susana Planelles Mira
language : en
Publisher:
Release Date : 2012
New Insights Intro Galaxy Clusters written by Susana Planelles Mira and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with categories.