Download or read book Internal Dynamics of Galaxy Clusters in the Red Sequence Cluster Survey written by Kris Blindert and published by . This book was released on 2006 with total page 250 pages. Available in PDF, EPUB and Kindle. Book excerpt: We compute the global dynamical properties of the clusters in our survey, such as velocity dispersion and mass, and use them to explore the properties of RCS clusters as functions of total cluster mass. In particular, we first examine the optical richness as an inexpensive proxy for mass. The calibration of this relation is an important ingredient in the construction of the cluster mass function, which is used to constrain cosmological parameters. Our relation and scatter are consistent with self-calibrated cosmological parameter results. We also study the cluster mass-to-light ratios, and how they scale with mass. We compare our results to other observations and to structure formation models. Although the scatter in this relation is large, we find agreement among remarkably different types of galaxy clusters and groups; however, current structure formation models do not accurately reproduce the variation of M/L with mass. We present a spectroscopic survey of clusters of galaxies, designed to explore the distribution of matter, and its relation to light, in these massive systems. Our sample is drawn from the Red-sequence Cluster Survey (RCS), and is composed of 33 clusters with a wide range of optical richness and a moderate range of redshift. We obtained spectra of 56 to 529 objects per cluster, which yielded over 3500 redshifts of which 1014 are cluster members. To account for survey incompleteness due to sparse sampling, we constructed several empirical corrections so that our redshift catalogue is suitable for use in dynamical analysis. To boost statistics and allow us to perform a more detailed dynamical analysis of clusters, we stack our data into "ensemble" clusters. Cosmological simulations predict a roughly universal density profile for dark matter haloes over many scales, and a relation between halo mass and the concentration of the profile. We analyse the ensembles using the jeans equations, and recover density profiles for several ensemble clusters of different masses. Although the sampling of our data at small radii is insufficient to constrain some quantities of interest such as the inner core slope of the density profile, we can constrain the concentrations and orbital anisotropies for the ensemble clusters. We find they agree with predictions and previous observations: namely, that galaxies in clusters follow roughly isotropic orbits, and the concentrations of cluster density profiles are consistent with the prediction one would obtain from their masses. We also estimate the variation of concentration with redshift, finding a slightly stronger evolution than expected.

Download or read book Outskirts of Galaxy Clusters IAU C195 written by International Astronomical Union. Colloquium and published by Cambridge University Press. This book was released on 2004-12-16 with total page 586 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book contains the proceedings of the International Astronomical Union Colloquium no. 195, held in Torino, Italy in 2004. The meeting investigated the formation of galaxies within a full cosmological context, focusing on the outer regions of galaxy clusters. The observed correlation of optical and radio properties of galaxies with their environment indicates that the formation and evolution of galaxies is intimately linked to the formation of large scale structure. With chapters written by leading authorities in the field, this timely volume investigates the role of the environment in determining the properties of galaxies. It describes the distribution of matter and galaxies on the largest scales in the Universe, the processes of cluster and galaxy formation, their role and interplay. This is a valuable collection of review articles for professional astronomers.

Download or read book Merging Processes in Galaxy Clusters written by L. Feretti and published by Springer Science & Business Media. This book was released on 2006-04-18 with total page 329 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mergers are the mechanisms by which galaxy clusters are assembled through the hierarchical growth of smaller clusters and groups. Major cluster mergers are the most energetic events in the Universe since the Big Bang. Many of the observed properties of clusters depend on the physics of the merging process. These include substructure, shock, intra cluster plasma temperature and entropy structure, mixing of heavy elements within the intra cluster medium, acceleration of high-energy particles, formation of radio halos and the effects on the galaxy radio emission. This book reviews our current understanding of cluster merging from an observational and theoretical perspective, and is appropriate for both graduate students and researchers in the field.

Download or read book Looking Wider and Further written by and published by . This book was released on 2016 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: Galaxy clusters are rare objects in the universe, but on-going wide field optical surveys are identifying many thousands of them to redshift 1.0 and beyond. Using early data from the Dark Energy Survey (DES) and publicly released data from the Sloan Digital Sky Survey (SDSS), this dissertation explores the evolution of cluster galaxies in the redshift range from 0 to 1.0. As it is common for deep wide field sky surveys like DES to struggle with galaxy detection efficiency at cluster core, the first component of this dissertation describes an efficient package that helps resolving the issue. The second part focuses on the formation of cluster galaxies. The study quantifies the growth of cluster bright central galaxies (BCGs), and argues for the importance of merging and intra-cluster light production during BCG evolution. An analysis of cluster red sequence galaxy luminosity function is also performed, demonstrating that the abundance of these galaxies is mildly dependent on cluster mass and redshift. The last component of the dissertation characterizes the properties of galaxy filaments to help understanding cluster environments.

Download or read book Dusty Star forming Galaxies Within High redshift Galaxy Clusters written by Allison Noble and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "We present a multi-wavelength perspective of star-forming galaxies within high-redshift galaxy clusters. The clusters derive from the Red-sequence Cluster Survey (RCS) and the Spitzer Adaptation of the Red-sequence Cluster Survey (SpARCS), and possess ample spectroscopic coverage, yielding numerous confirmed cluster members. This thesis consists of a collection of distinct but related works, focusing on environmental effects within the dense regions of clusters---some of the rarest structures in the Universe. We exploit the high sensitivities of cutting-edge infrared and submillimeter telescopes to glean the wealth of information encoded within the thermal portion of the spectral energy distribution, including infrared luminosities and dust temperatures. This allows us to uncover various trends within the star-forming population as a function of environment. Moreover, we develop a novel definition of environment, based on the phase space of radius and velocity, to account for the various accretion histories of galaxies onto clusters; it thereby probes the time-averaged density that each galaxy population has experienced. Using this tracer of environment, we find a significant depression in the star formation rate per unit stellar mass for star-forming galaxies within cluster cores at z~0.9 and z~1.2, in contrast to the flat trend that results from conventional definitions of environment. We also discover a population of galaxies that have lower dust temperatures compared to both infalling galaxies and those that were accreted at the earliest stages of the formation of the cluster. Taken together, these trends in star formation rate and dust temperature can help elucidate which, if any, quenching mechanisms are active within cluster environments. Finally, we report the serendipitous detection of an overdensity of submillimeter-bright galaxies located behind a merging z~0.9 supercluster, which could signify a highly star-forming protocluster at z~3." --

Download or read book Submillimeter Imaging of High redshift Galaxy Clusters written by Allison G. Noble and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Precision Cosmology with Galaxy Cluster Surveys written by Hao-Yi Wu and published by Stanford University. This book was released on 2011 with total page 234 pages. Available in PDF, EPUB and Kindle. Book excerpt: The acceleration of the universe, which is often attributed to "dark energy, " has posed one of the main challenges to fundamental physics. Galaxy clusters provide one of the most sensitive probes of dark energy because their abundance reflects the growth rate of large-scale structure and the expansion rate of the universe. Several large galaxy cluster surveys will soon provide tremendous statistical power to constrain the properties of dark energy; however, the constraining power of these surveys will be determined by how well systematic errors are controlled. Of these systematic errors, the dominant one comes from inferring cluster masses using observable signals of clusters, the so-called "observable--mass distribution." This thesis focuses on extracting dark energy information from forthcoming large galaxy cluster surveys, including how we maximize the cosmological information, how we control important systematics, and how precisely we need to calibrate theoretical models. We study how multi-wavelength follow-up observations can improve cluster mass calibration in optical surveys. We also investigate the impact of theoretical uncertainties in calibrating the spatial distributions of galaxy clusters on dark energy constraints. In addition, we explore how the formation history of galaxy clusters impacts the self-calibration of cluster mass. In addition, we use N-body simulations to develop a new statistical sample of cluster-size halos in order to further understand the observable--mass distribution. We study the completeness of subhalos in our cluster sample by comparing them with the satellite galaxies in the Sloan Digital Sky Survey. We also study how subhalo selections impact the inferred correlation between formation time and optical mass tracers, including cluster richness and velocity dispersion.

Download or read book Fundamentals of Galaxy Dynamics Formation and Evolution written by Ignacio Ferreras and published by UCL Press. This book was released on 2019-04-02 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt: Galaxies, along with their underlying dark matter halos, constitute the building blocks of structure in the Universe. Of all fundamental forces, gravity is the dominant one that drives the evolution of structures from small density seeds at early times to the galaxies we see today. The interactions among myriads of stars, or dark matter particles, in a gravitating structure produce a system with fascinating connotations to thermodynamics, with some analogies and some fundamental differences. Ignacio Ferreras presents a concise introduction to extragalactic astrophysics, with emphasis on stellar dynamics, and the growth of density fluctuations in an expanding Universe. Additional chapters are devoted to smaller systems (stellar clusters) and larger ones (galaxy clusters). Fundamentals of Galaxy Dynamics, Formation and Evolution is written for advanced undergraduates and beginning postgraduate students, providing a useful tool to get up to speed in a starting research career. Some of the derivations for the most important results are presented in detail to enable students appreciate the beauty of maths as a tool to understand the workings of galaxies. Each chapter includes a set of problems to help the student advance with the material.

Download or read book Simulations of the evolution of galaxy clusters written by Sabine Schindler and published by . This book was released on 1992 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Planets Stars and Stellar Systems written by Gerard Gilmore and published by Springer. This book was released on 2013-02-23 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is volume 5 of Planets, Stars and Stellar Systems, a six-volume compendium of modern astronomical research, covering subjects of key interest to the main fields of contemporary astronomy. This volume on “Galactic Structure and Stellar Populations”, edited by Gerard F. Gilmore, presents accessible review chapters on Stellar Populations, Chemical Abundances as Population Tracers, Metal-Poor Stars and the Chemical Enrichment of the Universe, The Stellar and Sub-Stellar Initial Mass Function of Simple and Composite Populations, The Galactic Nucleus, The Galactic Bulge, Open Clusters and Their Role in the Galaxy, Star Counts and the Nature of Galactic Thick Disk, The Infrared Galaxy, Interstellar PAHs and Dust, Galactic Neutral Hydrogen, High-Velocity Clouds, Magnetic Fields in Galaxies, Astrophysics of Galactic Charged Cosmic Rays, Gamma-Ray Emission of Supernova Remnants and the Origin of Galactic Cosmic Rays, Galactic Distance Scales, Globular Cluster Dynamical Evolution, Dynamics of Disks and Warps, Mass Distribution and Rotation Curve in the Galaxy, Dark Matter in the Galactic Dwarf Spheroidal Satellites, and History of Dark Matter in Galaxies. All chapters of the handbook were written by practicing professionals. They include sufficient background material and references to the current literature to allow readers to learn enough about a specialty within astronomy, astrophysics and cosmology to get started on their own practical research projects. In the spirit of the series Stars and Stellar Systems published by Chicago University Press in the 1960s and 1970s, each chapter of Planets, Stars and Stellar Systems can stand on its own as a fundamental review of its respective sub-discipline, and each volume can be used as a textbook or recommended reference work for advanced undergraduate or postgraduate courses. Advanced students and professional astronomers in their roles as both lecturers and researchers will welcome Planets, Stars and Stellar Systems as a comprehensive and pedagogical reference work on astronomy, astrophysics and cosmology.

Download or read book The Masses and Dynamics of Galaxy Clusters written by Lyndsay J. Old and published by . This book was released on 2015 with total page 284 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Precision Measurements of the Cluster Red Sequence Using an Error Corrected Gaussian Mixture Model written by and published by . This book was released on 2009 with total page 33 pages. Available in PDF, EPUB and Kindle. Book excerpt: The red sequence is an important feature of galaxy clusters and plays a crucial role in optical cluster detection. Measurement of the slope and scatter of the red sequence are affected both by selection of red sequence galaxies and measurement errors. In this paper, we describe a new error corrected Gaussian Mixture Model for red sequence galaxy identification. Using this technique, we can remove the effects of measurement error and extract unbiased information about the intrinsic properties of the red sequence. We use this method to select red sequence galaxies in each of the 13,823 clusters in the maxBCG catalog, and measure the red sequence ridgeline location and scatter of each. These measurements provide precise constraints on the variation of the average red galaxy populations in the observed frame with redshift. We find that the scatter of the red sequence ridgeline increases mildly with redshift, and that the slope decreases with redshift. We also observe that the slope does not strongly depend on cluster richness. Using similar methods, we show that this behavior is mirrored in a spectroscopic sample of field galaxies, further emphasizing that ridgeline properties are independent of environment. These precise measurements serve as an important observational check on simulations and mock galaxy catalogs. The observed trends in the slope and scatter of the red sequence ridgeline with redshift are clues to possible intrinsic evolution of the cluster red-sequence itself. Most importantly, the methods presented in this work lay the groundwork for further improvements in optically-based cluster cosmology.

Download or read book Clustering in the Universe written by S. Maurogordato and published by Atlantica Séguier Frontières. This book was released on 1995 with total page 622 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Distribution of Star forming Galaxies in Intermediate Redshift Galaxy Clusters written by Steven Michael Crawford and published by . This book was released on 2006 with total page 260 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Observational Constraints on the Assembly of Galaxies and Galaxy Clusters written by Julia Marie Comerford and published by . This book was released on 2009 with total page 330 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Extrinsic Sources of Scatter in the Richness Mass Relation of Galaxy Clusters written by and published by . This book was released on 2012 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: Maximizing the utility of upcoming photometric cluster surveys requires a thorough understanding of the richness-mass relation of galaxy clusters. We use Monte Carlo simulations to study the impact of various sources of observational scatter on this relation. Cluster ellipticity, photometric errors, photometric redshift errors, and cluster-to-cluster variations in the properties of red-sequence galaxies contribute negligible noise. Miscentering, however, can be important, and likely contributes to the scatter in the richness - mass relation of galaxy maxBCG clusters at the low mass end, where centering is more difficult. We also investigate the impact of projection effects under several empirically motivated assumptions about cluster environments. Using SDSS data and the maxBCG cluster catalog, we demonstrate that variations in cluster environments can rarely (≈ 1%-5% of the time) result in significant richness boosts. Due to the steepness of the mass/richness function, the corresponding fraction of optically selected clusters that suffer from these projection effects is ≈ 5%-15%. We expect these numbers to be generic in magnitude, but a precise determination requires detailed, survey-specific modeling.

Download or read book Measuring the Growth of Structure with Multi wavelength Surveys of Galaxy Clusters written by and published by . This book was released on 2008 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt: Current and near-future galaxy cluster surveys at a variety of wavelengths are expected to provide a promising way to obtain precision measurements of the growth of structure over cosmic time. This in turn would serve as an important precision probe of cosmology. However, to realize the full potential of these surveys, systematic uncertainties arising from, for example, cluster mass estimates and sample selection must be well understood. This work follows several different approaches towards alleviating these uncertainties. Cluster sample selection is investigated in the context of arcminute-resolution millimeter-wavelength surveys such as the Atacama Cosmology Telescope (ACT) and the South Pole Telescope (SPT). Large-area, realistic simulations of the microwave sky are constructed and cluster detection is simulated using a multi-frequency Wiener filter to separate the galaxy clusters, via their Sunyaev-Zel'dovich signal, from other contaminating microwave signals. Using this technique, an ACT-like survey can expect to obtain a cluster sample that is 90% complete and 85% pure above a mass of 3 x 10^14 Msun. Cluster mass uncertainties are explored by comparing X-ray and weak-lensing mass estimates for shear-selected galaxy clusters in the Deep Lens Survey (DLS) to study possible biases in using cluster baryons or weak-lensing shear as tracers of the cluster total mass. Results are presented for four galaxy clusters that comprise the top-ranked shear-selected system in the DLS, and for three of these clusters there is agreement between X-ray and weak-lensing mass estimates. For the fourth cluster, the X-ray mass estimate is higher than that from weak-lensing by 2-sigma, and X-ray images suggest this cluster may be undergoing a merger with a smaller cluster, which may be biasing the X-ray mass estimate high. The feasibility of measuring galaxy cluster peculiar velocities using an ACT-like instrument is also investigated. Such a possibility would allow one to measure structure growth via large-scale velocity fields and circumvent the uncertainties associated with measuring cluster masses. We show that such measurements are possible and yield statistical uncertainties of roughly 100 km/sec given either a temperature prior with 1-sigma errors of less than 2 keV or additional lower frequency millimeter-band observations.