Academic literature on the topic 'Cluster of galaxie'

This thesis is focused on design and implementation of procedural generator of galaxy for games or simulations. Second goal is implementation of demonstration application which is showing possible usage of generator. Generator is able to create galaxy by predefined types or by user created map.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2004.<br>Includes bibliographical references (p. 85).<br>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.<br>(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.<br>by Tesla Erin Jeltema.<br>Ph.D.

This thesis is concerned with the role the rich cluster environment plays in the evolution of its galaxy population. We approach this issue from two angles, first we use deep wide-field imaging to investigate the effect of the cluster environment on the spatial and luminosity distribution of galaxies. Secondly, we focus on one particularly interesting class of galaxy, the enigmatic E+A galaxies, using a combination of state-of-the-art telescopes and novel instrumentation to elucidate the physical mechanisms and environmental influences causing the rapid change in star-formation activity in these galaxies. We present results from a deep photometric study of the rich galaxy cluster Abell 2218 (z=0.18) based on Hubble Space Telescope images. These have been used to derive the cluster luminosity function to extremely faint limits. We find the faint-end slope of the luminosity function to vary with environment within the cluster - in the sense that the ratio of `dwarf' galaxies to `giant' galaxies increases in the lower-density outskirt regions. Using imaging obtained with the Isaac Newton Telescope (INT) we confirm the presence of luminosity segregation in Abell 2218. However, luminosity segregation in clusters does not appear to be ubiquitous, with two other clusters studied with the INT (A119 at z=0.04 and A2443 at z=0.11) showing no sign of luminosity segregation of their galaxy populations. We use integral field spectroscopy of a sample of E+A galaxies in intermediate redshift clusters, obtained with the FLAMES system on the European Southern Observatory's VLT and the GMOS instrument on Gemini-North, to determine the radial variation in the strength of Hdelta absorption in these galaxies, and hence map out the distribution of the recently formed stellar population. We find a diversity of behaviour amongst these galaxies in terms of the radial variation in Hdelta absorption: with gradients that are either negative, flat, or positive. By comparing with numerical simulations we suggest that the first of these different types of radial behaviour provides evidence for a merger/interaction origin, whereas the latter two types of behaviour are more consistent with the truncation of star formation in normal disk galaxies.