The Shapes of Galaxy Clusters

Abstract

We have reanalyzed a data set of 99 low redshift ($z<0.1$) Abell clusters and determined their shapes. For this, three different measures are used. We use Monte-Carlo simulations to investigate the errors in the methods. The corrected distribution of cluster ellipticities shows a peak at $\epsilon \sim 0.4$ and extends to $\epsilon \sim 0.8$. The results are self-consistent, i.e., with the corrected distribution over projected cluster shapes we can reconstruct the observed distribution and the observed relation between the number of galaxies in a cluster and its ellipticity. It is shown that the richer clusters are intrinsically more nearly spherical than the poorer ones. The corrected distribution of cluster shapes is more consistent with a prolate population than with an oblate population. We compare the corrected true distribution of (projected) ellipticities with predictions from N-body simulations. For this, we use a catalogue of 75 N-body simulated clusters (van Kampen 1994) which assume a CDM spectrum with $\Omega =1.0$. The simulations include a recipe for galaxy formation and merging. 'Observing' these simulated clusters produces an ellipticity distribution that extends to much higher $\epsilon$ and that has too few nearly spherical clusters. Preliminary results of simulations of the formation of clusters in an $\Omega =0.2$ universe suggest that, on average, clusters are more nearly spherical in this case.

17 pages, postscript, submitted to MNRAS

Cited by in corpus (34)

• Shapes and Alignments of Galaxy Cluster Halos
• The velocity and mass distribution of clusters of galaxies from the CNOC1 cluster redshift survey
• Direct measurement of dark matter halo ellipticity from two-dimensional lensing shear maps of 25 massive clusters
• Cluster Alignments and Ellipticities in LCDM Cosmology
• The ESO Nearby Abell Cluster Survey. XII. The mass and mass-to-light-ratio profiles of rich clusters
• The Three-Dimensional Shapes of Galaxy Clusters
• RASS-SDSS Galaxy Cluster Survey. VII. On the Cluster Mass to Light ratio and the Halo Occupation Distribution
• A Detection of Dark Matter Halo Ellipticity using Galaxy Cluster Lensing in SDSS
• The Velocity Dispersion of MS1054-03: A Massive Galaxy Cluster at High Redshift
• Testing linear-theory predictions of galaxy formation
• The Morphologies and Alignments of Gas, Mass, and the Central Galaxies of CLASH Clusters of Galaxies
• Alignments of Galaxy Group Shapes with Large Scale Structure
• Measuring the Three-Dimensional Structure of Galaxy Clusters. II. Are clusters of galaxies oblate or prolate?
• Mass, shape and thermal properties of A1689 by a multi-wavelength X-ray, lensing and Sunyaev-Zel'dovich analysis
• The Ellipticity and Orientation of Clusters of Galaxies from N-Body Experiments
• The Apparent and Intrinsic Shape of the APM Galaxy Clusters
• Dynamical mass inference of galaxy clusters with neural flows
• On the deprojection of clusters of galaxies combining X-ray, Sunyaev-Zeldovich temperature decrement and gravitational lensing maps
• CLASH-VLT: Testing the Nature of Gravity with Galaxy Cluster Mass Profiles
• On the over-concentration problem of strong lensing clusters
• CLUMP-3D. Three dimensional lensing and multi-probe analysis of MACS J1206.2-0847, a remarkably regular cluster
• Cluster Ellipticities as a Cosmological Probe
• Cosmic voids detection without density measurements
• Shape and orientation of the gas distribution in A1689
• Morphological & Dynamical Properties of low redshift 2dFGRS Groups
• Phase-space shapes of clusters and rich groups of galaxies
• Fossil Group Origins VII. Galaxy substructures in fossil systems
• Recent Dynamical Relaxation of Galaxy Clusters: Evidence for a Low-${\Omega }_m$ Universe
• The Relation between Morphology and Dynamics of Poor Groups of Galaxies
• HST Observations of the Gravitationally Lensed Cloverleaf Broad Absorption Line QSO H1413+1143: Modeling the Lens
• Morphology of low-redshift compact galaxy clusters I. Shapes and radial profiles
• Distortion of Globular Clusters by Galactic Bulges
• Dynamics of the galactic component of Abell S1063 and MACS J1206.2$-$0847
• More relaxed intracluster gas than galaxies in clusters in quasi-equilibrium