The Shapes of Galaxy Groups
A. Robotham, S. Phillipps, R. de Propris

TL;DR
This study analyzes the shapes of galaxy groups using probability density functions for their projected axial ratios, revealing a shift from prolate to oblate ellipsoids after correction, and finds good agreement with $ ext{Lambda}$CDM simulations.
Contribution
It provides the first detailed comparison of galaxy group shapes with mock data, showing a transition from prolate to oblate distributions after correction and confirming consistency with cosmological simulations.
Findings
Raw data best fits a prolate ellipsoid with Gaussian axial ratio distribution.
Corrected data favors an oblate ellipsoid with different axial ratio parameters.
Higher multiplicity groups tend to be more spherical.
Abstract
We derive probability density functions for the projected axial ratios of the real and mock 2PIGG galaxy groups, and use this data to investigate the intrinsic three dimensional shape of the dark matter ellipsoids that they trace. As well as analysing the raw data for groups of varying multiplicities, a convolution corrected form of the data is also considered which weights the probability density function according to the results of multiple Monte-Carlo realizations of discrete samples from the input spatial distributions. The important effect observed is that the best fit distribution for all the raw data is a prolate ellipsoid with a Gaussian distribution of axial ratios with and , whilst for the convolved data the best fit solution is that of an oblate ellipsoid and . Previously only prolate distributions were thought…
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Taxonomy
TopicsGalaxies: Formation, Evolution, Phenomena · Scientific Research and Discoveries · Spatial and Panel Data Analysis
