Shapes and Probabilities of Galaxy Clusters

Abstract

We develop a general theory for estimating the probability that a galaxy cluster of a given shape exists. The theory is based on the observed result that the distribution of galaxies is very close to quasi-equilibrium, in both its linear and nonlinear regimes. This places constraints on the spatial configuration of a cluster of galaxies in quasi-equilibrium. In particular, we show that that a cluster of galaxies may be described as a collection of nearly virialized subclusters of approximately the same mass. Clusters that contain more than 10 subclusters are very likely to be completely virialized. Using our theory, we develop a method for comparing probabilities of different spatial configurations of subclusters. As an illustrative example, we show that a cluster of galaxies arranged in a line is more likely to occur than a cluster of galaxies arranged in a ring.

Shapes and Probabilities of Galaxy Clusters. Ii. Comparisons With Observations

“…The GQED therefore describes the clustering of galaxies with no free parameters. The implications of this physical description for the shapes of clusters was studied in Yang & Saslaw (2012, paper 1), which provided a method for determining the probability that a cell with N galaxies has a particular kinetic energy and correlation potential energy. This method uses the statistical mechanics of the GQED to describe the probability that a cell has a given kinetic energy and correlation potential energy, and is based on earlier work by Leong & Saslaw (2004).…”

“…This paper is structured as follows: In section 2 we describe the theoretical background with reference to earlier work by Yang & Saslaw (2012) which we refer to as paper 1. In particular, we analyze the relation between the kinetic energy, gravitational correlation potential energy and total energy within the framework of the GQED.…”

Sympathetic Eruptions of Two Filaments with an Identifiable Causal Link Observed by the Solar Dynamics Observatory

“…In addition to the filament eruptions mentioned above, sympathetic eruptions between filaments are also ubiquitous. These eruptions are defined as consecutive filament eruptions occurring within a short time in different locations but having a certain physical connection Jiang et al 2014;Yang et al 2012;Wang et al 2016;Joshi et al 2016;Li et al 2017). Two filaments, which reside above different PILs and share the same overlying magnetic system, could interact sympathetically, i.e., the first erupting filament disturbs the magnetic system of the second filament and leads to its eruption (Shen et al 2012).…”

Unraveling the Links among Sympathetic Eruptions

“…The long-distance coupling may result from the impact of CMEs, waves, or propagating perturbations (e.g., Wang et al 2001;Jiang et al 2008;Török et al 2011;Lynch & Edmondson 2013;Jin et al 2016). A crucial physical link between sympathetic eruptions is often proposed to be magnetic reconnection of large-scale magnetic field as induced indirectly or directly by distant or nearby eruptions: the reconnection may effectively modify the overlying field that provides the confining force for a pre-eruptive structure underneath, as suggested in numerous observational investigations (Liu et al 2009a;Zuccarello et al 2009;Jiang et al 2011;Shen et al 2012;Yang et al 2012;Joshi et al 2016;Wang et al 2016) and corroborated by a few numerical simulations (Ding et al 2006;Török et al 2011;Lynch & Edmondson 2013). The consequence of the reconnection is occasionally observed as coronal dimming (Jiang et al 2011) when the overlying field is partially removed by reconnection.…”