The extent of gravitationally bound structure in a {\Lambda}CDM universe

TL;DR

This paper introduces a new analytical model based on a modified spherical collapse model to better predict the extent of gravitationally bound structures in a {}CDM universe, validated against simulations and real supercluster data.

Contribution

A novel modified spherical collapse model with a critical parameter =1.89 that improves prediction accuracy of bound structures compared to previous models.

Findings

The new model better identifies gravitationally bound structures in simulations.

Predictions for the Corona Borealis supercluster align with recent observational studies.

Mass estimates within the Virgo cluster's turnaround radius agree with existing mass measurements.

Abstract

A new analytical model for constraining the extent of gravitationally bound structure in the Universe is presented. This model is based on a simple modification of the spherical collapse model (SCM), and its performance in predicting the limits of bound structure in N-body simulations is compared to that of two previous models with the aid of new software named COLDGaS-- compute unified device architecture (CUDA) object location determination in GADGET2 snapshots -- which was developed by the author. All of these models can be distilled down to a single unique parameter {\xi}, here named the critical parameter, which was found to have values of 3 and 1.18 from the previous studies, and a value of 1.89 from the modified SCM. While still on the conservative side, this new model tends to better identify what structure is gravitationally bound in simulations. All three analytical models are applied to the Corona Borealis supercluster, with the modified SCM and {\xi} = 1.18 model making predictions that are in agreement with recent work showing that A2056, A2061, A2065, A2067, and A2089 comprise a gravitationally bound supercluster. As an additional test, the modified SCM is used to estimate the mass within the turn around radius of the Virgo cluster, providing results in good agreement with studies relating the virial mass of clusters to the total mass within turn around.