The parallelism between galaxy clusters and early-type galaxies: III. The Mass-Radius Relationship

TL;DR

This study explores the physical origins of the Mass-Radius Relationship across various stellar systems, revealing that their distribution results from combined stellar and halo evolution influenced by virial equilibrium and halo mass limits.

Contribution

It provides a comprehensive analysis linking the observed Mass-Radius Relation to theoretical models of galaxy and cluster formation, integrating stellar and halo evolution mechanisms.

Findings

Distribution in the MR-plane results from virial equilibrium and star formation history.

The maximum halo mass at each epoch constrains the MR distribution.

The curved distribution and zone of avoidance are explained by combined evolution processes.

Abstract

Context. This is the third study of a series dedicated to the observed parallelism of properties between Galaxy Clusters and Groups(GCGs) and early-type galaxies (ETGs). Aims. Here we investigate the physical origin of the Mass-Radius Relation (MRR). Methods. Having collected literature data on masses and radii for objects going from Globular Clusters (GCs) to ETGs and GCGs, we set up the MR-plane and compare the observed distribution with the MRR predicted by theoretical models both for the monolithic and hierarchical scenarios. Results. We argue that the distributions of stellar systems in the MR-plane is due to complementary mechanisms: (i) on one hand, as shown in paper II, the relation of the virial equilibrium does intersect with a relation that provides the total luminosity as a function of the star formation history; (ii) on the other hand, the locus predicted for the collapse of systems should be convolved with the statistical expectation for the maximum mass of the halos at each comsic epoch. This second aspect provides a natural boundary limit explaining either the curved distribution observed in the MR-plane and the existence of a zone of avoidance. Conclusions. The distribution of stellar systems in the MR-plane is the result of two combined evolution, that of the stellar component and that of the halo component.