Spherical Collapse in Modified Newtonian Dynamics (MOND)

TL;DR

This paper extends the spherical collapse model within MOND to explain structure formation without dark matter, showing that smaller structures virialize earlier and faster, aligning with observed cosmic structures.

Contribution

It introduces a MOND-based spherical collapse model that accounts for the accelerated formation of small structures without dark matter.

Findings

Smaller structures virialize earlier in MOND

Virialization occurs gradually from center to outer layers

Smaller structures have stronger gravitational acceleration

Abstract

Modeling the structure formation in the universe, we extend the spherical collapse model in the context of MOND starting with the linear Newtonian structure formation followed by the MONDian evolution. In MOND the formation of structures speed up without a need for dark matter. Starting with the top-hat over-dense distribution of the matter, the structures virialize with a power--law profile of the distribution of matter. We show that the virialization process takes place gradually from the center of the structure to the outer layers. In this scenario the smaller structures enter to the MONDian regime earlier and evolve faster, hence they are older than larger structures. We also show that the virialization of the structures occur in the MONDian regime, in which the smaller structures have stronger gravitational acceleration than the larger ones. This feature of the dynamical behavior of the structures is in agreement with this fact that the smaller structures as the globular clusters or galactic bulges have been formed earlier and need less dark matter in CDM scenario.