DM haloes in the fifth-force cosmology

TL;DR

This study explores how a fifth force, modeled as a scalar interaction, influences dark matter halo properties, revealing increased concentration, sphericity, and virialization compared to standard cosmology.

Contribution

It demonstrates the effects of long-range scalar interactions on dark matter haloes using high-resolution simulations, highlighting differences from the standard b1CDM model.

Findings

ReBEL haloes have higher concentrations than b1CDM haloes.

Dark matter haloes are more spherical in ReBEL models.

ReBEL haloes are more virialized, especially with stronger fifth forces.

Abstract

We investigate how long-range scalar interactions affect the properties of dark matter haloes. For doing so we employ the ReBEL model which implements an additional interaction between dark matter particles. On the phenomenological level this is equivalent to a modification of gravity. We analyse the differences between five ReBEL models and $\Lambda$CDM using a series of high resolution cosmological simulations. Emphasis is placed on investigating how halo properties change in the presence of a fifth force. We report that the density profile of ReBEL haloes is well described by the NFW profile but with mean concentrations from $5\%$ to a few times higher than the standard $\Lambda$CDM value. We also find a slight increase of the halo spin for haloes more massive than $5\times10^{11}\M_{\odot}$, reflecting a higher rotational support of those haloes due to scalar forces. In addition, the dark matter haloes in our models are more spherical than their counterparts in $\Lambda$CDM. The ReBEL haloes are also more virialised, with a large difference from $\Lambda$CDM for strong fifth forces and a much smaller change for weak scalar interactions.