Characterizing dark interactions with the halo mass accretion history and structural properties

TL;DR

This paper investigates how dark energy interactions influence the growth and internal structure of dark matter haloes, using simulations to develop models that predict halo properties across different cosmological scenarios.

Contribution

It introduces an accurate MAH model for coupled dark energy cosmologies and explores how halo concentration and substructure vary with dark interactions and {\sigma}_8.

Findings

MAH model reproduces halo growth within 10% for weak cDE models

Complex cDE models show rapid high-redshift halo growth not captured by simple rescaling

Halo concentration increases in cDE scenarios with fixed {\sigma}_8

Abstract

We study the halo mass accretion history (MAH) and its correlation with the internal structural properties in coupled dark energy cosmologies (cDE). To accurately predict all the non-linear effects caused by dark interactions, we use the COupled Dark Energy Cosmological Simulations (CoDECS). We measure the halo concentration at z=0 and the number of substructures above a mass resolution threshold for each halo. Tracing the halo merging history trees back in time, following the mass of the main halo, we develope a MAH model that accurately reproduces the halo growth in term of M_{200} in the {\Lambda}CDM Universe; we then compare the MAH in different cosmological scenarios. For cDE models with a weak constant coupling, our MAH model can reproduce the simulation results, within 10% of accuracy, by suitably rescaling the normalization of the linear matter power spectrum at z=0, {\sigma}_8. However, this is not the case for more complex scenarios, like the "bouncing" cDE model, for which the numerical analysis shows a rapid growth of haloes at high redshifts, that cannot be reproduced by simply rescaling the value of {\sigma}_8. Moreover, at fixed value of {\sigma}_8, cold dark matter (CDM) haloes in these cDE scenarios tend to be more concentrated and have a larger amount of substructures with respect to {\Lambda}CDM predictions. Finally, we present an accurate model that relates the halo concentration to the time at which it assembles half or 4% of its mass. Combining this with our MAH model, we show how halo concentrations change while varying only {\sigma}_8 in a {\Lambda}CDM Universe, at fixed halo mass.