Counts-in-Cells of subhaloes in the IllustrisTNG simulations: the role of baryonic physics

TL;DR

This study analyzes the Counts-in-Cells statistics of subhaloes in the IllustrisTNG simulations, demonstrating that the GQED model effectively describes baryonic and dark matter distributions across various redshifts and scales.

Contribution

It evaluates and compares the GQED and NBD models for subhalo distributions in full and dark-only simulations, extending understanding of baryonic effects on large-scale structure statistics.

Findings

Both models fit the data well with minor differences due to baryons.

The GQED model's assumptions remain valid with baryonic physics.

The density-in-cells PDF aligns with previous theoretical predictions.

Abstract

We present an analysis of the Counts-in-Cells (CiC) statistics of subhaloes in the publicly available IllustrisTNG cosmological simulations (TNG100-1, TNG100-3 and TNG300-3), considering their full and dark-only versions, in redshifts ranging from $z = 0$ to $z=5$, and different cell sizes. We evaluated two CiC models: the gravitational quasi-equilibrium distribution (GQED) and the negative binomial distribution (NBD), both presenting good fits, with small detectable differences in the presence of baryons. Scaling and time dependencies of the best-fit parameters showed similar trends compared with the literature. We derived a matter density-in-cells probability distribution function (PDF), associated with the GQED, which was compared to the PDF given in Uhlemann et al. (2016), for the IllustrisTNG 100-3-Dark run at $z=0$. Our results indicate that the simplest gravithermodynamical assumptions of the GQED model hold in the presence of baryonic dissipation. Interestingly, the smoothed (density-in-cells) version of the GQED is also adequate for describing the dark matter one-point statistics of subhaloes and converges, to subpercentage levels (for an interval of parameters), to the Uhlemann et al. PDF in the high density range.