The evolving role of astrophysical modelling in dark matter halo relaxation response

TL;DR

This paper investigates how baryonic processes influence dark matter halo relaxation in cosmological simulations across different epochs, highlighting the importance of feedback energy flux and gas physics in shaping halo responses.

Contribution

It demonstrates that a linear quasi-adiabatic model describes halo relaxation well at multiple redshifts and identifies key baryonic parameters affecting this response across diverse simulations.

Findings

Relaxation response is well-described by a linear quasi-adiabatic model at z=0 and z=1.

Feedback energy flux significantly influences halo relaxation, while wind speed and burstiness do not.

Gas equation of state strongly impacts the relaxation response, especially in EAGLE simulations.

Abstract

We study the change in the radial distribution of dark matter within haloes in response to baryonic astrophysical processes in galaxies at different epochs, investigating the role of astrophysical modeling in cosmological hydrodynamic simulations in producing the response. We find that the linear quasi-adiabatic relaxation with additional dependence on the halo-centric distance provides a good description not only at $z=0$, but also at an earlier epoch ($z=1$) in the IllustrisTNG simulation suite, with parameters being more universal across a much larger variety of haloes at $z=1$ than at $z=0$. Through systematic analysis of a large collection of simulations from the CAMELS project, we find that the baryonic prescriptions for both AGN and stellar feedbacks have a strong influence on the relaxation response of the dark matter halo. In particular, only the parameters controlling the overall feedback energy flux have an effect on the relaxation response, while the wind speed and burstiness have negligible effect on the relaxation at a fixed amount of energy flux. However, the exact role of these parameters on the relaxation depends on the redshift. We also study the role of a variety of baryonic astrophysical processes through the EAGLE physics variation simulations. While these depict a similar picture regarding the importance of feedback effects, they also reveal that the gas equation of state has one of the strongest influences on the relaxation response, consistent with the expectation from self-similar analyses.