Degeneracies between Modified Gravity and Baryonic Physics

TL;DR

This study investigates how modified gravity theories, specifically the Symmetron model, can produce observable effects that are degenerate with baryonic physics processes in cosmological simulations, complicating their distinction.

Contribution

It introduces a systematic analysis of degeneracies between modified gravity and baryonic physics using hydrodynamic simulations with varied models and processes.

Findings

Degeneracies exist between Symmetron parameters and baryonic processes.

Radiative processes can mimic effects of modified gravity.

Simulations reveal challenges in distinguishing gravity modifications from baryonic effects.

Abstract

In order to determine the observable signatures of modified gravity theories, it is important to consider the effect of baryonic physics. We use a modified version of the ISIS code to run cosmological hydrodynamic simulations to study degeneracies between modified gravity and radiative hydrodynamical processes. Of these, one was the standard $\Lambda$CDM model and four were variations of the Symmetron model. For each model we ran three variations of baryonic processes: non-radiative hydrodynamics; cooling and star formation; and cooling, star formation, and supernova feedback. We construct stacked gas density, temperature, and dark matter density profiles of the halos in the simulations, and study the differences between them. We find that both radiative variations of the models show degeneracies between their processes and at least two of the three parameters defining the Symmetron model.