Euclid preparation. XXXIX. The effect of baryons on the Halo Mass Function (2311.01465v2)

Abstract: The Euclid photometric survey of galaxy clusters stands as a powerful cosmological tool, with the capacity to significantly propel our understanding of the Universe. Despite being sub-dominant to dark matter and dark energy, the baryonic component in our Universe holds substantial influence over the structure and mass of galaxy clusters. This paper presents a novel model to precisely quantify the impact of baryons on galaxy cluster virial halo masses, using the baryon fraction within a cluster as proxy for their effect. Constructed on the premise of quasi-adiabaticity, the model includes two parameters calibrated using non-radiative cosmological hydrodynamical simulations and a single large-scale simulation from the Magneticum set, which includes the physical processes driving galaxy formation. As a main result of our analysis, we demonstrate that this model delivers a remarkable one percent relative accuracy in determining the virial dark matter-only equivalent mass of galaxy clusters, starting from the corresponding total cluster mass and baryon fraction measured in hydrodynamical simulations. Furthermore, we demonstrate that this result is robust against changes in cosmological parameters and against varying the numerical implementation of the sub-resolution physical processes included in the simulations. Our work substantiates previous claims about the impact of baryons on cluster cosmology studies. In particular, we show how neglecting these effects would lead to biased cosmological constraints for a Euclid-like cluster abundance analysis. Importantly, we demonstrate that uncertainties associated with our model, arising from baryonic corrections to cluster masses, are sub-dominant when compared to the precision with which mass-observable relations will be calibrated using Euclid, as well as our current understanding of the baryon fraction within galaxy clusters.

• The paper demonstrates that baryonic corrections can be modeled with about 1% accuracy in virial mass estimates of galaxy clusters.
• It employs advanced hydrodynamical simulations (Magneticum and TNG300) to calibrate baryonic impacts via quasi-adiabatic models and varying AGN feedback.
• The findings enhance the reliability of cosmological parameter estimation by integrating baryonic physics into galaxy cluster analyses.

The Effect of Baryons on the Halo Mass Function: Implications for Cosmological Studies

This paper, prepared by the Euclid Collaboration, presents a comprehensive analysis of baryonic effects on the halo mass function (HMF) for galaxy clusters, with a specific focus on its implications for cosmological studies. The paper emphasizes the necessity to account for baryonic physics when inferring cosmological parameters from galaxy cluster surveys such as those planned for the Euclid space mission. Below, I provide a detailed summary and critique of the methodologies, results, and scientific implications presented within this investigation.

Methodology

The research employs a robust model to quantify the impact of baryons on the virial masses of galaxy clusters. It builds on cosmological hydrodynamical simulations, specifically leveraging the Magneticum and TNG300 suite of simulations, to calibrate the effects. The methodology is grounded in the premise of quasi-adiabatic changes driven by baryonic processes, conceptualized through two main parameters: a quasi-adiabatic factor and a baryonic offset. These parameters are meticulously calibrated using non-radiative and full-physics simulations. The paper also explores variations in AGN feedback strength to evaluate model robustness across different baryonic feedback scenarios.

Numerical Results

A key result of the paper is the demonstration that baryonic effects can be modeled with a high degree of precision, achieving a relative accuracy of approximately 1% in determining the virial dark matter-only (DMO) equivalent mass. This highlights the model's robustness across varying cosmic baryon fractions and feedback scenarios. The subdominance of baryonic corrections, as compared to the uncertainties in mass-observable relations measured by Euclid, further underscores the model's applicability in future cosmological analyses.

Simulation Insights

The research provides valuable insights from the extensive suite of simulations, revealing notable differences in baryonic depletion between different simulation setups. Specifically, the Magneticum simulations show a more considerable baryonic depletion relative to the cosmic value when compared to TNG300. The authors discuss the potential implications of these differences on halo mass estimation and the subsequent inference of cosmological parameters, advocating for corrections to avoid biases in cosmological constraints derived from observational data.

Implications and Future Directions

The paper's consistency across multiple simulations and baryonic feedback models offers a reliable framework for integrating baryonic corrections into cosmology analyses. This work sets the stage for more precise cosmological parameter estimation by including the previously overlooked impacts of baryonic physics. While the research acknowledges current gaps in understanding subresolution physics, particularly in AGN feedback, it also suggests pathways for future improvements, including the incorporation of non-adiabatic processes and a broader range of baryonic models.

Furthermore, the significance of accurate baryonic modeling becomes evident when examining the potential biases in cosmological constraints without such corrections. The paper highlights the critical role of modeling baryonic physics in harmonizing observations of galaxy clusters with theoretical predictions, thereby enhancing the fidelity of future cosmological surveys.

In conclusion, the research presented in this paper provides a substantial contribution to the field of cosmological surveys by addressing and modeling the impact of baryons on galaxy cluster analysis. The work establishes a foundation for future studies to refine the model further and account for baryonic effects, thereby ensuring robust cosmological parameter estimation from upcoming observational data. The Euclid Collaboration's efforts demonstrate a pathway to overcoming traditional challenges in clustering statistics and offer a robust approach for advancing the precision of large-scale structure investigations.