Halo mass functions in mixed cold and fuzzy dark matter models
Abstract
We investigate the impact of mixed cold and fuzzy dark matter (MDM) cosmologies on the halo mass function (HMF) using numerical simulations performed with the AxiREPO framework. We consider models in which an ultralight axion-like component with mass m =10−24.5 eV constitutes a fraction f ≤ 0.3 of the total dark matter. To enable consistent halo identification in mixed-species scenarios, we develop a grid-based halo-finding pipeline that combines the particle-based cold dark matter (CDM) and wave-like fuzzy dark matter (FDM) components into a unified density field. We find that FDM traces the large-scale CDM distribution while suppressing small-scale structure through wave interference effects, leading to a reduction in the abundance of low-mass haloes and modifying the HMF in a manner dependent on redshift and FDM fraction. Increasing the FDM fraction produces a systematic downward shift in the HMF and modifies its high-mass slope. Motivated by these trends, we introduce a phenomenological model that maps CDM HMFs to their MDM counterparts using a suppression function with parameters dependent on redshift and FDM fraction. This model reproduces the simulated HMFs within approximately 0.1 to 0.2 dex across the parameter space explored (1 ≤ z ≤ 4, f ≤ 0.3). Our results provide a computationally efficient method for predicting structure formation in MDM cosmologies without requiring dedicated simulations for each parameter choice, and establish a framework for exploring the impact of MDM on cosmological structure formation.
Related
- Temporal Correlations Between Fuzzy Dark Matter and Baryonic Matter in Virialized Core-Halo Structures
- A unified stochastic random walk theory for Kolmogorov spectrum, halo mass functions, and halo density profiles
- Hydrostatic Equilibrium Constraints on the Fuzzy Dark Matter Mass from Dwarf Spheroidals: Method, Systematics, and Robustness
- Constraints on the fuzzy dark matter mass using globular clusters in dwarf galaxies from Euclid ERO data
- A Unified Halo Mass Function Across Dark Matter Models from High-Resolution Multi-Scale Simulations
BibTeX
@misc{johnston2026halo,
title = {{Halo mass functions in mixed cold and fuzzy dark matter models}},
author = {Sarah C. Johnston and Simon May and Tibor Dome and Sownak Bose and Alastair Basden and Carlton Baugh and Anastasia Fialkov and Alex Tocher},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2606.06599},
eprint = {2606.06599},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2606.06599},
}
RIS
TY - UNPB
TI - Halo mass functions in mixed cold and fuzzy dark matter models
AU - Sarah C. Johnston
AU - Simon May
AU - Tibor Dome
AU - Sownak Bose
AU - Alastair Basden
AU - Carlton Baugh
AU - Anastasia Fialkov
AU - Alex Tocher
PY - 2026
DA - 2026/10/05
PB - arXiv
DO - 10.48550/arxiv.2606.06599
UR - https://arxiv.org/abs/2606.06599
AB - We investigate the impact of mixed cold and fuzzy dark matter (MDM) cosmologies on the halo mass function (HMF) using numerical simulations performed with the AxiREPO framework. We consider models in which an ultralight axion-like component with mass m =10^−24.5 eV constitutes a fraction f ≤ 0.3 of the total dark matter. To enable consistent halo identification in mixed-species scenarios, we develop a grid-based halo-finding pipeline that combines the particle-based cold dark matter (CDM) and wave-like fuzzy dark matter (FDM) components into a unified density field. We find that FDM traces the large-scale CDM distribution while suppressing small-scale structure through wave interference effects, leading to a reduction in the abundance of low-mass haloes and modifying the HMF in a manner dependent on redshift and FDM fraction. Increasing the FDM fraction produces a systematic downward shift in the HMF and modifies its high-mass slope. Motivated by these trends, we introduce a phenomenological model that maps CDM HMFs to their MDM counterparts using a suppression function with parameters dependent on redshift and FDM fraction. This model reproduces the simulated HMFs within approximately 0.1 to 0.2 dex across the parameter space explored (1 ≤ z ≤ 4, f ≤ 0.3). Our results provide a computationally efficient method for predicting structure formation in MDM cosmologies without requiring dedicated simulations for each parameter choice, and establish a framework for exploring the impact of MDM on cosmological structure formation.
ER -