Joint Constraints on Fuzzy and Warm Dark Matter from Satellite Populations of the Milky Way and Andromeda

TL;DR

This work addresses small-scale challenges to cold dark matter by jointly constraining fuzzy dark matter and thermal-relic warm dark matter using satellite populations in the Milky Way and Andromeda. The authors implement a galaxy–halo connection model fed by high-resolution CDM zoom-in simulations and incorporate non-CDM suppression through transfer-function–based subhalo abundances, folded with detailed survey selection functions. By jointly analyzing MW and M31 satellites from DES, PS1, and PAndAS, and accounting for host-mass uncertainties, they obtain the strongest Local Group constraints to date: $m_{ ext{FDM}} > 1.75 imes 10^{-20}$ eV (95% CL) and $m_{ ext{WDM}} > 6.22$ keV (95% CL), with ~10% improvements over MW-only analyses. These results sharpen the role of satellite populations as probes of non-CDM physics and pave the way for even tighter bounds with upcoming surveys and more precise host-mass measurements.

Abstract

We perform a joint analysis of the Milky Way (MW) and Andromeda (M31) satellite populations to constrain the properties of fuzzy dark matter (FDM) and thermal-relic warm dark matter (WDM). We combine MW satellite observations from the Dark Energy Survey (DES) and Pan-STARRS1 (PS1) with M31 satellite data from the Pan-Andromeda Archaeological Survey (PAndAS), and model the corresponding observable satellite populations using the galaxy--halo connection model together with the appropriate selection functions. Uncertainties in the virial masses of the MW and M31 are incorporated through host-mass priors that linearly scale the relevant model parameters, allowing us to infer the full posterior distributions of all parameters. For the FDM case, we obtain $m_{\mathrm{FDM}} > 1.75 \times 10^{-20}~\mathrm{eV}$ (95% CL) and $m_{\mathrm{FDM}} > 1.41 \times 10^{-20}~\mathrm{eV}$ (20:1 posterior ratio). For thermal-relic WDM, we find $m_{\mathrm{WDM}} > 6.22~\mathrm{keV}$ (95% CL) and $m_{\mathrm{WDM}} > 5.75~\mathrm{keV}$ (20:1 posterior ratio). These results represent a moderate improvement over MW-only constraints, and provide the strongest constraints to date on the FDM and WDM derived from satellite galaxy populations in the Local Group.

Figures (8)

• Figure 1: The left and right panels show the transfer functions and subhalo mass function suppressions for FDM (blue) and WDM (orange), respectively. In the left panel, the lower $x$-axis indicates the cosmological wavenumber, while the upper $x$-axis shows the corresponding halo mass. In the right panel, the $x$-axis represents the peak virial mass. Different line styles correspond to different particle masses, and models with the same line style have the same half-mode mass $M_{\mathrm{hm}}$. The solid and dashed curves correspond to $M_{\mathrm{hm}} = 4.30\times10^{8}~M_\odot$ and $3.64\times10^{7}~M_\odot$, respectively.
• Figure 2: The half-light radii $r_{1/2}$ of the satellite galaxy data we use as a function of the absolute magnitudes $M_V$. The blue dots, orange triangles, and green squares mark the satellites from the DES, PS1, and PAndAS, respectively.
• Figure 3: The PDF and contour maps (68% and 95% CLs) of the shared parameters in the FDM model. The shaded regions in the one-dimensional PDFs and the quoted parameter values correspond to 68% CL. The parameters $\mathcal{M}_{50}$ and $M_{\mathrm{hm}}$ are in units of $M_\odot$, and $\sigma_\mathrm{gal}$ is in dex.
• Figure 4: Same as Figure \ref{['Joint_sp_m_single_fdm.pdf']}, but for the WDM case.
• Figure 5: Luminosity functions of satellites located between 30 and 300 kpc from the centers of the MW (blue) and M31 (gray), based on the FDM results from our modeling framework. Dark and light shaded regions show the 68% and 95% CLs, and the black solid lines denotes the mean predicted luminosity functions.