[Paper Review] Astrophysical Tests of Dark Matter with Maunakea Spectroscopic Explorer

Ting S. Li, Manoj Kaplinghat+28 more|arXiv (Cornell University)|Mar 7, 2019

Stellar, planetary, and galactic studiesPhysics and Astronomy28 references3 citations

TL;DR

This paper proposes that the Maunakea Spectroscopic Explorer (MSE), with its high multiplexing (4,300 fibers), wide field-of-view (1.5 deg²), and 11.25m aperture, will enable transformative astrophysical tests of dark matter particle physics by mapping dark matter halos across all mass scales. By measuring stellar kinematics, phase-space distributions, and density profiles in the Milky Way, its satellites, and low-redshift galaxies, MSE will probe deviations from cold, collisionless dark matter, improving direct and indirect detection constraints and testing self-interacting, warm, and fuzzy dark matter models.

ABSTRACT

We discuss how astrophysical observations with the Maunakea Spectroscopic Explorer (MSE), a high-multiplexity (about 4300 fibers), wide field-of-view (1.5 square degree), large telescope aperture (11.25 m) facility, can probe the particle nature of dark matter. MSE will conduct a suite of surveys that will provide critical input for determinations of the mass function, phase-space distribution, and internal density profiles of dark matter halos across all mass scales. N-body and hydrodynamical simulations of cold, warm, fuzzy and self-interacting dark matter suggest that non-trivial dynamics in the dark sector could have left an imprint on structure formation. Analysed within these frameworks, the extensive and unprecedented datasets produced by MSE will be used to search for deviations away from cold and collisionless dark matter model. MSE will provide an improved estimate of the local density of dark matter, critical for direct detection experiments, and will improve estimates of the J-factor for indirect searches through self-annihilation or decay into Standard Model particles. MSE will determine the impact of low mass substructures on the dynamics of Milky Way stellar streams in velocity space, and will allow for estimates of the density profiles of the dark matter halos of Milky Way dwarf galaxies using more than an order of magnitude more tracers. In the low redshift Universe, MSE will provide critical redshifts to pin down the luminosity functions of vast numbers of satellite systems, and MSE will be an essential component of future strong lensing measurements to constrain the halo mass function. Across nearly all mass scales, the improvements offered by MSE, in comparison to other facilities, are such that the relevant analyses are limited by systematics rather than statistics.

Motivation & Objective

• To leverage MSE’s unprecedented spectroscopic capabilities to probe the particle nature of dark matter beyond the standard cold, collisionless model.
• To improve constraints on the local dark matter density and J-factors critical for direct and indirect detection experiments.
• To map the phase-space distribution and internal density profiles of dark matter halos in the Milky Way and its dwarf satellites with orders-of-magnitude more tracers.
• To test predictions of alternative dark matter models—self-interacting (SIDM), warm (WDM), and fuzzy (FDM)—through astrophysical observables such as substructure, stream kinematics, and halo offsets.
• To reduce systematics in dark matter halo mass function and luminosity function measurements by achieving high spatial and temporal completeness in surveys.

Proposed method

• Utilize MSE’s 4,300-fiber spectroscopy to obtain redshifts and velocity dispersions for stars in Milky Way stellar streams, dwarf galaxies, and satellite systems.
• Apply high-resolution kinematic modeling to infer the gravitational potential and dark matter halo density profiles from phase-space distributions of tracers.
• Combine MSE data with strong lensing maps and X-ray/gas kinematics to measure offsets between baryonic and dark matter peaks in merging clusters.
• Use N-body and hydrodynamical simulations of alternative dark matter models (SIDM, WDM, FDM) to predict observable imprints such as core formation, wobbling of brightest cluster galaxies, and stream substructure.
• Perform ensemble analyses of BCG wobbling and subhalo offsets in relaxed clusters to constrain self-interaction cross sections.
• Integrate MSE redshifts with LSST photometry to measure the faint-end galaxy luminosity function and satellite halo mass functions with high completeness.

Experimental results

Research questions

• RQ1 Can MSE detect deviations from cold dark matter in the phase-space distribution and density profiles of Milky Way stellar streams and dwarf galaxies?
• RQ2 To what extent can MSE improve the precision of the local dark matter density and J-factor for direct and indirect detection experiments?
• RQ3 Can MSE identify signatures of self-interacting dark matter through kinematic wobbling of brightest cluster galaxies or subhalo offsets in merging clusters?
• RQ4 How do the kinematics of low-mass substructures in the Milky Way halo imprint on the velocity structure of stellar streams, and can MSE resolve these features?
• RQ5 Can MSE’s high-fidelity redshifts enable robust constraints on the faint-end of the galaxy luminosity function and the halo mass function in low-redshift environments?

Key findings

• MSE will provide more than an order of magnitude greater number of tracers for mapping dark matter halo density profiles in Milky Way dwarf galaxies, enabling precise constraints on their internal structure.
• The survey will improve estimates of the local dark matter density to better than 10% precision, significantly enhancing sensitivity for direct detection experiments.
• MSE will reduce systematics in J-factor measurements for ultra-faint dwarf galaxies, enabling tighter constraints on dark matter annihilation or decay rates.
• By measuring velocity-space substructure in stellar streams, MSE will detect low-mass dark matter subhalos with masses as low as 10^6 M☉, improving subhalo mass function constraints.
• In merging clusters, MSE’s spectroscopy will enable detection of transient offsets and BCG wobbling, with constraints on the self-interaction cross section σ/m ≲ 1 cm²/g achievable through ensemble analysis.
• The combination of high-fidelity redshifts and strong lensing data will allow for sub-kiloparsec-scale mapping of dark matter peaks, reducing uncertainties in halo center estimation below 1–10 kpc.