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Gusts in the Headwind: Uncertainties in Direct Dark Matter Detection

Lawrence, Grace E. and Duffy, Alan R. and Blake, Chris A. and Hopkins, Philip F. (2022) Gusts in the Headwind: Uncertainties in Direct Dark Matter Detection. . (Unpublished)

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We use high-resolution, hydrodynamic, galaxy simulations from the Latte suite of FIRE-2 simulations to investigate the inherent variation of dark matter in sub-sampled regions around the Solar Circle of a Milky Way-type analogue galaxy and its impact on direct dark matter detection. These simulations show that the baryonic backreaction, as well as the assembly history of substructures, has lasting impacts on the dark matter's spatial and velocity distributions. These are experienced as 'gusts' of dark matter wind around the Solar Circle, potentially complicating interpretations of direct detection experiments on Earth. We find that the velocity distribution function in the galactocentric frame shows strong deviations from the Maxwell Boltzmann form typically assumed in the fiducial Standard Halo Model, indicating the presence of high-velocity substructures. By introducing a new numerical integration technique which removes any dependencies on the Standard Halo Model, we generate event-rate predictions for both single-element Germanium and compound Sodium Iodide detectors, and explore how the variability of dark matter around the Solar Circle influences annual modulation signal predictions. We find that these velocity substructures contribute additional astrophysical uncertainty to the interpretation of event rates, although their impact on summary statistics such as the peak day of annual modulation is generally low.

Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription Paper ItemDark Mark python package
Hopkins, Philip F.0000-0003-3729-1684
Additional Information:The author G.E.L. gratefully acknowledges Darren Croton for his guidance and feedback on our manuscript and Ciaran O’Hare for valuable scientific discussions and insights during this work. G.E.L. would like to acknowledge support through an Australian Government Research Training Program Scholarship. This research was supported by the Australian Research Council Centre of Excellence for Dark Matter Particle Physics (CDM; project number CE200100008). Parts of this research were supported by the Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D; project number CE170100013). Figures in this work were created using Matplotlib (Hunter 2007) and made use of colormaps from the CMasher package (van der Velden 2020). DATA AVAILABILITY. The author acknowledges the use of the FIRE-2 simulations, specifically the Latte suite. The full simulation halo snapshot for the m12f halo used in this work is publicly available via yt Hub at The Dark Mark python package created for this work is publicly available at The secondary data underlying this article will be shared on reasonable request to the corresponding author.
Group:Astronomy Department, TAPIR
Funding AgencyGrant Number
Australian Government Research Training Program ScholarshipUNSPECIFIED
Australian Research CouncilCE200100008
Australian Research CouncilCE170100013
Subject Keywords:(cosmology:) dark matter – astroparticle physics – hydrodynamics – scattering – Galaxy:general – software: simulations
Record Number:CaltechAUTHORS:20220816-222004923
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:116330
Deposited By: George Porter
Deposited On:18 Aug 2022 22:36
Last Modified:18 Aug 2022 22:36

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