Warm dark matter constraints using Milky Way satellite observations and subhalo evolution modeling

Abstract

Warm dark matter (WDM) can potentially explain small-scale observations that currently challenge the cold dark matter (CDM) model, as warm particles suppress structure formation due to free-streaming effects. Observing small-scale matter distribution provides a valuable way to distinguish between CDM and WDM. In this work, we use observations from the Dark Energy Survey and PanSTARRS1, which observe 270 Milky-Way satellites after completeness corrections. We test WDM models by comparing the number of satellites in the Milky Way with predictions derived from the Semi-Analytical SubHalo Inference Modeling (SASHIMI) code, which we develop based on the extended Press-Schechter formalism and subhalos' tidal evolution prescription. We robustly rule out WDM with masses lighter than 4.4 keV at 95% confidence level for the Milky-Way halo mass of 10 12 M ⊙ . The limits are a weak function of the (yet uncertain) Milky-Way halo mass, and vary as m WDM ≳ 3.6-5.1 keV for ð0.6-2.0Þ × 10 12 M ⊙ . For the sterile neutrinos that form a subclass of WDM, we obtain the constraints of m ν s > 12 keV for the Milky-Way halo mass of 10 12 M ⊙ , independent of the mixing angle. These results based on SASHIMI do not rely on any assumptions of galaxy formation physics or are not limited by numerical resolution. The models, therefore, offer a robust and fast way to constrain the WDM models. By applying a satellite forming condition, however, we can rule out the WDM mass lighter than 9.0 keV for the Milky-Way halo mass of 10 12 M ⊙ .

Anticipating the XRISM search for the decay of resonantly produced sterile neutrino dark matter

“…Different assumptions in these areas can lead to dramatic differences in the number of predicted satellites: the compilation by Kim et al (2018) reports 120-150 satellites, the analysis by Newton et al (2018) expects ∼ 120 satellites, and Nadler et al (2020) instead predicts of order 220. These results are key inputs for further studies of both WDM generally (Enzi et al 2021;Nadler et al 2021;Newton et al 2021) and 1 (Dekker et al 2022;Zelko et al 2022). In such studies, the satellite counts typically generate the strongest constraints of any observation: hm < 8.5 × 10 8 M ⊙ (5 M. L.) for Enzi et al (2021) and hm < 2.5 × 10 7 M ⊙ (5 M. L.) for Nadler et al (2021).…”

Warm dark matter from a gravitational freeze-in in extra dimensions

“…Typically masses larger than a few keV are required to avoid conflict with the data, see e.g. [44][45][46][47]. In the following, we take the limit m WDM ≥ 3.5 keV [44] which is based on an analysis of Lyman-α forest observations.…”

Constraints on dark matter-neutrino scattering from the Milky-Way satellites and subhalo modeling for dark acoustic oscillations

“…1 To quickly derive theoretical prediction of the number of Milky-Way satellites, we study and use a modified version of a semi-analytical subhalo model based on the extended Press-Schechter (EPS) formalism [74][75][76][77] and subhalos' tidal evolution prescription, as developed in refs. [78,79]. The primordial density fluctuations collapse gravitationally, forming DM halos.…”

“…The model developed in refs. [78,79] describes the complementary semianalytical evolution of a host halo and subhalos, including tidal stripping, with analytical expressions for the hierarchical assembly of DM halos provided by the EPS formalism. In this study, we extend it to interacting dark matter models by modifying the EPS formalism, in particular the window function and the critical overdensity.…”