Constraining the shape of dark matter haloes using only starlight
Year: 2026
Type: article
Abstract: Under the collisionless cold dark matter (CDM) paradigm, galaxies with stellar masses below 10 5–6 M ⊙ are expected to preserve primordial cuspy dark matter (DM) profiles. Because baryonic feedback should be too weak to transform cusps into cores at these masses, such galaxies provide especially sensitive tests of DM physics. If cores are observed in these systems, they could indicate departures from the CDM paradigm. To address this problem, Paper I of our series introduced the Eddington inversion method tool (EIM tool), a photometry-based diagnostic that avoids the need for long-term spectroscopic observations and is suitable for the analysis of the forthcoming large photometric surveys of galaxies. The method relies on the fact that embedding a stellar distribution with a central core inside a cuspy Navarro-Frenk-White (NFW) halo can require a negative phase-space distribution function f , which is physically impossible. By fitting observed stellar surface densities using f as a free parameter, the EIM tool tests whether an assumed gravitational potential is physically consistent with an observed stellar distribution. This paper validates EIM tool using globular clusters, dwarf spheroidal galaxies (dSphs), and numerical simulations with independently known potentials. We applied the method to 21 globular clusters, and it rejected NFW cusps in 71% of cases while consistently favoring cored Schuster–Plummer models, accurately recovering expected core radii. When applied to dSphs, EIM tool reproduced conclusions from classical dynamical studies: Sculptor and Fornax favored cored halos, whereas Draco remained compatible with a cusp. Tests on EDGE and FIRE simulations further showed that the tool reliably rejects cuspy NFW profiles when the true DM distribution is core-like. Overall, these results establish EIM tool as a robust and efficient photometric method for distinguishing cored and cuspy DM halos.
Source: Astronomy and Astrophysics
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,865
Awards: G1175115578, G121809054, G1622782223, G1855990336, G210041235, G2262748287, G2309174360, G2601397997, G2660406951, G279363373, Unravelling the Dark Universe from the Canary Islands Observatories, G300979063, G34346518, G3480869486, G3518538256, G3681454997, G3874880780, G4042783231, G410571670, G425668148, G430777504, G4442677895, G451917667, G4526231891, G5080475149, G5151686405, G5195188938, G5421974903, G5539308778, G5967599077, G7084143925, G8909612584, G8920660035, G897484643, G929308097, G99296377
OpenAlex ID: W7171777209