Constraining the shape of dark matter haloes using only starlight
- 1Instituto de Astrofísica de Canarias, La Laguna
- 2CeBio y Departamento de Ciencias Básicas, Universidad Nacional del Noroeste de la Prov. de Buenos Aires, UNNOBA, CONICET
- 3Department of Astronomy, University of Virginia
Abstract
Under the collisionless cold dark matter (CDM) paradigm, galaxies with stellar masses below 105–6M⊙ 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.
Related
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- Constraints on Dark Matter Annihilation from Starlight-Induced Inverse Compton Emission in Omega Centauri
- Dynamical friction vs. subhalo heating in Cold Dark Matter haloes
- Scatter, bias, and chaos of satellite orbits in triaxial dark matter haloes
- The connection between massive galaxies and their dark matter haloes from z = 0.25 to z ∼ 4 from the combined COSMOS, XMM-LSS and ECDF-S fields
BibTeX
@article{jorge2026constraining,
title = {{Constraining the shape of dark matter haloes using only starlight}},
author = {Sánchez Almeida Jorge and Plastino Angel R. and Guerra Arencibia Sergio and Kallivayalil Nitya and Warfield Jack T.},
journal = {Astronomy \& Astrophysics},
year = {2026},
month = oct,
doi = {10.1051/0004-6361/202661281},
url = {https://doi.org/10.1051/0004-6361/202661281},
note = {CC BY},
}
RIS
TY - JOUR
TI - Constraining the shape of dark matter haloes using only starlight
AU - Sánchez Almeida Jorge
AU - Plastino Angel R.
AU - Guerra Arencibia Sergio
AU - Kallivayalil Nitya
AU - Warfield Jack T.
PY - 2026
DA - 2026/10/23
JO - Astronomy & Astrophysics
DO - 10.1051/0004-6361/202661281
UR - https://doi.org/10.1051/0004-6361/202661281
AB - Under the collisionless cold dark matter (CDM) paradigm, galaxies with stellar masses below 105–6M⊙ 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.
SN - 0004-6361
SN - 1432-0746
ER -