To β or not to β: can higher-order Jeans analysis break the mass–anisotropy degeneracy in simulated dwarfs?

Genina, A.; Read, J.I.; Frenk, C.S.; Cole, S.; Benítez-Llambay, A.; Ludlow, A.D.; Navarro, J.F.; Oman, K.A.; Robertson, A.

Abstract

We test a non-parametric higher-order Jeans analysis method, GRAVSPHERE, on 32 simulated dwarf galaxies comparable to classical Local Group dwarfs like Fornax. The galaxies are selected from the APOSTLE suite of cosmological hydrodynamics simulations with Cold Dark Matter (CDM) and Self-Interacting Dark Matter (SIDM) models, allowing us to investigate cusps and cores in density distributions. We find that, for CDM dwarfs, the recovered enclosed mass profiles have a bias of no more than 10 per cent, with a 50 per cent scatter in the inner regions and a 20 per cent scatter near the half-light radius, consistent with standard mass estimators. The density profiles are also recovered with a bias of no more than 10 per cent and a scatter of 30 per cent in the inner regions. For SIDM dwarfs, the mass and density profiles are recovered within our 95 per cent confidence intervals, but are biased towards cuspy dark matter distributions. This is mainly due to a lack of sufficient constraints from the data. We explore the sources of scatter in the accuracy of the recovered profiles and suggest a χ2 statistic to separate successful models from biased ones. Finally, we show that the uncertainties on the mass profiles obtained with GRAVSPHERE are smaller than those for comparable Jeans methods, and that they can be further improved if stronger priors, motivated by cosmological simulations, are placed on the velocity anisotropy. We conclude that GRAVSPHERE is a promising Jeans-based approach for modelling dark matter distributions in dwarf galaxies.

Citation

Genina, A., Read, J., Frenk, C., Cole, S., Benítez-Llambay, A., Ludlow, A., Navarro, J., Oman, K., & Robertson, A. (2020). To β or not to β: can higher-order Jeans analysis break the mass–anisotropy degeneracy in simulated dwarfs?. Monthly Notices of the Royal Astronomical Society, 498(1), 144-163. https://doi.org/10.1093/mnras/staa2352

• Journal Article Type: Article
• Acceptance Date: Aug 3, 2020
• Online Publication Date: Aug 14, 2020
• Publication Date: 2020-10
• Deposit Date: Aug 18, 2020
• Publicly Available Date: Sep 18, 2020
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Royal Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 498
• Issue: 1
• Pages: 144-163
• DOI: https://doi.org/10.1093/mnras/staa2352
• Public URL: https://durham-repository.worktribe.com/output/1258306