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

Genina, A. and Read, J.I. and Frenk, C.S. and Cole, S. and Benítez-Llambay, A. and Ludlow, A.D. and Navarro, J.F. and Oman, K.A. and 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). pp. 144-163.


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.

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Publisher statement:This article has been accepted for publication in Monthly notices of the Royal Astronomical Society. ©: 2020 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Date accepted:03 August 2020
Date deposited:18 September 2020
Date of first online publication:14 August 2020
Date first made open access:18 September 2020

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