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Published May 2023 | Published
Journal Article Open

A semi-analytic study of self-interacting dark-matter haloes with baryons


We combine the isothermal Jeans model and the model of adiabatic halo contraction into a semi-analytic procedure for computing the density profile of self-interacting dark-matter (SIDM) haloes with the gravitational influence from the inhabitant galaxies. The model agrees well with cosmological SIDM simulations over the entire core-forming stage up to the onset of gravothermal core-collapse. Using this model, we show that the halo response to baryons is more diverse in SIDM than in CDM and depends sensitively on galaxy size, a desirable feature in the context of the structural diversity of bright dwarfs. The fast speed of the method facilitates analyses that would be challenging for numerical simulations – notably, we quantify the SIDM halo response as functions of the baryonic properties, on a fine mesh grid spanned by the baryon-to-total-mass ratio, M_b/M_(vir), and galaxy compactness, r1/2/Rvir; we show with high statistical precision that for typical Milky-Way-like systems, the SIDM profiles are similar to their CDM counterparts; and we delineate the regime of core-collapse in the Mb/Mvir − r1/2/Rvir space, for a given cross section and concentration. Finally, we compare the isothermal Jeans model with the more sophisticated gravothermal fluid model, and show that the former yields faster core formation and agrees better with cosmological simulations. We attribute the difference to whether the target CDM halo is used as a boundary condition or as the initial condition for the gravothermal evolution, and thus comment on possible improvements of the fluid model. We have made our model publicly available at https://github.com/JiangFangzhou/SIDM.

Additional Information

© 2023 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model). We thank Ethan Nadler, Maya Silverman, Igor Palubski, and Dylan Folsom for helpful general discussions. FJ is partially supported by the Troesh Scholarship from the California Institute of Technology. AB, AHGP, ZCZ, and XD are supported in part by the National Aeronautics and Space Administration (NASA) Astrophysics Theory Program under grant 80NSSC18K1014. ML and OS are supported by the US Department of Energy (DOE) under Award Number DE-SC0007968 and the Binational Science Foundation (grant no. 2018140). DATA AVAILABILITY. The data underlying this article produced by the semi-analytical model are generated using programs available at https://github.com/JiangFangzhou/SIDM. The data of the cosmological simulations are either directly given in the paper or adopted from published works as cited in the paper. The data of the idealized simulations will be available upon reasonable requests.

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August 22, 2023
September 11, 2023