Abstract
Galactic rotation curves exhibit diverse behavior in the inner regions while obeying an organizing principle; i.e., they can be approximately described by a radial acceleration relation or the modified Newtonian dynamics phenomenology. We analyze the rotation curve data from the SPARC sample and explicitly demonstrate that both the diversity and uniformity are naturally reproduced in a hierarchical structure formation model with the addition of dark matter self-interactions. The required concentrations of the dark matter halos are fully consistent with the concentration-mass relation predicted by the Planck cosmological model. The inferred stellar mass-to-light () ratios scatter around , as expected from population synthesis models, leading to a tight radial acceleration relation and a baryonic Tully-Fisher relation. The inferred stellar-halo mass relation is consistent with the expectations from abundance matching. These results provide compelling arguments in favor of the idea that the inner halos of galaxies are thermalized due to dark matter self-interactions.
- Received 23 October 2018
- Revised 25 April 2019
DOI:https://doi.org/10.1103/PhysRevX.9.031020
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Popular Summary
Stars and gas in spiral galaxies rotate around the galactic center. A graph of rotation speeds versus distances from the center, called a rotation curve, allows astronomers to infer the presence of dark matter. The rotation curves of galaxies show a wide diversity of shapes but also exhibit an organizing principle: The centripetal acceleration is tightly correlated with the gravitational force exerted by luminous matter, leading to a puzzling uniformity that is seemingly at odds with the presence of dark matter in these galaxies. These features of rotation curves have puzzled astronomers and physicists for over three decades. We show that if the dark matter halo is thermalized in the central regions of the galaxies where stars rotate, then both the diversity and uniformity of the rotation curves are naturally reconciled.
We take the rotation-curve data of 135 galaxies, the largest uniform sample of its kind, and analyze them using the self-interacting dark matter model. This model assumes that the dark matter particles have strong self-interactions, analogous to the nucleons. Dark matter self-interactions thermalize the inner halo and tie together the distributions of dark matter and luminous matter (stars and gas). The model fits all rotation curves and explains their uniformity while being consistent with large-scale structure data.
Our results indicate that dark matter, which comprises about 85% of the mass in the Universe, has more complex features than envisaged in the prevailing cold dark matter theory.
