2019/12/31 by Benoit Famaey, Benoît Famaey, Justin Khoury +2
Physics and Astronomy · #Astrophysics #Baryon #Cold dark matter #Cosmology and Gravitation Theories #Dark Matter and Cosmic Phenomena #Dark matter #Galaxies: Formation, Evolution, Phenomena #Galaxy #Galaxy formation and evolution #Galaxy rotation curve #Physics #Surface brightness #astro-ph.CO #astro-ph.GA #gr-qc
paper · pdf · doi:10.1088/1475-7516/2020/06/025
32 pages. v2: Minor edits, references added
arxiv created 2020/01/08 · openalex publication_date 2020/06/12 · arxiv updated 2020/06/17 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
The empirical scaling relations observed in disk galaxies remain challenging for models of galaxy formation. The most striking among these is the Mass Discrepancy-Acceleration Relation (MDAR), which encodes both a tight baryonic Tully-Fisher relation (BTFR) and the observed diversity of galaxy rotation curves through the central surface density relation (CSDR) . Building on our earlier work [1], we propose here that the MDAR is the result of interactions between baryons and `Baryon-Interacting Dark Matter' (BIDM), which heat up the dark matter. Following a bottom-up, hydrodynamical approach, we find that the MDAR follows if: i ) the BIDM equation of state approximates that of an ideal gas; ii ) the BIDM relaxation time is order the Jeans time; iii ) the heating rate is inversely proportional to the BIDM density. Remarkably, under these assumptions the set of hydrodynamical equations together with Poisson's equation enjoy an anisotropic scaling symmetry. In the BIDM-dominated regime, this gives rise to an enhanced symmetry which fully captures the low-acceleration limit of the MDAR . We then show that, assuming a cored pseudo-isothermal profile at equilibrium, this set of equations gives rise to parameters reproducing the MDAR . Specifically, in the flat part of the rotation curve the asymptotic rotational velocity matches the parametric dependence of the BTFR . Moreover, in the central region of high-surface brightness galaxies, the profile reproduces the CSDR . Finally, by studying the time-dependent approach to equilibrium, we derive a global combination of the BTFR and CSDR, which matches the expectations in low surface-brightness galaxies. The form of the heating rate also makes model-independent predictions for various cosmological observables. We argue that our scenario satisfies existing observational constraints, and, intriguingly, offers a possible explanation to the EDGES anomaly.