I'm highly skeptical of a study that purports to contradict decades of previous observational data whose results had a broad consensus in the field of galaxy dynamics (and which was the main motivator for dark matter particle models such as self-interacting dark matter, warm dark matter, and axion-like particle/fuzzy/ultralight dark matter), with a small "curated" sample.
I also question comparing this small curated sample mostly to cold dark matter simulations which themselves are often devised to fit the data rather than having a rigorous physics basis.
This comes across as cherry picking rather than as the robust observational constraint that the paper claims to be seeking to develop, particularly where there doesn't seem to be a lot of attention given to the uncertainties in their observational data points.
There seem to be a lot of observation points outside the CDM range in Figure 4 below, and Figure 5 represents only comparisons with simulations, which again, aren't very rigorous reproductions of pure physics and have a strong phenomenological matching component.
Also, while this paper purports to quantify how much energy from stellar feedback is necessary to produce the observed results (which is a worthwhile and important thing to do), its analysis of whether that amount is actually plausible and has a strong physics justification is lacking.
But I'm blogging this paper anyway. That's because I don't want to ignore papers just because they might disagree with my preconceived notions. It is better to engaged and struggle with scholarship that you doubt, and to change your mind if it is sufficiently convincing.
The images below are the ones described in the arXiv comment from the authors as containing the "main results."
Two of the most prominent small-scale challenges to the cold dark matter (CDM) paradigm are the cusp-core and diversity-of-rotation-curves problems. The former concerns the shallow inner DM density profiles inferred for many galaxies compared with the cusps predicted by collisionless CDM, while the latter concerns the wider range of inner DM densities and rotation curve shapes inferred observationally than hydrodynamical simulations traditionally reproduce. Robust observational constraints on DM core sizes and halo densities are therefore essential for testing both the nature of DM and the impact of galaxy formation processes.
We analyse the inner DM distribution of a curated sample of 48 gas-rich galaxies and 8 Milky Way gas-poor satellites, spanning 6 orders of magnitude in M∗. We find substantial scatter in DM core sizes and degrees of coreness, with both cuspy and cored haloes occurring over a broad M∗ range. The cores are energetically consistent with stellar feedback, requiring modest supernova energy coupling efficiencies of order 0.1−1%. Comparisons with the NIHAO, FIRE-2, and EDGE simulations reveal broad agreement in the inner DM densities and logarithmic slopes of observed and simulated galaxies.
The main residual differences concern the steep slopes of some massive simulated galaxies and differences in SHMRs. Using a rotation-curve diversity diagnostic from previous work, we find that extreme discrepancies with simulations are absent from our curated sample and largely attributable to uncertain kinematics or baryonic mass distributions. Within the scope of our analysis, we find no evidence of a systematic inner-density tension between our galaxy sample and current ΛCDM hydrodynamical simulations. Together with the modest energetic requirements for core formation, this substantially alleviates the cusp-core and diversity-of-rotation-curves problems.
Pavel E. Mancera Piña, Justin I. Read, Jorge Sarrato-Alós, Claudia Muni, "Dark matter haloes from dwarf to massive galaxies: no systematic inner-density tension with ΛCDM hydrodynamical simulations" arXiv:2609.25220 (September 21, 2026) (Accepted for publication in A&A).
No comments:
Post a Comment