Enticing, but with issues. Lots of self-citation, an arXiv review delay, very short, the author is primarily a mathematician and not primarily an astronomer, although his does have an institutional affiliation to a legitimate cosmology research center.
Gas-rich ultra-diffuse galaxies (UDGs) are an unusually sharp test for gravity models tied to the baryonic Tully--Fisher relation because several systems appear to rotate too slowly for their baryonic masses. This study revisits the six isolated gas-rich UDGs analysed by Mancera Piña et al. with the current outer-radius prescription of hyperconical modified gravity (HMG), using the published baryonic masses and circular velocities at the outer radii. The scan over the neighbourhood-scale parameter drives the model towards the asymptotic branch of HMG. For that limit, the HMG velocities are still systematically high for four of the six galaxies. Relative to the observed values, the fixed asymptotic branch gives χ2≃18.1 for six objects, whereas Newtonian baryons alone give χ2≃9.7, but MOND interpolation is much worse (χ2≃615.7). Using combined uncertainties, the per-galaxy HMG tension ranges from 0.2σ to 2.1σ, very similar to the 0.1σ to 1.7σ found for Newtonian baryons, and much smaller than the 3.7σ to 5.9σ obtained for MOND. We conclude that the present outer-radius HMG implementation alleviates the difficulties of MOND, but is still not sufficient to account for the published central values of the UDG sample. Gas-rich UDGs therefore provide a useful discriminant between MOND and HMG.
Robert Monjo, "Gas-rich ultra-diffuse galaxies: alleviating the MOND tension with HMG" arXiv:2604.09652 (March 30, 2026) (4 pages, 1 figure).
More credible. An established MOND astrophysicist. A big blow to MOND critics.
It is a common miss-conception that 1E 0657-56, the "Bullet Cluster", is somehow inconsistent with MOND expectations. The argument centres on the fact that the baryonic matter distribution of this system is dominated by the X-ray emitting gas, while the total projected surface density required under General Relativity to explain the observed lensing signal, centres on the observed galaxies. This is sometimes interpreted as being in conflict with MOND, as under such an interpretation, it is naively assumed that all dark matter being absent, the gravitational potential should necessarily be dominated by the largest mass distribution, that of the gas.
However, just as under General Relativity, under MOND, the total gravitational potential of a system depends sensitively upon the volume density and not just on the total mass. It is shown in this letter that the surface density which QUMOND predicts will be inferred under a standard gravity framework from the total gravitational potential of the Bullet Cluster, closely matches what General Relativity inferences of lensing observations return. The close-to-point-like galaxies imply under QUMOND a relatively much larger surface density signal than what is expected from the Mpc scale gas distribution.
Strong but straight claims from Xavier. The former is the most cryptic work on MOND I've seen so far.
ReplyDeleteRevisiting the missing mass problem in MOND for nearby galaxy clusters
ReplyDeleteDong Zhang1,*, Akram Hasani Zonoozi1,2, and Pavel Kroupa1,3,†
Phys. Rev. D 113, 043027 – Published 17 February, 2026
DOI: https://doi.org/10.1103/mp3f-q5dc
Abstract
In the framework of Milgromian dynamics (MOND), galaxy clusters have been thought to have about a factor of two less baryonic mass than gravitational mass. One hypothesized source of this missing mass is undetected baryons. Extensive observations and studies indicate that the baryon content of galaxy clusters is primarily composed of the intracluster medium (ICM). In this work we reevaluate the overall stellar mass in galaxy clusters taking into account recent work on the galaxy-wide stellar initial mass function of stars (gwIMF) needed to synthesise the metals observed in galaxies. Given their supersolar metallicities and short formation timescales, massive elliptical galaxies are inferred to have formed with highly top-heavy gwIMFs, which in turn leave behind a substantial mass in stellar remnants. The dependency of the gwIMF on the properties and evolution of a galaxy is well encapsulated by the integrated galaxy-wide initial mass function (IGIMF) theory, developed independently of MOND. We utilize observational data at redshifts z<0.1
from the Wide-field Nearby Galaxy-cluster Survey (WINGS) and the Two Micron All Sky Survey (2MASS). Masses of galaxies and intracluster light (ICL) are calculated for 46 galaxy clusters using the IGIMF theory. The resulting masses in stars and in remnants are combined with previously derived ICM masses to estimate the total baryonic masses of the clusters. These baryonic masses are then compared to the MOND dynamical masses of the clusters, which are derived from hydrostatic equilibrium of the ICM based on earlier studies. As a complement, we include a comparison with several weak/strong lensing masses in the MOND framework. Our results show that the stellar masses of galaxies and the ICL increase substantially when applying the galaxy-wide mass-to-light ratios derived from the IGIMF theory. This leads to a significant rise in the estimated baryonic masses of galaxy clusters. In the sample of 46 galaxy clusters, the baryonic component on average accounts for 52+4
−3%
of the MOND dynamical mass when considering only the ICM contribution. The baryonic mass in stars, remnants and the ICM accounts for at least 88+5+2
−4−1%
of the MOND dynamical mass. The contribution by stellar remnants that arises from nucleosynthesis constraints thus significantly alleviates the missing mass problem in MOND. Finally, we briefly discuss the compatibility of the IGIMF framework with the radial acceleration relation (RAR), and studies of MOND weak/strong lensing and related issues. A more comprehensive investigation will require future work that combines the IGIMF with self-consistent, spatially resolved formation, evolution, and resulting mass distribution models of galaxies.
@neo Good catch.
ReplyDeleteif true only 12% need to be accounted perhaps neutrino or PBH
ReplyDeleteA much more manageable percentage with plausible mechanisms.
ReplyDeletethe paper gets the mass estimate from big bang nucleosynthesis, rather than direct observation of stellar remnants. in some ways this is like saying the missing baryon problem, where there is a factor of 2 total mass of baryons unaccounted for, is stellar remnants, which would close the mass gap for MOND in galaxy clusters. in other words, if the missing baryon problem consists of unseen stellar remnants in galaxy clusters that would greatly reduce the MOND galaxy cluster problem, since it is under counting the mass.
ReplyDelete