The ΛCDM model is contradicted by a host of independent observational tests (dozens of them).
The luminosity-temperature relation for galaxy clusters is independent of any of these previous tests and doesn't share significant sources of systemic error with it. And, the ΛCDM, again, is not a good fit to this data, while one of the more well-studied modified gravity theories, f(R) gravity, does significantly better.
We investigate the luminosity-temperature (L-T) relation of galaxy clusters as a probe for testing modified gravity (MG) theories, focusing on f(R) gravity and symmetron models. Using an improved semi-analytic framework that incorporates angular momentum acquisition, dynamical friction, and shock heating within the modified punctuated equilibrium model, we compare predictions against hydrodynamical simulations and observational data.
While massive clusters remain largely screened and follow standard ΛCDM predictions, low-mass systems (kT ≲ 1−2 keV) exhibit systematic deviations characterized by steeper L-T slopes in MG scenarios.
Crucially, we demonstrate that these signatures cannot be mimicked by conventional astrophysical processes such as feedback or angular momentum effects, which primarily affect normalization rather than curvature. Our results establish the L-T relation as a robust diagnostic tool for distinguishing general relativity from screened MG theories, with the strongest discriminatory power emerging at group scales accessible to current and future X-ray surveys. Moreover, a normalized reduced χ2 analysis of the L-T relation shows that MG models provide significantly better agreement with observational data than ΛCDM, with several realizations achieving excellent fits while the ΛCDM model consistently performs worst.
Antonino Del Popolo, Saeed Fakhry, David F. Mota, "Luminosity-Temperature Relation as a Probe for Modified Gravity" arXiv:2603.15077 (March 16, 2026).
See also this paper, which finds fault with the NFW halo distribution which is mathematically implied in any collisionless dark matter particle model, yet clearly time and again, does not reflect real world observations.
We investigate how reliably the global properties of Milky Way-mass dark matter haloes can be recovered from dynamical data over a limited radial range, particularly ≲30 kpc where observations are most sensitive but baryonic processes modify the halo structure.
Using the ARTEMIS simulations, which produce varying degrees of baryon-induced contraction, we fit dark matter profiles over restricted radial ranges using commonly adopted parametric models. Assuming negligible observational uncertainties allows the systematic errors from these choices to be isolated.
When fits are confined to inner radii, an NFW profile underestimates the virial mass by a factor of ≈2 on average (≈4 for some systems), and the concentration by a factor of ≈2. Einasto and generalised-NFW models provide excellent local fits but retain similar global biases.
In contrast, the contracted halo prescription from Cautun et al. (2020) yields stable extrapolations and recovers unbiased halo mass estimates over all radii.
The inferred mass improves systematically with increasing radial coverage, and tracers beyond ≳50 kpc largely eliminate the mean bias for all models. The local dark matter density at the Solar radius is recovered to within ≲5% for all profiles other than NFW. These biases are sufficient to reconcile recent low Milky Way mass estimates derived from inner rotation-curve analyses with the canonical ≈ 10^12 M⊙.
We additionally find a halo-to-halo scatter of ≳0.1 dex (≈25%) persists even under idealised conditions, setting a likely lower limit for the precision of halo mass estimates.
Diego Dado, Shaun T. Brown, Azadeh Fattahi, Andreea S. Font, Ian G. McCarthy, "Implications of a contracted dark matter halo for the Milky Way's inferred virial mass" arXiv:2603.13516 (March 13, 2026) (submitted to MNRAS).
Some analysis of the measurement issues for galactic rotation curve of the Milky Way are discussed here.
No comments:
Post a Comment