Probing the radial acceleration relation and the strong equivalence principle with the Coma cluster ultra-diffuse galaxies

Freundlich, J.; Famaey, B.; Oria, P. -A.; Bílek, M.; Müller, O.; Ibata, R.

doi:10.48550/arxiv.2109.04487

Cited by 3 publications

(4 citation statements)

References 154 publications

(284 reference statements)

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“…We note that the rotation curve with EFE is very well fit by the formula proposed by Freundlich et al (2021), approximating the average radial acceleration g r (r) over a sphere at a given radius r in a constant external field :…”

Section: Ngc 5055: An Archetypical Galaxy Under a Strong Efementioning

confidence: 65%

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The phantom dark matter halos of the Local Volume in the context of modified Newtonian dynamics

Oria,

Famaey,

Thomas

et al. 2021

Preprint

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We explore the predictions of Milgromian gravity (MOND) in the Local Universe by considering the distribution of the 'phantom' dark matter (PDM) that would source the MOND gravitational field in Newtonian gravity, allowing an easy comparison with the dark matter framework. For this, we specifically deal with the quasi-linear version of MOND (QUMOND). We compute the 'stellar-to-(phantom)halo-mass relation' (SHMR), a monotonically increasing power-law resembling the SHMR observationally deduced from spiral galaxy rotation curves in the Newtonian context. We show that the gas-to-(phantom)halo-mass relation is flat. We generate a map of the Local Volume in QUMOND, highlighting the important influence of distant galaxy clusters, in particular Virgo. This allows us to explore the scatter of the SHMR and the average density of PDM around galaxies in the Local Volume, Ω pdm ≈ 0.1, below the average cold dark matter density in a ΛCDM Universe. We provide a model of the Milky Way in its external field in the MOND context, which we compare to an observational estimate of the escape velocity curve. Finally, we highlight the peculiar features related to the external field effect in the form of negative PDM density zones in the outskirts of each galaxy, and test a new analytic formula for computing galaxy rotation curves in the presence of an external field in QUMOND. While we show that the negative PDM density zones would be difficult to detect dynamically, we quantify the weak lensing signal they could produce for lenses at z ∼ 0.3.

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Section: Ngc 5055: An Archetypical Galaxy Under a Strong Efementioning

confidence: 65%

“…Dynamically, the best we can probably hope to achieve is the Keplerian decline of the rotation curve associated to the EFE. With this in mind, we will now study in detail a new formula proposed in Freundlich et al (2021) and compare it to our exact QUMOND calculations.…”

Section: Ngc 5055: An Archetypical Galaxy Under a Strong Efementioning

confidence: 99%

The phantom dark matter halos of the Local Volume in the context of modified Newtonian dynamics

Oria,

Famaey,

Thomas

et al. 2021

Preprint

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“…Preliminary results suggest a significant problem for ΛCDM because the dwarfs should be immune to tides, but this issue seems to be resolved in MOND where they would be much more eas-ily disrupted. 1 A similar analysis might also be possible in the Coma cluster (Chilingarian et al 2019;Freundlich et al 2021).…”

Section: Tidal Stabilitymentioning

confidence: 84%

From galactic bars to the Hubble tension: weighing up the astrophysical evidence for Milgromian gravity

Banik,

Zhao

2021

Preprint

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Astronomical observations reveal a major deficiency in our understanding of physics − the detectable mass is insufficient to explain the observed motions in a huge variety of systems given our current understanding of gravity, Einstein's General theory of Relativity (GR). This missing gravity problem may indicate a breakdown of GR at low accelerations, as posited by Milgromian dynamics (MOND). We review the MOND theory and its consequences, including in a cosmological context where we advocate a hybrid approach involving light sterile neutrinos to address MOND's cluster-scale issues. We then test the novel predictions of MOND using evidence from galaxies, galaxy groups, galaxy clusters, and the large scale structure of the Universe. We also consider whether the standard cosmological paradigm (ΛCDM) can explain the observations, and review several previously published highly significant falsifications of it. Our overall assessment considers both the extent to which the data agree with each theory and how much flexibility each has when accommodating the data, with the gold standard being a clear a priori prediction not informed by the data in question. We also consider some future tests, including on scales much smaller than galaxies. Our conclusion is that MOND is favoured by a wealth of data across a huge range of astrophysical scales, ranging from the kpc scales of galactic bars to the Gpc scale of the local supervoid and the Hubble tension, which is alleviated in MOND through enhanced cosmic variance.

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“…They have pointed out that these deduced fields are correlated with the large-scale cosmic environments of galaxies, supporting the EFE interpretation of the SPARC data. On the other hand, Freundlich et al (2021) have not found indications of EFE from an analyses of 11 UDGs including those in the Coma cluster (a fact that could, however, be due to their being heated tidally in the cluster), while study of tidally-affected dwarfs in the Fornax cluster found, to the contrary, strong indication that they are subject to the EFE of the cluster (E. Asencio, private communication).…”

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confidence: 99%

Numerical Solutions of the External Field Effect on the Radial Acceleration in Disk Galaxies

Chae,

Milgrom

2022

Preprint

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In MOND(modified Newtonian dynamics)-based theories the strong equivalence principle (SEP) is generically broken in an idiosyncratic manner, manifested in the action of an "external field effect (EFE)". The internal dynamics in a self-gravitating system is affected even by a constant external field in which the system is freely falling. In disk galaxies the EFE due to the cosmic large-scale structure can induce warps and modify the rotational speeds. Due to the non-linearity of MOND, it is difficult to derive analytic expressions of this important effect, especially since a disk in an inclined external field defines a three-dimensional geometry. Here we study the EFE numerically using a Miyamoto-Nagai model of disk galaxies, in two non-relativistic Lagrangian theories of MOND: the 'Aquadratic-Lagrangian' theory (AQUAL) and 'Quasilinear MOND' (QUMOND). We investigate particularly to what degree an external field modifies the quasi-flat part of rotation curves in disk systems. While our QUMOND results agree well with published numerical results in QUMOND, we find that AQUAL predicts weaker EFE than published AQUAL results. However, AQUAL still predicts stronger EFE than QUMOND, which demonstrates current theoretical uncertainties. We also illustrate how the MOND prediction on the rising part of the rotation curve, in the inner parts, depends largely on disk thickness but only weakly on a plausible external field for a fixed galaxy model. Finally, we summarize our results for the outer parts as an improved, approximate analytic expression. The results for the outer and inner parts will be useful for interpreting observed rotation curves.

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Probing the radial acceleration relation and the strong equivalence principle with the Coma cluster ultra-diffuse galaxies

Cited by 3 publications

References 154 publications

The phantom dark matter halos of the Local Volume in the context of modified Newtonian dynamics

The phantom dark matter halos of the Local Volume in the context of modified Newtonian dynamics

From galactic bars to the Hubble tension: weighing up the astrophysical evidence for Milgromian gravity

Numerical Solutions of the External Field Effect on the Radial Acceleration in Disk Galaxies

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