The distribution of relative proper motions of wide binaries in <i>Gaia</i> DR2: MOND or multiplicity?

Clarke, C. J.

doi:10.1093/mnrasl/slz161

Cited by 26 publications

(16 citation statements)

References 13 publications

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“…Recently, Pittordis & Sutherland (2019) showed that MOND without an EFE is completely ruled out by the observed relative velocity distribution of wide binary stars in the Solar neighbourhood at separations of ≈ 10 kAU. Including the EFE leads to nearly Newtonian behaviour, though the predicted 20% difference is likely detectable in a more thorough analysis (Banik & Zhao 2018c) that must include contamination by undetected close companions (Clarke 2020).…”

Section: Milgrommentioning

confidence: 99%

The KBC void and Hubble tension contradict $Λ$CDM on a Gpc scale $-$ Milgromian dynamics as a possible solution

Haslbauer,

Banik,

Kroupa

2020

Preprint

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The KBC void is a local underdensity with the observed relative density contrast δ ≡ 1 − ρ/ρ 0 = 0.46 ± 0.06 between 40 and 300 Mpc around the Local Group. If mass is conserved in the Universe, such a void could explain the 5.3σ Hubble tension. However, the MXXL simulation shows that the KBC void causes 6.04σ tension with standard cosmology (ΛCDM). Combined with the Hubble tension, ΛCDM is ruled out at 7.09σ confidence. Consequently, the density and velocity distribution on Gpc scales suggest a long-range modification to gravity. In this context, we consider a cosmological MOND model supplemented with 11 eV/c 2 sterile neutrinos. We explain why this νHDM model has a nearly standard expansion history, primordial abundances of light elements, and cosmic microwave background (CMB) anisotropies. In MOND, structure growth is self-regulated by external fields from surrounding structures. We constrain our model parameters with the KBC void density profile, the local Hubble and deceleration parameters derived jointly from supernovae at redshifts 0.023 − 0.15, time delays in strong lensing systems, and the Local Group velocity relative to the CMB. Our best-fitting model simultaneously explains these observables at the 1.14% confidence level (2.53σ tension) if the void is embedded in a time-independent external field of 0.055 a 0 . Thus, we show for the first time that the KBC void can naturally resolve the Hubble tension in Milgromian dynamics. Given the many successful a priori MOND predictions on galaxy scales that are difficult to reconcile with ΛCDM, Milgromian dynamics supplemented by 11 eV/c 2 sterile neutrinos may provide a more holistic explanation for astronomical observations across all scales.

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Section: Milgrommentioning

confidence: 99%

The KBC void and Hubble tension contradict $Λ$CDM on a Gpc scale $-$ Milgromian dynamics as a possible solution

Haslbauer,

Banik,

Kroupa

2020

Preprint

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“…The more subtle effect with the EFE is still allowed observationally, and should be testable with future data releases and/or further analysis. The main source of contamination is probably hierarchical triples, which should be accounted for statistically (Belokurov et al 2020;Clarke 2020).…”

Section: Introductionmentioning

confidence: 99%

The Global Stability of M33 in MOND

Banik

Thies

Famaey

et al. 2020

ApJ

118

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The dynamical stability of disk galaxies is sensitive to whether their anomalous rotation curves are caused by dark matter halos or Milgromian dynamics (MOND). We investigate this by setting up a MOND model of M33. We first simulate it in isolation for 6 Gyr, starting from an initial good match to the rotation curve (RC). Too large a bar and bulge form when the gas is too hot, but this is avoided by reducing the gas temperature. A strong bar still forms in 1 Gyr, but rapidly weakens and becomes consistent with the observed weak bar. Previous work showed this to be challenging in Newtonian models with a live dark matter halo, which developed strong bars. The bar pattern speed implies a realistic corotation radius of 3 kpc. However, the RC still rises too steeply, and the central line-of-sight velocity dispersion (LOSVD) is too high. We then add a constant external acceleration field of 8.4 × 10−12 m s−2 at 30° to the disk as a first-order estimate for the gravity exerted by M31. This suppresses buildup of material at the center, causing the RC to rise more slowly and reducing the central LOSVD. Overall, this simulation bears good resemblance to several global properties of M33, and highlights the importance of including even a weak external field on the stability and evolution of disk galaxies. Further simulations with a time-varying external field, modeling the full orbit of M33, will be needed to confirm its resemblance to observations.

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“…Rather, the number of wide binaries with unphysically high v depends on r sky similarly to the genuine wide binary population, whose contribution can be estimated from the peak in the v distribution at v ≈ 1. This is very suggestive of the expected close binary contamination (Clarke 2020). In addition, stars in binaries with high v have a poorer Gaia astrometric fit (parallax + proper motion), suggestive of photocentre acceleration induced by an undetected close binary companion (Belokurov et al 2020).…”

Section: Using the Velocity Distributionmentioning

confidence: 60%

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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The distribution of relative proper motions of wide binaries in Gaia DR2: MOND or multiplicity?

Cited by 26 publications

References 13 publications

The KBC void and Hubble tension contradict $Λ$CDM on a Gpc scale $-$ Milgromian dynamics as a possible solution

The KBC void and Hubble tension contradict $Λ$CDM on a Gpc scale $-$ Milgromian dynamics as a possible solution

The Global Stability of M33 in MOND

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

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