Testing the Strong Equivalence Principle. II. Relating the External Field Effect in Galaxy Rotation Curves to the Large-Scale Structure of the Universe

Chae, Kyu-Hyun; Desmond, Harry; Lelli, Federico; McGaugh, Stacy S.; Schombert, James M.

doi:10.48550/arxiv.2109.04745

Cited by 3 publications

(9 citation statements)

References 52 publications

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“…We also illustrate what MOND predicts about internal accelerations within the disk radii with and without EFE, in particular for galaxies, such as dwarf and low surface brightness (LSB) galaxies, whose observed internal accelerations are very weak (<∼ 10 −10.5 m s −2 ) at all radii. Our results will be useful for refining studies of the EFE in rotationallysupported galaxies (Chae et al 2020(Chae et al , 2021.…”

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confidence: 82%

“…The EFE has been derived analytically for the asymptotic regime, far from a bounded mass in AQUAL by Bekenstein & Milgrom (1984), and in QUMOND by Milgrom (2010) and by Banik & Zhao (2015). Based on the asymptotic potentials given in these papers, Chae et al (2021) summarize the azimuthally-averaged radial acceleration in a orbital plane whose axis is tilted by an angle of θ from a constant external field. From the Appendix A of Chae et al (2021) the AQUAL theory has the asymptotic radial acceleration far away from a bounded mass distribution:…”

Section: Methodsmentioning

confidence: 99%

“…Based on the asymptotic potentials given in these papers, Chae et al (2021) summarize the azimuthally-averaged radial acceleration in a orbital plane whose axis is tilted by an angle of θ from a constant external field. From the Appendix A of Chae et al (2021) the AQUAL theory has the asymptotic radial acceleration far away from a bounded mass distribution:…”

Section: Methodsmentioning

confidence: 99%

“…There have been observational indications of the action of the EFE in various galactic systems, e.g., dwarf satellites of the Andromeda galaxy, which are subject to the field of Andromeda (McGaugh & Milgrom 2013), disk galaxies from the Spitzer Photometry and Accurate Rotation Curves (SPARC; database in the fields of external mass concentrations, and ultra-diffuse galaxies (UDGs) in the field of the Coma cluster. Chae et al (2020Chae et al ( , 2021 have used a simple approximate model of the EFE (Famaey & Mc-Gaugh 2012), analyzing the rotation curves (RCs) of more than 150 SPARC galaxies and inferred the values of the external fields in which they fall. 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.…”

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confidence: 99%

“…Published analyses of RCs (e.g. Haghi et al 2016;Hees et al 2016;Chae et al 2020Chae et al , 2021 were based on an approximate analytical formula from , or on numerical simulation results for spherical galaxies (Haghi et al 2019). These models are first-order approximations in that the one-dimensional model of is based on the assumption that the external field is always aligned with the internal radial acceleration, and the simulation results by Haghi et al (2019) are for velocity dispersions in spherical systems.…”

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confidence: 99%

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

Chae,

Milgrom

2022

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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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confidence: 82%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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

Chae,

Milgrom

2022

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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

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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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The Effect of Adiabatic Compression on Dark Matter Halos and the Radial Acceleration Relation

Li,

McGaugh,

Lelli

et al. 2022

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We use a semi-empirical model to investigate the radial acceleration relation (RAR) in a cold dark matter (CDM) framework. Specifically, we build 80 model galaxies covering the same parameter space as the observed galaxies in the SPARC database, assigning them to dark matter halos using abundance matching and halo mass-concentration relations. We consider several abundance matching relations, finding some to be a better match to the kinematic data than others. We compute the unavoidable gravitational interactions between baryons and their dark matter halos, leading to an overall compression of the original NFW halos. Before halo compression, high-mass galaxies approximately lie on the observed RAR whereas low-mass galaxies display up-bending "hooks" at small radii due to DM cusps, making them deviate systematically from the observed relation. After halo compression, the initial NFW halos become more concentrated at small radii, making larger contributions to rotation curves. This increases the total accelerations, moving all model galaxies away from the observed relation. These systematic deviations suggest that the CDM model with abundance matching alone cannot explain the observed RAR. Further effects (e.g., feedback) would need to counteract the compression with precisely the right amount of halo expansion, even in high mass galaxies with deep potential wells where such effects are generally predicted to be negligible.

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Testing the Strong Equivalence Principle. II. Relating the External Field Effect in Galaxy Rotation Curves to the Large-Scale Structure of the Universe

Cited by 3 publications

References 52 publications

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

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

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

The Effect of Adiabatic Compression on Dark Matter Halos and the Radial Acceleration Relation

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