On the tension between the Radial Acceleration Relation and Solar System quadrupole in modified gravity MOND

Abstract

Modified Newtonian Dynamics (MOND), postulating a breakdown of Newtonian mechanics at low accelerations, has considerable success at explaining galaxy kinematics. However, the quadrupole of the gravitational field of the Solar System (SS) provides a strong constraint on the way in which Newtonian gravity can be modified. In this paper we assess the extent to which the AQUAL and QUMOND modified gravity formulations of MOND are capable of accounting simultaneously for the Radial Acceleration Relation (RAR), the Cassini measurement of the SS quadrupole and the kinematics of wide binaries in the Solar neighbourhood. We achieve this by inferring the location and sharpness of the MOND transition from the SPARC RAR under broad assumptions for the behaviour of the interpolating function and external field effect. We constrain the same quantities from the SS quadrupole, finding that this requires a significantly sharper transition between the deep-MOND and Newtonian regimes than is allowed by the RAR (an 8.7$\sigma$ tension under fiducial model assumptions). This may be relieved somewhat by allowing additional freedom in galaxies' mass-to-light ratios -- which also improves the RAR fit -- and more significantly (to 1.9$\sigma$) by removing galaxies with bulges. For the first time, we also apply to the SPARC RAR fit an AQUAL correction for flattened systems, obtaining similar results. Finally we show that the SS quadrupole constraint implies, to high precision, no deviation from Newtonian gravity in nearby wide binaries, and speculate on possible resolutions of this tension between SS and galaxy data within the MOND paradigm.

16 pages, 11 figures, 3 tables; moderate revision, matches MNRAS published version

References in corpus (25)

• SPARC: Mass Models for 175 Disk Galaxies with Spitzer Photometry and Accurate Rotation Curves
• The Radial Acceleration Relation in Rotationally Supported Galaxies
• One Law To Rule Them All: The Radial Acceleration Relation of Galaxies
• The rotation curves shapes of late-type dwarf galaxies
• THINGS about MOND
• Insight into the baryon-gravity relation in galaxies
• X-ray Group and cluster mass profiles in MOND: Unexplained mass on the group scale
• Milky Way potentials in CDM and MOND. Is the Large Magellanic Cloud on a bound orbit?
• Escaping from MOND
• A statistical investigation of the mass discrepancy-acceleration relation
• The power spectrum of the Milky Way: Velocity fluctuations in the Galactic disk
• External field effect of modified Newtonian dynamics in the Solar system
• The scatter, residual correlations and curvature of the SPARC baryonic Tully-Fisher relation
• Stellar Populations and the Star Formation Histories of LSB Galaxies: III. Stellar Population Models
• A new formulation of the external field effect in MOND and numerical simulations of ultra-diffuse dwarf galaxies $-$ application to NGC 1052-DF2 and NGC 1052-DF4
• Asymmetrical tidal tails of open star clusters: stars crossing their cluster's prah challenge Newtonian gravitation
• Stellar streams as gravitational experiments II. Asymmetric tails of globular cluster streams
• Models of modified-inertia formulation of MOND
• Numerical Solutions of the External Field Effect on the Radial Acceleration in Disk Galaxies
• The radial acceleration relation and dark baryons in MOND
• Testing Modified Gravity Theories with Numerical Solutions of the External Field Effect in Rotationally Supported Galaxies
• Robust Evidence for the Breakdown of Standard Gravity at Low Acceleration from Statistically Pure Binaries Free of Hidden Companions
• Coupling the non-gravitational forces and Modified Newton Dynamics for cometary orbits
• MOND as manifestation of modified inertia
• Testing MOND on small bodies in the remote solar system