Galactic kinematics with modified Newtonian dynamics

Abstract

We look for observational signatures that could discriminate between Newtonian and modified Newtonian (MOND) dynamics in the Milky Way, in view of the advent of large astrometric and spectroscopic surveys. Indeed, a typical signature of MOND is an apparent disk of "phantom" dark matter, which is uniquely correlated with the visible disk-density distribution. Due to this phantom dark disk, Newtonian models with a spherical halo have different signatures from MOND models close to the Galactic plane. The models can thus be differentiated by measuring dynamically (within Newtonian dynamics) the disk surface density at the solar radius, the radial mass gradient within the disk, or the velocity ellipsoid tilt angle above the Galactic plane. Using the most realistic possible baryonic mass model for the Milky Way, we predict that, if MOND applies, the local surface density measured by a Newtonist will be approximately 78 Msun/pc2 within 1.1 kpc of the Galactic plane, the dynamically measured disk scale-length will be enhanced by a factor of 1.25 with respect to the visible disk scale-length, and the local vertical tilt of the velocity ellipsoid at 1 kpc above the plane will be approximately 6 degrees. None of these tests can be conclusive for the present-day accuracy of Milky Way data, but they will be of prime interest with the advent of large surveys such as GAIA.

5 pages

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Cited by in corpus (27)

• Modified Newtonian Dynamics (MOND): Observational Phenomenology and Relativistic Extensions
• Structure and Kinematics of the Stellar Halos and Thick Disks of the Milky Way Based on Calibration Stars from SDSS DR7
• A direct dynamical measurement of the Milky Way's disk surface density profile, disk scale length, and dark matter profile at 4 kpc < R < 9 kpc
• From galactic bars to the Hubble tension: weighing up the astrophysical evidence for Milgromian gravity
• THINGS about MOND
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• Weighing the local dark matter with RAVE red clump stars
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• The Surface Density Profile of the Galactic Disk from the Terminal Velocity Curve
• Kinematical and chemical vertical structure of the Galactic thick disk I. Thick disk kinematics
• No evidence for a dark matter disk within 4 kpc from the Galactic plane
• Implications of a time-varying Galactic potential for determinations of the dynamical surface density
• Testing modified Newtonian dynamics in the Milky Way
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• Mass models from high-resolution HI data of the dwarf galaxy NGC 1560
• Stellar kinematics from the symmetron fifth force in the Milky Way disk
• Barred spiral galaxies in modified gravity theories
• Testing Dark Matter and Modifications to Gravity using Local Milky Way Observables
• Stellar Accelerations and the Galactic Gravitational Field
• Potential-density pairs and vertical tilt of the stellar velocity ellipsoid
• The dynamical phase transitions of stellar systems and the corresponding kinetimacs
• Sedna and the cloud of comets surrounding the Solar System in Milgromian dynamics
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• On the separation between baryonic and dark matter: evidence for phantom dark matter?
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• The Futile Search for Galactic Disk Dark Matter
• MOND and Methodology