Discussing the first velocity dispersion profile of an ultra-diffuse galaxy in MOND

Abstract

Using Jeans modelling, we calculate the velocity dispersion profile of the ultra-diffuse galaxy (UDG) Dragonfly 44 in MOND. For the nominal mass-to-light ratio from the literature and an isotropic profile, the agreement with the data is excellent near the center of the galaxy. However, in modified gravity, close to the cluster core, the gravitational environment should bring the galaxy back towards the Newtonian behavior. This success of the isolated MOND prediction for the central velocity dispersion could then mean that the galaxy is at large distances ($\gg 5$ Mpc) from the cluster core, as hinted by the fact that close-by UDGs share similar velocities with a dispersion well below that of the cluster itself. There is however a two-sigma tension in the outer part of the UDG due to an increase of the observed dispersion profile with respect to the flat MOND prediction. This deviation could simply be a measurement error. Other possibilities could be, for a UDG far from the cluster, a higher-than-nominal baryonic mass with a tangentially anisotropic dispersion profile, or even a sign of a dark baryonic halo. If the UDG is closer to the cluster core, the deviation could be a sign that it is in the process of disruption.

5 pages, 2 figures. Accepted for publication in A&A Letters

References in corpus (17)

• Forty-Seven Milky Way-Sized, Extremely Diffuse Galaxies in the Coma Cluster
• One Law To Rule Them All: The Radial Acceleration Relation of Galaxies
• NIHAO XI: Formation of Ultra-Diffuse Galaxies by outflows
• A High Stellar Velocity Dispersion and ~100 Globular Clusters for the Ultra Diffuse Galaxy Dragonfly 44
• A second galaxy missing dark matter in the NGC1052 group
• The Dragonfly Nearby Galaxies Survey. II. Ultra diffuse galaxies near the elliptical galaxy NGC 5485
• Milky Way potentials in CDM and MOND. Is the Large Magellanic Cloud on a bound orbit?
• The ultra-diffuse galaxy NGC 1052-DF2 with MUSE: II. The population of DF2: stars, clusters and planetary nebulae
• Discovery of a close pair of faint dwarf galaxies in the halo of Centaurus A
• A population of faint low surface brightness galaxies in the Perseus cluster core
• The evolution of ultra-diffuse galaxies in nearby galaxy clusters from the Kapteyn IAC WEAVE INT Clusters Survey ($\text{KIWICS}$)
• Deep Imaging of the HCG 95 Field.I.Ultra-diffuse Galaxies
• Marriage à-la-MOND: Baryonic dark matter in galaxy clusters and the cooling flow puzzle
• A tidal tale: detection of multiple stellar streams in the environment of NGC1052
• Predicted MOND velocity dispersions for a catalog of ultra-diffuse galaxies in group environments
• Constraints on the HI Mass of NGC 1052-DF2
• MOND and the dark baryons

Cited by in corpus (8)

• From galactic bars to the Hubble tension: weighing up the astrophysical evidence for Milgromian gravity
• The distribution and morphologies of Fornax Cluster dwarf galaxies suggest they lack dark matter
• A spectroscopic study of MATLAS-2019 with MUSE: an ultra-diffuse galaxy with an excess of old globular clusters
• 3D hydrodynamic simulations for the formation of the Local Group satellite planes
• Probing the radial acceleration relation and the strong equivalence principle with the Coma cluster ultra-diffuse galaxies
• The phantom dark matter halos of the Local Volume in the context of modified Newtonian dynamics
• Scale-invariant dynamics in the Solar System
• Simulations of cluster ultra-diffuse galaxies in MOND