Enigmatic Velocity Dispersions of Ultra-Diffuse Galaxies in Light of Modified Gravity Theories and Radial Acceleration Relation

Abstract

Recent observations of anomalous line-of-sight velocity dispersions of two ultra-diffuse galaxies (UDGs) provide a stringent test for modified gravity theories. While NGC 1052-DF2 exhibits an extremely low dispersion value ($\sigma \sim 7.8_{-2.2}^{+5.6}$ km/s), the reported dispersion value for NGC 1052-DF44 is quite high ($\sigma \sim 41.0\pm 8$ km/s). For DF2, the dynamical mass is almost equal to the luminous mass suggesting the galaxy have little to no `dark matter' in $\Lambda$CDM whereas DF4 requires a dynamical mass-to-light ratio of $\sim 30$ making it to be almost entirely consists of dark matter. It has been claimed that both these galaxies, marking the extreme points in terms of the estimated dynamical mass-to-light ratio among known galaxies, would be difficult to explain in modified gravity scenarios. Extending the analysis presented in \cite{islam2019modified}, we explore the dynamics of DF2 and DF44 within the context of three popular alternative theories of gravity [Modified Newtonian Dynamics (MOND), Weyl Conformal gravity and Modified gravity (MOG)] and examine their viability against the dispersion data of DF2 and DF44. We further show that the galactic `Radial Acceleration Relation' (RAR) is consistent with DF44 dispersion data but not with DF2.

arXiv comment10 pages, 7 figures

References in corpus (37)

• Modified Newtonian Dynamics (MOND): Observational Phenomenology and Relativistic Extensions
• Modified Newtonian Dynamics as an Alternative to Dark Matter
• The Radial Acceleration Relation in Rotationally Supported Galaxies
• Scalar-Tensor-Vector Gravity Theory
• A galaxy lacking dark matter
• Alternatives to Dark Matter and Dark Energy
• One Law To Rule Them All: The Radial Acceleration Relation of Galaxies
• A High Stellar Velocity Dispersion and ~100 Globular Clusters for the Ultra Diffuse Galaxy Dragonfly 44
• The MOG weak field approximation and observational test of galaxy rotation curves
• A second galaxy missing dark matter in the NGC1052 group
• Fitting galactic rotation curves with conformal gravity and a global quadratic potential
• Impact of a global quadratic potential on galactic rotation curves
• A distance of 13 Mpc resolves the claimed anomalies of the galaxy lacking dark matter
• Are galactic rotation curves really flat?
• THINGS about MOND
• Rotational Velocity Curves in the Milky Way as a Test of Modified Gravity
• Tidal stripping as a possible origin of the ultra diffuse galaxy lacking dark matter
• Testing modified gravity with globular cluster velocity dispersions
• Fundamental parameter-free solutions in Modified Gravity
• Ultra-diffuse galaxies without dark matter
• Fitting dwarf galaxy rotation curves with conformal gravity
• MOND and the dynamics of NGC1052-DF2
• 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
• Using globular clusters to test gravity in the weak acceleration regime
• A Deficit of Dark Matter from Jeans Modeling of the Ultra-diffuse Galaxy NGC 1052-DF2
• Using globular clusters to test gravity in the weak acceleration regime: NGC 7099
• Modified Gravity (MOG) fits to observed radial acceleration of SPARC galaxies
• NGC 1052-DF2 And Modified Gravity (MOG) Without Dark Matter
• The Star Formation History and Dynamics of the Ultra-diffuse Galaxy Dragonfly 44 in MOND and MOG
• X-ray clusters of galaxies in conformal gravity
• A scenario for ultra-diffuse satellite galaxies with low velocity dispersions: the case of [KKS 2000]04
• Modified Gravity Theories in Light of the Anomalous Velocity Dispersion of NGC1052-DF2
• A new method to constrain the origins of dark matter-free galaxies and their unusual globular clusters
• The radial acceleration relation and dark baryons in MOND
• Testing Weyl Gravity at Galactic and Extra-galactic Scales
• Globular clusters as a probe for Weyl Conformal Gravity
• Radial Acceleration and Tully-Fisher Relations in Conformal Gravity

Cited by in corpus (5)

• DHOST gravity in Ultra-diffuse galaxies -- Part II: NGC 1052-DF4 and Dragonfly 44
• Challenges in modeling the dark matter halo of NGC 1052-DF2: Cored versus cuspy halo models
• Testing non-local gravity through Ultra-Diffuse Galaxies kinematics
• Velocity dispersion of dark matter deficient ultra-diffuse galaxies: A case for modified gravity
• DHOST gravity in Ultra-diffuse galaxies -- Part I: the case of NGC1052-DF2