Dynamics of dwarf galaxies in $f(R)$ gravity

Abstract

We use the kinematic data of the stars in eight dwarf spheroidal galaxies to assess whether $f(R)$ gravity can fit the observed profiles of the line-of-sight velocity dispersion of these systems without resorting to dark matter. Our model assumes that each galaxy is spherically symmetric and has a constant velocity anisotropy parameter $\beta$ and constant mass-to-light ratio consistent with stellar population synthesis models. We solve the spherical Jeans equation that includes the Yukawa-like gravitational potential appearing in the weak field limit of $f(R)$ gravity, and a Plummer density profile for the stellar distribution. The $f(R)$ velocity dispersion profiles depend on two parameters: the scale length ${\xi }^{-1}$, below which the Yukawa term is negligible, and the boost of the gravitational field $\delta >-1$. $\delta$ and $\xi$ are not universal parameters, but their variation within the same class of objects is expected to be limited. The $f(R)$ velocity dispersion profiles fit the data with a value ${\xi }^{-1}=1.2_{-0.9}^{+18.6}$ Mpc for the entire galaxy sample. On the contrary, the values of $\delta$ show a bimodal distribution that picks at $\bar{\delta }=-0.986\pm 0.002$ and $\bar{\delta }=-0.92\pm 0.01$. These two values disagree at $6\sigma$ and suggest a severe tension for $f(R)$ gravity. It remains to be seen whether an improved model of the dwarf galaxies or additional constraints provided by the proper motions of stars measured by future astrometric space missions can return consistent $\delta$'s for the entire sample and remove this tension.

11 pages, 4 figures, 2 Tables. Accepted for publication on MNRAS

References in corpus (23)

• Unified cosmic history in modified gravity: from F(R) theory to Lorentz non-invariant models
• Models of f(R) Cosmic Acceleration that Evade Solar-System Tests
• Too big to fail? The puzzling darkness of massive Milky Way subhaloes
• Disappearing cosmological constant in f(R) gravity
• Class of viable modified $f(R)$ gravities describing inflation and the onset of accelerated expansion
• The Cosmology of f(R) Gravity in the Metric Variational Approach
• Velocity Dispersion Profiles of Seven Dwarf Spheroidal Galaxies
• The Newtonian Limit of F(R) gravity
• Solar system and equivalence principle constraints on f(R) gravity by chameleon approach
• Stellar Velocities in the Carina, Fornax, Sculptor and Sextans dSph Galaxies: Data from the Magellan/MMFS Survey
• The Velocity Dispersion Profile of the Remote Dwarf Spheroidal Galaxy Leo I: A Tidal Hit and Run?
• Exploring Halo Substructure with Giant Stars X. Extended Dark Matter or Tidal Disruption?: The Case for the Leo I Dwarf Spheroidal Galaxy
• Clean Kinematic Samples in Dwarf Spheroidals: An Algorithm for Evaluating Membership and Estimating Distribution Parameters When Contamination is Present
• Stellar kinematics in the remote Leo II dwarf spheroidal galaxy -- Another brick in the wall
• Modeling The Structure And Dynamics of Dwarf Spheroidal Galaxies with Dark Matter And Tides
• Proper Motions of Dwarf Spheroidal Galaxies from Hubble Space Telescope Imaging. IV: Measurement for Sculptor
• The Araucaria Project. The Distance to the Sculptor dwarf spheroidal galaxy from infrared photometry of RR Lyrae stars
• Dark matters on the scale of galaxies
• The Variable Stars of the Draco Dwarf Spheroidal Galaxy - Revisited
• Leo V: Spectroscopy of a Distant and Disturbed Satellite
• Einstein, Planck and Vera Rubin: relevant encounters between the Cosmological and the Quantum Worlds
• Faint objects in motion: the new frontier of high precision astrometry
• The proper motion of stars in dwarf galaxies: distinguishing central density cusps from cores

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• Dynamics of Dwarf Galaxies in Scalar-Tensor-Vector-Gravity
• Dwarf galaxies in non-local gravity