2019/10/31 by Tousif Islam
Physics and Astronomy · #Astrophysics #Cosmology and Gravitation Theories #Dark matter #Galaxies: Formation, Evolution, Phenomena #Galaxy #Galaxy formation and evolution #Galaxy rotation curve #Lambda #Mathematical physics #Modified Newtonian dynamics #Physics #Quantum mechanics #Sigma #Solar and Space Plasma Dynamics #Velocity dispersion #gr-qc
paper · pdf · doi:10.1103/physrevd.102.024068
published as Phys. Rev. D 102, 024068 (2020) · 10 pages, 7 figures
openalex publication_date 2020/07/22 · arxiv created 2020/08/02 · arxiv updated 2020/08/04 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Recent observations of anomalous line-of-sight velocity dispersions of two ultradiffuse galaxies (UDGs) provide a stringent test for modified gravity theories. While NGC 1052-DF2 exhibits an extremely low dispersion value (\ensuremathσ\ensuremath∼7.8_\ensuremath-2.2+5.6 km/s), the reported dispersion value for NGC 1052-DF44 is quite high (\ensuremathσ\ensuremath∼41.0\ifmmode±\else\textpm\fi8 km/s). For DF2, the dynamical mass is almost equal to the luminous mass suggesting the galaxy have little to no ``dark matter'' in \mathrm\ensuremathΛCDM whereas DF4 requires a dynamical mass-to-light ratio of \ensuremath∼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 [T. Islam and K. Dutta, Phys. Rev. D 100, 104049 (2019)], 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.