Recent observations of ultra-dwarf galaxy NGC1052-DF2 started an interesting discussion between dark matter hypothesis and modified gravity theories .
Reported low velocity dispersion ( < 10.5 km/s at 90 \% confidence level ) derived from the kinematic data of 10 globular clusters in the galaxy points towards an extraordinarily low dynamical mass ( \sim 3.4 \times 10 ^ { 8 } M _ { \odot } ) which is of the same order of the luminous mass ( \sim 2.0 \times 10 ^ { 8 } M _ { \odot } ) in the galaxy .
This has been interpreted as the first evidence of a galaxy ‘ without Dark Matter ’ .
It has been argued that dark matter is not necessarily coupled to the the baryonic mass on the galactic scale and poses a challenge to modified gravity theories .
We explore the dynamics of NGC1052-DF2 within the context of four popular alternative theories of gravity [ Modified Newtonian Dynamcies ( MOND ) , Weyl Conformal gravity , Modified gravity ( MOG ) /Scalar-Tensor-Vector Gravity ( STVG ) and Verlinde ’ s Emergent gravity ] and present the analysis of detailed radial variation of the velocity dispersion .
We demonstrate that the dispersion data of NGC1052-DF2 is fully consistent with modified gravity paradigm ( as well as with general relativity without dark matter ) .
We reach similar conclusion for the ultra-dwarf NGC1052-DF4 which has been claimed to be the second candidate for galaxies ‘ without Dark Matter ’ .