Modified Newtonian Dynamics (MOND) is one of the most popular alternative
theories of dark matter to explain the missing mass problem in galaxies.
Although it remains controversial regarding MOND as a fundamental theory, MOND
phenomenology has been shown to widely apply in different galaxies, which gives
challenges to the standard Ξ cold dark matter model. In this article,
we derive analytically the galactic rotation curve gradient in the MOND
framework and present a rigorous analysis to examine the MOND phenomenology in
our Galaxy. By assuming a benchmark baryonic disk density profile and two
popular families of MOND interpolating functions, we show for the first time
that the recent discovery of the declining Galactic rotation curve in the outer
region (Rβ17β23 kpc) can almost rule out the MOND phenomenology at
more than 5Ο. This strongly supports some of the previous studies
claiming that MOND is neither a fundamental theory nor a universal description
of galactic properties.Comment: Accepted in Ap