Probing the universality of acceleration scale in the modified Newtonian dynamics with SPARC galaxies

We probe the universality of acceleration scale \begin{document}$ a_0$\end{document} in Milgrom's modified Newtonian dynamics (MOND) using the recently released rotation curve data from SPARC galaxies. We divide the SPARC data into different subsamples according to the morphological types of galaxies, and fit the rotation curve data of each subsample with the theoretical prediction of MOND. MOND involves an arbitrary interpolation function which connects the Newtonian region and the MOND region. Here we consider five different interpolation functions that are widely discussed in the literature. It is shown that the best-fitting \begin{document}$ a_0$\end{document} significantly depends on the interpolation functions. For a specific interpolation function, \begin{document}$ a_0$\end{document} also depends on the morphological types of galaxies, implying that \begin{document}$ a_0$\end{document} may be not a universal constant. Introducing a dipole correction to \begin{document}$ a_0$\end{document} can significantly improve the fits. The dipole directions for four of the five interpolation functions point towards an approximately consistent direction, but \begin{document}$ a_0$\end{document} still varies for different interpolation functions.