The necessity of dark matter in MOND within galactic scales

To further test MOdified Newtonian Dynamics (MOND) on galactic scales – originally proposed to explain the rotation curves of disk galaxies without dark matter – we study a sample of six strong gravitational lensing early-type galaxies from the CASTLES database. To determine whether dark matter is present in these galaxies, we compare the total mass (from lensing) with the stellar mass content (from a comparison of photometry and stellar population synthesis). We find that strong gravitational lensing on galactic scales requires a significant amount of dark matter, even within MOND. On such scales a 2 eV neutrino cannot explain this excess matter – in contrast with recent claims to explain the lensing data of the bullet cluster. The presence of dark matter is detected in regions with a higher acceleration than the characteristic MONDian scale of $\sim {10}^{-10}$m/s${}^2$. This is a serious challenge to MOND unless the proper treatment of lensing is qualitatively different (possibly to be developed within a consistent theory such as TeVeS).