Disk galaxy rotation curves
Dilip G. Banhatti1 and Rahul Datta2
1School of Physics, Madurai Kamaraj University, Madurai
2Space Applications Centre, ISRO, Ahmedabad
E-mail: dilip.g.banhatti@gmail.com

Abstract. We show that simple axisymmetric Newtonian calculation suffices to consistently connect disk galaxy rotation curves to underlying mass distribution and vice versa, without need for any dark matter. To this end, we connect mass density profiles of five galaxies of varying sizes with observed galaxy rotation curves. The five galaxies are: NGC6822 (4.8 kpc), Large Magellanic Cloud (9 kpc), The Milky Way (17 kpc), NGC3198 (30 kpc) and UGC9133 (102.5 kpc). The mass and mass density profiles of these galaxies have been computed using the scientific computing s/w package MATLAB taking the already available velocity profiles of the galaxies as the input, and without considering any dark matter contribution. We have plotted these profiles after computing them according to three different theories of gravity (and dynamics): Newtonian, Modified Newtonian Dynamics (MOND) and Vacuum Modified Gravity. We also consider how the profile due to the Newtonian theory would modify if we use a cosmological constant = 5 × 10-56 cm-2. Comparing these mass and mass density profiles, we try to form an idea regarding what could be a realistic theory of gravity and whether we need dark matter to explain the results.