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{Comparison of mass density profiles of galaxies of varying sizes based onsome gravity theories from observed galaxy rotation curves and assessing theneed for dark matter.} We present an analysis of the rotation curves of fivegalaxies of varying galactic radii: NGC6822 (4.8 kpc), Large Magellanic Cloud(9 kpc), The Milky Way (17 kpc), NGC3198 (30 kpc) and UGC9133 (102.5 kpc). Themass and mass density profiles of these galaxies have been computed using thescientific computing s/w package MATLAB taking the already available velocityprofiles of the galaxies as the input, and without considering any Dark Mattercontribution. We have plotted these profiles after computing them according tothree different theories of gravity (and dynamics): Newtonian (black line),Modified Newtonian Dynamics (MoND) (green line) and Vacuum Modified Gravity(red line). We also consider how the profile due to the Newtonian theory wouldmodify if we take into account a small negative value of the CosmologicalConstant (5 x 10^-56 cm^-2 from theory) (blue line). Comparing these mass andmass density profiles, we try to form an idea regarding what could be arealistic theory of gravity and whether we need Dark Matter to explain theresults. Keywords : disk galaxy rotation curves, galaxy mass, mass densityprofile, dark matter, Newtonian theory, MoND, Vacuum Modified Gravity, negativecosmological constant

Mass Distribution, Rotation Curves and Gravity Theories