We derive the mass weighted total density slopes within the effective ( half-light ) radius , \gamma ^ { \prime } , for more than 2000 nearby galaxies from the SDSS-IV MaNGA survey using Jeans-anisotropic-models applied to IFU observations .
Our galaxies span a wide range of the stellar mass ( 10 ^ { 9 } M _ { \odot } < M _ { * } < 10 ^ { 12 } M _ { \odot } ) and the velocity dispersion ( 30 km/s < \sigma _ { v } < 300 km/s ) .
We find that for galaxies with velocity dispersion \sigma _ { v } > 100 km/s , the density slope has a mean value \langle \gamma ^ { \prime } \rangle = 2.24 and a dispersion \sigma _ { \gamma } = 0.22 , almost independent of velocity dispersion .
A clear turn over in the \gamma ^ { \prime } - \sigma _ { v } relation is present at \sigma \sim 100 km/s , below which the density slope decreases rapidly with \sigma _ { v } .
Our analysis shows that a large fraction of dwarf galaxies ( below M _ { * } = 10 ^ { 10 } M _ { \odot } ) have total density slopes shallower than 1 , which implies that they may reside in cold dark matter halos with shallow density slopes .
We compare our results with that of galaxies in hydrodynamical simulations of EAGLE , Illustris and IllustrisTNG projects , and find all simulations predict shallower density slopes for massive galaxies with high \sigma _ { v } .
Finally , we explore the dependence of \gamma ^ { \prime } on the positions of galaxies in halos , namely centrals vs. satellites , and find that for the same velocity dispersion , the amplitude of \gamma ^ { \prime } is higher for satellite galaxies by about 0.1 .