Abstract
The mass density profiles of 18 early-type galaxies are investigated in this work, and we hope to know whether these galaxies are core-like or cusp-like from the analysis. We started from the simplest case, those with anisotropy parameter β=0, and derived the predicted velocity dispersion analytically from Jeans equation with two spherically symmetric models. We fitted the observational data with the theoretical velocity dispersion and obtained the best-fit parameter set of the mass density function. Then we grouped the galaxies into four catagories according to the reduced chi-square results. Our results imply that Jaffe model is appropriate to fit galaxies with central rising in the velocity dispersion profile. Galaxies which are Jaffe-model preferred are likely to have cusp structure in the density distribution. The M_bh-σ relation of our samples was also established, which was log(M_bh/M_sun)=(8.35±0.06)+(4.84±0.02)log(σ/200kms^(-1)). The figure shows that galaxies that can not be fitted well by both models tend to have larger black-hole masses.