and $\Sigma_s$ is a density scaling factor. The velocity of circular orbits in this model rises from zero at the galactic center and approaches to the constant value $v_0$ in outer regions where the light profile falls off exponentially. @JHb have derived the gravitational potential corresponding to $\Sigma_D(R)$. I denote this potential by $V_D(R)$. The gradient $$F_H=\frac{d}{dR}\left [V_0(R)-V_D(R)\right ],$$ will give the gravitational force of a spherical dark matter component, computed inside the galactic disk. The density profile of the dark component, $\rho_H$, can then be determined using $F_H$. The positiveness of $\rho_H$ imposes some restrictions on the physical values of $\lambda$ and $\alpha=G\Sigma_s R_D/v_0^2$ as Figure 5 in JH shows. For a given $\lambda$, $\alpha$ cannot exceed a critical value $\alpha_{cr}$. The parameter $\lambda$ determines the shape of the dark matter density profile. A model with $\lambda=1$ and $\alpha=\alpha_{cr}$ is maximal in the region where the rotation curve is rising. i.e., there is no dark matter in that region. Models with $\lambda >1$ and $\alpha=\alpha_{cr}$ are still maximal but only in the vicinity of the center for $R<R_D$. In such models the rotational velocity of stars due to dark matter ($v_H=\sqrt{R F_H}$) has a monotonically rising profile. For $\lambda<1$, 