SIMBAD references

We study how stellar rotation curves (RCs) of galaxies are correlated on average with morphology and stellar mass (M_star) using the final release of Sloan Digital Sky Survey IV MaNGA data. We use the visually assigned T-types for the morphology indicator, and adopt a functional form for the RC that can model non-flat RCs at large radii. We discover that within the radial coverage of the MaNGA data, the popularly known flat rotation curve at large radii applies only to the particular classes of galaxies, i.e., massive late types (T-type >= 1, M_star >= 10^10.8M_☉) and S0 types (T-type = -1 or 0, M_star >= 10^10.0M_☉). The RC of late-type galaxies at large radii rises more steeply as M_star decreases, and its slope increases to about +9 km s^–1 kpc^–1 at M_star ≃ 10^9.7M_☉. By contrast, elliptical galaxies (T-type <= -2) have descending RCs at large radii. Their slope becomes more negative as M_star decreases, and reaches as negative as -15 km s^–1 kpc^–1 at M_star ≃ 10^10.2M_☉. We also find that the inner slope of the RC is highest for elliptical galaxies with M_star ≃ 10^10.5M_☉, and decreases as T-type increases or M_star changes away from 10^10.5M_☉. The velocity at the turnover radius R_t is higher for higher M_star, and R_t is larger for higher M_star and later T-types. We show that the inner slope of the RC is coupled with the central surface stellar mass density, which implies that the gravitational potential of central regions of galaxies is dominated by baryonic matter. With the aid of simple models for matter distribution, we discuss what determines the shapes of RCs.