GALAXY LUMINOSITY FUNCTION AND TULLY-FISHER RELATION: RECONCILED THROUGH ROTATION-CURVE STUDIES

International audienceThe relation between galaxy luminosity L and halo virial velocity nu(vir) required to fit the galaxy luminosity function differs from the observed Tully-Fisher relation between L and disk speed nu(rot). Because of this, the problem of reproducing the galaxy luminosity function and the Tully-Fisher relation simultaneously has plagued semianalytic models since their inception. Here we study the relation between nu(rot) and vvir by fitting observational average rotation curves of disk galaxies binned in luminosity. We show that the nu(rot)-nu(vir) relation that we obtain in this way can fully account for this seeming inconsistency. Therefore, the reconciliation of the luminosity function with the Tully-Fisher relation rests on the complex dependence of nu(rot) on nu(vir), which arises because the ratio of stellar mass to dark matter mass is a strong function of halo mass