Fitting functions for a disk-galaxy model with different ΛCDM-halo profiles

摘要

Aims. We present an adaptation of the standard scenario of disk-galaxy formation to the concordant CDMcosmology aimed to derive analytical expressions for the scale lengthand rotation speed of present-day disks that form within fourdifferent, cosmologically motivated protogalactic dark matterhalo-density profiles. Methods. We invoke a standard galaxy-formation model thatincludes virial equilibrium of spherical dark halos, specific angularmomentum conservation during gas cooling, and adiabatic halo responseto the gas inflow. The mean mass-fraction and mass-to-light ratio ofthe central stellar disk are treated as free parameters whose valuesare tuned to match the zero points of the observed size-luminosity andcircular speed-luminosity relations of galaxies. Results. We supply analytical formulas for the characteristic size and rotation speed of disks built inside Einasto r1/6,Hernquist, Burkert, and Navarro-Frenk-White dark matter halos. Theseexpressions match simultaneously the observed zero points and slopes ofthe different correlations that can be built in the space of disk galaxies from plausible values of the galaxy- and star-formation efficiencies. Key words: dark matter - galaxies: formation - galaxies: fundamental parameters - galaxies: spiral - galaxies: structure