Dark halo response and the stellar initial mass function in early-type and late-type galaxies

Understand

We investigate the origin of the relations between stellar mass and optical circular velocity for early-type (ETG) and late-type (LTG) galaxies --- the Faber-Jackson (FJ) and Tully-Fisher (TF) relations.

• We combine measurements of dark halo masses (from satellite kinematics and weak lensing), and the distribution of baryons in galaxies (from a new compilation of galaxy scaling relations), with constraints on dark halo structure from cosmological simulations.
• The principle unknowns are the halo response to galaxy formation and the stellar initial mass function (IMF).
• The slopes of the TF and FJ relations are naturally reproduced for a wide range of halo response and IMFs.