The SAMI galaxy survey: Mass-kinematics scaling relations

We use data from the Sydney-AAO Multi-object Integral-field spectroscopy (SAMI) Galaxy Survey to study the dynamical scaling relation between galaxy stellar mass M_∗ and the general kinematic parameter S_K = √KV²_rot + σ² that combines rotation velocity Vrot and velocity dispersion σ. We show that the logM_∗ - logSK relation: (1) is linear above limits set by properties of the samples and observations; (2) has slightly different slope when derived from stellar or gas kinematic measurements; (3) applies to both early-type and late-type galaxies and has smaller scatter than either the Tully.Fisher relation (logM_∗ - log V_rot) for late types or the Faber.Jackson relation (logM_∗ - log σ) for early types; and (4) has scatter that is only weakly sensitive to the value of K, with minimum scatter for K in the range 0.4 and 0.7. We compare SK to the aperture second moment (the 'aperture velocity dispersion') measured from the integrated spectrum within a 3-arcsecond radius aperture (σ_3″ ). We find that while SK and σ_3″ are in general tightly correlated, the logM_∗ - log SK relation has less scatter than the logM_∗ - log σ_3″ relation.