The SAMI Galaxy Survey: mass-kinematics scaling relations

Abstract

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 = \sqrt{K V_rot^2 + σ ^2} that combines rotation velocity Vrot and velocity dispersion σ. We show that the log M∗ - log SK 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 (log M∗ - log Vrot) for late types or the Faber-Jackson relation (log M∗ - 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 log M∗ - log SK relation has less scatter than the \log M_* - \log σ _{3^' ' }} relation.