Implications and Applications of Kinematic Galaxy Scaling Relations

Abstract EN

Galaxy scaling relations, which describe a connection between ostensibly unrelated physical characteristics, testify to an underlying order in galaxy formation that requires understanding.

I review the development of a scaling relation that (1) unites the well-known fundamental plane (FP) relation of giant elliptical galaxies and Tully-Fisher (TF) relation of disk galaxies, (2) fits low mass spheroidal galaxies, including the ultrafaint satellites of our galaxy, (3) explains the apparent shift of lenticular galaxies relative to both FP or TF, (4) describes all stellar dynamical systems, including systems with no dark matter (stellar clusters), (5) associates explicitly the numerical coefficients that account for the apparent tilt of the FP away from the expectation drawn from the virial theorem with variations in the total mass-to-light ratio of galaxies within the half-light radius, (6) connects with results that demonstrate the robustness of mass estimators when applied at the half-light radius, and (7) results in smaller scatter for disk galaxies than the TF relation.

I review two applications: (1) the cross-calibration of distance measurement methods and (2) the determination of mass-to-light ratios of simple stellar populations and implications for the stellar initial mass function.