The stellar velocity dispersion in nearby spirals: radial profiles and correlations

Journal article, 2019

The stellar velocity dispersion, σ, is a quantity of crucial importance for spiral galaxies, where it enters fundamental dynamical processes such as gravitational instability and disc heating. Here we analyse a sample of 34 nearby spirals from the Calar Alto Legacy Integral Field Area (CALIFA) spectroscopic survey, deproject the line-of-sight σ to σR, and present reliable radial profiles of σR as well as accurate measurements of (σR), the radial average of σR over one effective (half-light) radius. We show that there is a trend for σR to increase with decreasing R, that (σR) correlates with stellar mass (M∗), and tested correlations with other galaxy properties. The most significant and strongest correlation is the one with M: (σR) ∞ M∗0.5. This tight scaling relation is applicable to spiral galaxies of type Sa-Sd and stellar mass M∗ ≈ 109.5 -1011.5 M. Simple models that relate σR to the stellar surface density and disc scale length roughly reproduce that scaling, but overestimate (σR) significantly.