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

Abstract

The stellar velocity dispersion, $\sigma$, 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 $\sigma$ to ${\sigma }_R$ and present reliable radial profiles of ${\sigma }_R$ as well as accurate measurements of $⟨{\sigma }_R⟩$, the radial average of ${\sigma }_R$ over one effective (half-light) radius. We show that there is a trend for ${\sigma }_R$ to increase with decreasing $R$, that $⟨{\sigma }_R⟩$ correlates with stellar mass ($M_{\star }$) and tested correlations with other galaxy properties. The most significant and strongest correlation is the one with $M_{\star }$: $⟨{\sigma }_R⟩\propto M_{\star }^{0.5}$. This tight scaling relation is applicable to spiral galaxies of type Sa $\mbox{--}$ Sd and stellar mass $M_{\star}\approx10^{9.5}\mbox{--}10^{11.5}\ \mbox{M}_{\odot}$. Simple models that relate ${\sigma }_R$ to the stellar surface density and disc scale length roughly reproduce that scaling, but overestimate $⟨{\sigma }_R⟩$ significantly.

MNRAS, in press