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

TL;DR

This study analyzes stellar velocity dispersion profiles in 34 nearby spiral galaxies, revealing a strong correlation between radial velocity dispersion and stellar mass, and providing insights into galaxy dynamics and disc heating processes.

Contribution

It presents the first reliable radial profiles of stellar velocity dispersion in a sample of nearby spirals, establishing a tight correlation with stellar mass and testing simple dynamical models.

Findings

$\sigma_{R}$ increases towards galaxy centers.

$\langle \sigma_{R} angle$ correlates strongly with stellar mass.

Simple models overestimate the observed velocity dispersions.

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 $\langle\sigma_{R}\rangle$, 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 $\langle\sigma_{R}\rangle$ correlates with stellar mass ($M_{\star}$) and tested correlations with other galaxy properties. The most significant and strongest correlation is the one with $M_{\star}$: $\langle\sigma_{R}\rangle \propto M_{\star}^{0.5}$. 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 $\langle\sigma_{R}\rangle$ significantly.