Rotation, turbulence and evidence for magnetic fields in southern dwarfs

We model high-resolution spectra using a simple radiative transfer analysis to derive projected rotational velocities (u sin i) and macroturbulent velocity dispersions (umac) for 49 southern dwarf stars (including many first-ever measurements). We compare our results with previous values, and estimate rotation periods (Prot) and sin i values where possible. We confirm that vmac generally decreases with decreasing temperature for Teff ≥ 5000 K. Magnetically active stars tend to show enhanced values of vmac. This may be due to a difference in the mean stellar convective properties, a change in the mean stellar temperature structure, or a combination of both. We identify a group of stars that exhibit correlations between the derived velocities and line Landé geft values, implying the presence of significant surface magnetic flux.