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 (v sin i) and macroturbulent velocity dispersions (v(mac)) for 49 southern dwarf stars (including many first-ever measurements). We compare our results with previous values, and estimate rotation periods (P-rot) and sin i values where possible. We confirm that v(mac) generally decreases with decreasing temperature for T-eff greater than or equal to 5000 K. Magnetically active stars tend to show enhanced values of v(mac). 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 Lande g(eff) values, implying the presence of significant surface magnetic flux.