Activity and kinematics of low mass stars

Abstract

We present an analysis of the magnetic activity, photometry and kinematics of approximately 70000 M dwarfs from the Sloan digital Sky Survey (SDSS) Data Release 7. This new analysis explores the spatial distribution of these M dwarf properties as a function of vertical distance from the Galactic plane (Z) and distance from the Galactic center (R). We confirm the established trends of decreasing magnetic activity, as measured by Ha emission, with increasing distance from the mid-plane of the disk but also observe a new trend in Galactocentric radius, apparent in the analysis of spectral types M3 and M4 of a small increase in activity with increasing R. Examining the color indices r - z, r - i and g - r from the SDSS ugriz photometry reveals noticeable gradients in the vertical direction but not in the radial direction. To analyze the kinematics we develop a new technique utilizing probability distributions and a pseudo-montecarlo data fitting scheme to determine the parameters (o- 1, pi, 0-2, 12) and normalization of the underlying Gaussians making up the kinematic distributions of the stellar population. We analyze each of the spatial velocities VR, Vz , and Ve defined in a Galactocentric cylindrical coordinate system. The kinematic analysis reproduced previous trends of increasing dispersion with increasing distance from the mid-plane, but with much greater accuracy and reliability and to distances farther out away from the mid-plane. The analysis did not reveal any significant kinematic trends in the radial domain.