The boundaries of Doppler imaging: Starspot patterns on M dwarfs

With the advent of 8-m class telescopes and model atmospheres incorporating molecular opacities a great deal of interest has been directed towards the previously unexplored cool, low mass stars. M dwarfs are obviously a prime target for Doppler imaging studies. Surface maps of starspot locations, morphologies and starspot coverage allow direct comparisons with similar maps of stars at earlier spectral types to be made. For observations at multiple epochs, it becomes possible to measure the latitudinal surface differential rotation which is of interest in stellar dynamo modelling, especially in stars approaching the fully convective limit. Such studies still require S/N enhancement techniques such as least squares deconvolution to reliably constrain high resolution images. We show current results from observations of the brightest early M dwarfs, made with 4-m class telescopes, and examine future prospects for studies of later spectral types.