On the lifetime of discs around late type stars
  We address the question of whether protoplanetary discs around low mass stars
(e.g. M-dwarfs) may be longer lived than their solar-type counterparts. This
question is particularly relevant to assess the planet-making potential of
these lower mass discs. Given the uncertainties inherent to age-dating young
stars, we propose an alternative approach that is to analyse the spatial
distribution of disc-bearing low-mass stars and compare it to that of
disc-bearing solar-type stars in the same cluster. A significant age difference
between the two populations should be reflected in their average nearest
neighbour distance (normalised to the number of sources), where the older
population should appear more spread out.
  To this aim, we perform a Minimum Spanning Tree (MST) analysis on the spatial
distribution of disc-bearing young stellar objects (YSOs) in six nearby low
mass star forming regions. We find no evidence for significant age differences
between the disc-bearing low-mass (later than M2) and 'solar-type' (earlier
than M2) stars in these regions. We model our results by constructing and
analysing synthetic fractal distributions that we evolve for typical values of
the velocity dispersions. A comparison of simple models to our MST analysis
suggests that the lifetime of discs around M-stars is similar to that of discs
around solar-type stars. Furthermore, a model-independent spatial analysis of
the observations robustly shows that any age differences between the two
samples must be smaller than the average age difference between disc-bearing
classical T-Tauri stars and disc-less Weak-Lined T-Tauri stars.
