  Recently revealed differences in planets around M dwarf vs. solar-type stars
could arise from differences in their primordial disks, and surveys of T Tauri
stars find a correlation between stellar mass and disk mass. "Minimum" disks
have been reconstructed for the Solar System and solar-type stars and here this
exercise is performed for M dwarfs using Kepler-detected planets. Distribution
of planet mass between current orbits produces a disk with total mass of
~0.009Msun and a power-law profile with index 2.2. Disk reconstruction from the
output of a forward model of planet formation indicates that the effect of
detection bias on disk profile is slight and that the observed scatter in
planet masses and semi-major axes is consistent with a universal disk profile.
This nominal M dwarf disk is more centrally concentrated than those inferred
around the solar-type stars observed by Kepler, and the mass surface density
beyond 0.02 AU is sufficient for in situ accretion of planets as single
embryos. The mass of refractory solids within 0.5 AU is 5.6Mearth compared to
4Mearth for solar-type stars, in contrast with the trend with total disk mass.
The total solids beyond 0.5 AU is sufficient for the core of at least one giant
planet.
