Fragmentation of protoplanetary disks around M-Dwarfs

Abstract

We investigate planet formation via gravitational instabilities (GI) and protoplanetary disk (PPD) fragmentation around M-Dwarfs. We present the results of a suite of some 70 SPH simulations, with 10^6-particles, of gaseous isothermal PPDs around a star of mass M_sun/3. We scan the parameter space of disk mass, temperature, and radius, bracketing reasonable values based on theoretical and observational considerations. We find that disks with a minimum Toomre Q of Q_min < 0.9 will fragment and form gravitationally bound clumps. We find disk height tends to stabilize disks and can be incorporated with Q to predict fragmentation. We find that disks with initial conditions (ICs) slightly out of equilibrium can fragment for higher Q and present a code for generating equilibrium ICs. We argue that some discrepancies in the literature regarding Q_crit may be due to different methods of generating ICs. We argue that GI likely plays a role in PPDs around M-Dwarfs and that disk fragmentation at large radii is a plausible outcome for these disks.