title: Radial accumulation of dust particles and their maximum density by non-uniform gas density distribution in protoplanetary disks

authors: Tetsuo Taki, Masaki Fujimoto, Shigeru Ida

abstract: We have investigated the radial migration of dust particles due to drag force from
the protoplanetary disk gas, taking into account back-reaction from the 
dust particles to the gas consistently with local 1-D hydrodynamical simulation and 
super-particle approximation.
In the process of planetesimal formation, spiral-in of dust particles toward the host star
is the most serious difficulty.
One of the mechanisms to halt the spiral-in is a radial pressure bump
in the disk, at which local super-Keplerian flow exists.
However, according to accumulation of dust particles at
the super/sub-Keplerian region, the dust frictional force alters 
gas density profile (e,g., Kato et al. , 2012 ) �D
We find that when a dust-to-gas mass ratio goes up to ~1, the pressure bump
is smoothed out and further dust accumulation is inhibited. 
We discuss the halting mechanism in details and possibility of
planetesimal formation.