birth sizes are in agreement with constraints from the current observed size distribution of the asteroid belt [@Morbidelli+etal2009] and Neptune Trojans [@SheppardTrujillo2010].

Some of the open questions related to this picture of planetesimal formation is to what degree the results of [@Johansen+etal2007] are affected by the fact that self-gravity was turned on after particles had concentrated in a pressure bumps and how the emergence and amplitude of pressure bumps are affected by numerical resolution. In this paper we present high-resolution and long-time-integration simulations of planetesimal formation in turbulence caused by the magnetorotational instability (MRI). We find that the large-scale geostrophic pressure bumps that are responsible for particle concentration are sustained when going from moderate ($256^3$) to high ($512^3$) resolution. Particle concentration in these pressure bumps is also relatively independent on resolution. We present a long-time-integration simulation performed at moderate resolution ($256^3$) where particles and self-gravity are started at the same time, in contrast to earlier simulations where self-gravity was not turned on until a strong concentration event occurred (J07). We also study the initial burst of planetesimal formation at $512^3$ resolution. We present evidence for collisions between gravitationally bound clumps, observed at both moderate and high resolution, and indications that 