Effects of rotational disruption on the evolution of grain size
  distribution in galaxies
  Interstellar dust grains can be spun up by radiative torques, and the
resulting centrifugal force may be strong enough to disrupt large dust grains.
We examine the effect of this rotational disruption on the evolution of grain
size distribution in galaxies. To this goal, we modify our previous model by
assuming that rotational disruption is the major small-grain production
mechanism. We find that rotational disruption can have a large influence on the
evolution of grain size distribution in the following two aspects especially
for composites and grain mantles (with tensile strength $\sim 10^7$ erg
cm$^{-3}$). First, because of the short time-scale of rotational disruption,
the small-grain production occurs even in the early phase of galaxy evolution.
Therefore, even though stars produce large grains, the abundance of small
grains can be large enough to steepen the extinction curve. Secondly,
rotational disruption is important in determining the maximum grain radius,
which regulates the steepness of the extinction curve. For compact grains with
tensile strength $\gtrsim 10^9$ erg cm$^{-3}$, the size evolution is
significantly affected by rotational disruption only if the radiation field is
as strong as (or the dust temperature is as high as) expected for starburst
galaxies. For compact grains, rotational disruption predicts that the maximum
grain radius becomes less than 0.2 $\mu$m for galaxies with a dust temperature
$\gtrsim 50$ K.
