Some Stars are Totally Metal: A New Mechanism Driving Dust Across
  Star-Forming Clouds, and Consequences for Planets, Stars, and Galaxies
  Dust grains in neutral gas behave as aerodynamic particles, so they can
develop large density fluctuations independent of gas density fluctuations.
Specifically, gas turbulence can drive order-of-magnitude 'resonant'
fluctuations in the dust on scales where the gas stopping/drag timescale is
comparable to the turbulent eddy turnover time. Here we show that for large
grains (size >0.1 micron, containing most grain mass) in sufficiently large
molecular clouds (radii >1-10 pc, masses >10^4 M_sun), this scale becomes
larger than the characteristic sizes of pre-stellar cores (the sonic length),
so large fluctuations in the dust-to-gas ratio are imprinted on cores. As a
result, star clusters and protostellar disks formed in large clouds should
exhibit significant abundance spreads in the elements preferentially found in
large grains. This naturally predicts populations of carbon-enhanced stars,
certain highly unusual stellar populations observed in nearby open clusters,
and may explain the 'UV upturn' in early-type galaxies. It will also
dramatically change planet formation in the resulting protostellar disks, by
preferentially 'seeding' disks with an enhancement in large carbonaceous or
silicate grains. The relevant threshold for this behavior scales simply with
cloud densities and temperatures, making straightforward predictions for
clusters in starbursts and high-redshift galaxies. Because of the selective
sorting by size, this process is not necessarily visible in extinction mapping.
We also predict the shape of the abundance distribution -- when these
fluctuations occur, a small fraction of the cores may actually be seeded with
abundances ~100 times the mean, such that they are almost 'totally metal'
(Z~1)! Assuming the cores collapse, these totally metal stars would be rare (1
in 10^4 in clusters where this occurs), but represent a fundamentally new
stellar evolution channel.
