Anisotropic Formation of Magnetized Cores in Turbulent Clouds
  In giant molecular clouds (GMCs), shocks driven by converging turbulent flows
create high-density, strongly-magnetized regions that are locally sheetlike. In
previous work, we showed that within these layers, dense filaments and embedded
self-gravitating cores form by gathering material along the magnetic field
lines. Here, we extend the parameter space of our three-dimensional, turbulent
MHD core formation simulations. We confirm the anisotropic core formation model
we previously proposed, and quantify the dependence of median core properties
on the pre-shock inflow velocity and upstream magnetic field strength. Our
results suggest that bound core properties are set by the total dynamic
pressure (dominated by large-scale turbulence) and thermal sound speed c_s in
GMCs, independent of magnetic field strength. For models with Mach number
between 5 and 20, the median core masses and radii are comparable to the
critical Bonnor-Ebert mass and radius defined using the dynamic pressure for
P_ext. Our results correspond to M_core = 1.2 c_s^4/sqrt(G^3 rho_0 v_0^2) and
R_core = 0.34 c_s^2/sqrt(G rho_0 v_0^2) for rho_0 and v_0 the large-scale mean
density and velocity. For our parameter range, the median M_core ~ 0.1-1 M_sun,
but a very high pressure cloud could have lower characteristic core mass. We
find cores and filaments form simultaneously, and filament column densities are
a factor ~2 greater than the surrounding cloud when cores first collapse. We
also show that cores identified in our simulations have physical properties
comparable to those observed in the Perseus cloud. Superthermal cores in our
models are generally also magnetically supercritical, suggesting that the same
may be true in observed clouds.
