The Launching of Cold Clouds by Galaxy Outflows I: Hydrodynamic
  Interactions with Radiative Cooling
  To better understand the nature of the multiphase material found in
outflowing galaxies, we study the evolution of cold clouds embedded in flows of
hot and fast material. Using a suite of adaptive-mesh refinement simulations
that include radiative cooling, we investigate both cloud mass loss and cloud
acceleration under the full range of conditions observed in galaxy outflows.
The simulations are designed to track the cloud center of mass, enabling us to
study the cloud evolution at long disruption times. For supersonic flows, a
Mach cone forms around the cloud, which damps the Kelvin-Helmholtz instability
but also establishes a streamwise pressure gradient that stretches the cloud
apart. If time is expressed in units of the cloud crushing time, both the cloud
lifetime and the cloud acceleration rate are independent of cloud radius, and
we find simple scalings for these quantities as a function of the Mach number
of the external medium. A resolution study suggests that our simulations have
sufficient resolution to accurately describe the evolution of cold clouds in
the absence of thermal conduction and magnetic fields, physical processes whose
roles will be studied in forthcoming papers.
