We present CloudFlex, a new open-source tool for predicting the
absorption-line signatures of cool gas in galaxy halos with complex small-scale
structure. Motivated by analyses of cool material in hydrodynamical simulations
of turbulent, multiphase media, we model individual cool gas structures as
assemblies of cloudlets with a power-law distribution of cloudlet mass βmclβΞ±β and relative velocities drawn from a turbulent velocity
field. The user may specify Ξ±, the lower limit of the cloudlet mass
distribution (mcl,minβ), and several other parameters that set the
total mass, size, and velocity distribution of the complex. We then calculate
the MgII 2796 absorption profiles induced by the cloudlets along pencil-beam
lines of sight. We demonstrate that at fixed metallicity, the covering fraction
of sightlines with equivalent widths W2796β<0.3 Ang increases
significantly with decreasing mcl,minβ, cool cloudlet number density
(nclβ), and cloudlet complex size. We then present a first application,
using this framework to predict the projected W2796β distribution around
βΌLβ galaxies. We show that the observed incidences of W2796β>0.3
Ang sightlines within 10 kpc < Rβ₯β < 50 kpc are consistent with our
model over much of parameter space. However, they are underpredicted by models
with mcl,minββ₯100Mββ and nclββ₯0.03cmβ3, in
keeping with a picture in which the inner cool circumgalactic medium (CGM) is
dominated by numerous low-mass cloudlets (mclββ²100Mββ)
with a volume filling factor β²1%. When used to simultaneously model
absorption-line datasets built from multi-sightline and/or spatially-extended
background probes, CloudFlex will enable detailed constraints on the size and
velocity distributions of structures comprising the photoionized CGM.Comment: 22 pages, 7 figures. Submitted to AAS Journals, with minor
modifications. Comments welcome. (1) Co-first authors who made equal
contributions to this wor