Physical Properties of Complex C Halo Clouds

Observations from the Galactic Arecibo L-band Feed Array H i (GALFA-H i ) Survey of the tail of Complex C are presented and the halo clouds associated with this complex are cataloged. The properties of the Complex C clouds are compared to clouds cataloged at the tail of the Magellanic Stream to provide insight into the origin and destruction mechanism of Complex C. Magellanic Stream and Complex C clouds show similarities in their mass distributions (slope = −0.7 and −0.6 , respectively) and have a common line width of 20–30 km s −1 (indicative of a warm component), which may indicate a common origin and/or physical process breaking down the clouds. The clouds cataloged at the tail of Complex C extend over a mass range of 10 1.1 –10 4.8 M ☉ , sizes of 10 1.2 –10 2.6 pc, and have a median volume density and pressure of 0.065 cm −3 and ( P / k ) = 580 K cm −3 . We do not see a prominent two-phase structure in Complex C, possibly due to its low metallicity and inefficient cooling compared to other halo clouds. Assuming that the Complex C clouds are in pressure equilibrium with a hot halo medium, we find a median halo density of 5.8 × 10 −4 cm −3 , which given a constant distance of 10 kpc is at a z -height of ∼3 kpc. Using the same argument for the Stream results in a median halo density of . These densities are consistent with previous observational constraints and cosmological simulations. We also assess the derived cloud and halo properties with three-dimensional grid simulations of halo H i clouds and find that the temperature is generally consistent within a factor of 1.5 and the volume densities, pressures, and halo densities are consistent within a factor of three.