Physical Properties of Complex C Halo Clouds

Type Journal Article
Names W.-H. Hsu, M. E. Putman, F. Heitsch, S. Stanimirović, J. E. G. Peek, S. E. Clark
Publication The Astronomical Journal
Volume 141
Issue 2
Pages 57
Date February 1, 2011
URL http://adsabs.harvard.edu/abs/2011AJ....141...57H
Library Catalog NASA ADS
Abstract 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 log (N(log (mass)))/log (mass), 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 101.1-104.8 M sun, sizes of 101.2-102.6 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 8.4 × 10-5 (60 kpc/d) cm-3. 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.
Tags Galaxy: Formation, Galaxy: halo, ISM: clouds, ISM: structure, intergalactic medium
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