Abstract
We investigate angular momentum acquisition in Milky Way sized galaxies by
comparing five high resolution zoom-in simulations, each implementing identical
cosmological initial conditions, but utilizing different hydrodynamic codes:
Enzo, Art, Ramses, Arepo, and Gizmo-PSPH. Each code implements a distinct set
of feedback and star formation prescriptions. We find that while many galaxy
and halo properties vary between the different codes (and feedback
prescriptions), there is qualitative agreement on the process of angular
momentum acquisition in the galaxy's halo. In all simulations, cold filamentary
gas accretion to the halo results in ~4 times more specific angular momentum in
cold halo gas ($łambda_cold 0.15$) than in the dark matter halo. At
z>1, this inflow frequently results in the formation of transient cold flow
disks---large co-rotating gaseous structures in the halo of the galaxy that are
fueled, aligned, and kinematically connected to filamentary gas infall along
the cosmic web. Due to the qualitative agreement among disparate simulations,
we conclude that the buildup of high angular momentum halo gas and the
transitory formation of cold flow disks are robust predictions of LCDM galaxy
formation. A growing body of observational evidence suggests that this process
is borne out in the real universe.
Description
High Angular Momentum Halo Gas: a Feedback and Code-Independent
Prediction of LCDM
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