Misaligned angular momentum in hydrodynamic cosmological simulations: warps, outer discs and thick discs

Type Journal Article
Names Rok RoŇ°kar, Victor P. Debattista, Alyson M. Brooks, Thomas R. Quinn, Chris B. Brook, Fabio Governato, Julianne J. Dalcanton, James Wadsley
Publication Monthly Notices of the Royal Astronomical Society
Volume 408
Issue 2
Pages 783-796
Date October 1, 2010
Short Title Misaligned angular momentum in hydrodynamic cosmological simulations
URL http://adsabs.harvard.edu/abs/2010MNRAS.408..783R
Library Catalog NASA ADS
Abstract We present a detailed analysis of a disc galaxy forming in a high-resolution fully cosmological simulation to investigate the nature of the outer regions of discs and their relevance for the disc formation process. Specifically, we focus on the phenomenon of misaligned disc components and find that the outer disc warp is a consequence of the misalignment between the inner disc and the surrounding hot gaseous halo. As the infalling cold gas sinks towards the centre of the galaxy, it is strongly torqued by the hot gas halo. By the time the fresh gas reaches the central disc-forming region, its angular momentum is completely aligned with the spin of the hot gas halo. If the spin of the hot gas halo, in turn, is not aligned with that of the inner disc, a misaligned outer disc forms, comprised of newly accreted material. The inner and outer components are misaligned with each other because they respond differently to infalling substructure and accretion. The warped disc feeds the main gas disc due to viscous angular momentum losses, but small amounts of star formation in the warp itself form a low-metallicity thick disc. We show that observations of resolved stellar populations in warped galaxies in the local Universe could provide evidence for the presence of these processes and therefore indirectly reveal ongoing gas accretion and the existence of hot gas haloes.
Tags GALAXIES: EVOLUTION, GALAXIES: STELLAR CONTENT, Galaxy: Stellar Content, galaxies: kinematics and dynamics, galaxies: spiral
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