Roškar, Rok and Debattista, Victor P. and Brooks, Alyson M. and Quinn, Thomas R. and Brook, Chris B. and Governato, Fabio and Dalcanton, Julianne J. and Wadsley, James (2010) Misaligned angular momentum in hydrodynamic cosmological simulations: warps, outer discs and thick discs. Monthly Notices of the Royal Astronomical Society, 408 (2). pp. 783-796. ISSN 0035-8711 http://resolver.caltech.edu/CaltechAUTHORS:20101102-093403133
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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.
|Additional Information:||© 2010 The Authors. Journal compilation © 2010 RAS. Accepted 2010 June 9. Received 2010 June 9; in original form 2010 May 5. The authors thank the hospitality of KITP at UCSB where this work was initiated. RR thanks A. Stilp for the use of her code to produce HI maps and P. Jonsson for his SUNRISE radiative transfer code and comments on the manuscript. RR also thanks R. de Jong for fruitful discussions regarding warps. RR was supported by the NSF grant CAREER AST 02-38683 (also partially supporting JJD) and NSF ITR grant PHY 02-05413 (also partially supporting TRQ and FG) at the University of Washington. VPD was supported by an RCUK Fellowship at the University of Central Lancashire. AB acknowledges funding from the Sherman Fairchild Foundation. FG acknowledges support from HST GO-1125, NSF grant AST-0607819 and NASA ATP NNX08AG84G. Simulations were carried out on TeraGrid resources at TACC, SDSC and PSC as well as additional resources at ARSC. Analysis was performed on resources purchased with the help of the University of Washington Student Technology Fee.|
|Subject Keywords:||Galaxy: stellar content; galaxies: evolution; galaxies: kinematics and dynamics; galaxies: spiral; galaxies: stellar content|
|Official Citation:||Roškar, R., Debattista, V. P., Brooks, A. M., Quinn, T. R., Brook, C. B., Governato, F., Dalcanton, J. J. and Wadsley, J. (2010), Misaligned angular momentum in hydrodynamic cosmological simulations: warps, outer discs and thick discs. Monthly Notices of the Royal Astronomical Society, 408: 783–796. doi: 10.1111/j.1365-2966.2010.17178.x|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Jason Perez|
|Deposited On:||03 Nov 2010 18:35|
|Last Modified:||26 Dec 2012 12:35|
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