Authors: Klypin, Anatoly; Valenzuela, Octavio¹; Colín, Pedro²; Quinn, Thomas³

Source: Monthly Notices of the Royal Astronomical Society, Volume 398, Number 2, September 2009 , pp. 1027-1040(14)

Publisher: Wiley-Blackwell

Abstract:

We study dynamics of bars in models of disc galaxies embedded in realistic dark matter haloes. We find that disc thickness plays an important, if not dominant, role in the evolution and structure of the bars. We also make extensive numerical tests of different N-body codes used to study bar dynamics. Models with thick discs typically used in this type of modelling (height-to-length ratio h_z/R_d= 0.2 ) produce slowly rotating, and very long, bars. In contrast, more realistic thin discs with the same parameters as in our Galaxy (h_z/R_d≈ 0.1) produce bars with normal length R_bar≈R_d , which rotate quickly with the ratio of the corotation radius to the bar radius compatible with observations. Bars in these models do not show a tendency to slow down, and may lose as little as 2-3 per cent of their angular momentum due to dynamical friction with the dark matter over cosmological time. We attribute the differences between the models to a combined effect of high phase-space density and smaller Jeans mass in the thin-disc models, which result in the formation of a dense central bulge. Special attention is paid to numerical effects, such as the accuracy of orbital integration, force and mass resolution. Using three N-body codes -gadget, adaptive refinement tree (art) andpkdgrav- we find that numerical effects are very important and, if not carefully treated, may produce incorrect and misleading results. Once the simulations are performed with sufficiently small time-steps and with adequate force and mass resolution, all the codes produce nearly the same results: we do not find any systematic deviations between the results obtained withtreecodes (gadgetandpkdgrav) and with the adaptive mesh refinement (art) code.

Keywords: methods: N-body simulations; galaxies: evolution; galaxies: haloes; galaxies: kinematics and dynamics

Document Type: Research article

DOI: http://dx.doi.org/10.1111/j.1365-2966.2009.15187.x

Affiliations: 1: Instituto de Astronomía, Universidad Nacional Autónoma de México, A.P. 70-264, 04510, Mexico D.F., Mexico 2: Centro de Radiostronomía y Astrofísica, UNAM, Apartado Postal 72-3 (Xangari), 58089 Morelia, Mexico 3: Department of Astronomy, University of Washington, Seattle, WA 98195-1580, USA

Publication date: 2009-09-01

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