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Title:
Tidal evolution of discy dwarf galaxies in the Milky Way potential: the formation of dwarf spheroidals
Authors:
Klimentowski, Jarosław; Łokas, Ewa L.; Kazantzidis, Stelios; Mayer, Lucio; Mamon, Gary A.
Affiliation:
AA(Nicolaus Copernicus Astronomical Center, Bartycka 18, 00-716 Warsaw, Poland), AB(Nicolaus Copernicus Astronomical Center, Bartycka 18, 00-716 Warsaw, Poland), AC(Center for Cosmology and Astro-Particle Physics, Department of Physics and Department of Astronomy, The Ohio State University, Physics Research Building, 191 West Woodruff Avenue, Columbus, OH 43210, USA), AD(Institute for Theoretical Physics, University of Zürich, CH-8057 Zürich, Switzerland; Institute of Astronomy, Department of Physics, ETH Zürich, Wolfgang-Pauli Strasse, CH-8093 Zürich, Switzerland), AE(Institut d'Astrophysique de Paris (UMR 7095: CNRS and Université Pierre & Marie Curie), 98 bis Bd Arago, F-75014 Paris, France; GEPI (UMR 8111: CNRS and Université Denis Diderot), Observatoire de Paris, F-92195 Meudon, France)
Publication:
Monthly Notices of the Royal Astronomical Society, Volume 397, Issue 4, pp. 2015-2029. (MNRAS Homepage)
Publication Date:
08/2009
Origin:
MNRAS
MNRAS Keywords:
galaxies: dwarf , galaxies: fundamental parameters , galaxies: kinematics and dynamics , Local Group , cosmology: dark matter
DOI:
10.1111/j.1365-2966.2009.15046.x
Bibliographic Code:
2009MNRAS.397.2015K

Abstract

We conduct high-resolution collisionless N-body simulations to investigate the tidal evolution of dwarf galaxies on an eccentric orbit in the Milky Way (MW) potential. The dwarfs originally consist of a low surface brightness stellar disc embedded in a cosmologically motivated dark matter halo. During 10 Gyr of dynamical evolution and after five pericentre passages, the dwarfs suffer substantial mass loss and their stellar component undergoes a major morphological transformation from a disc to a bar and finally to a spheroid. The bar is preserved for most of the time as the angular momentum is transferred outside the galaxy. A dwarf spheroidal (dSph) galaxy is formed via gradual shortening of the bar. This work thus provides a comprehensive quantitative explanation of a potentially crucial morphological transformation mechanism for dwarf galaxies that operates in groups as well as in clusters. We compare three cases with different initial inclinations of the disc and find that the evolution is fastest when the disc is coplanar with the orbit. Despite the strong tidal perturbations and mass loss, the dwarfs remain dark matter dominated. For most of the time, the one-dimensional stellar velocity dispersion, σ, follows the maximum circular velocity, Vmax, and they are both good tracers of the bound mass. Specifically, we find that Mbound ~ V3.5max and in agreement with earlier studies based on pure dark matter simulations. The latter relation is based on directly measuring the stellar kinematics of the simulated dwarf, and may thus be reliably used to map the observed stellar velocity dispersions of dSphs to halo circular velocities when addressing the missing satellites problem.
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