SCYON Abstract

Received on April 7 2004

The Counter-Streaming Instability in Dwarf Ellipticals with Off-Center Nuclei

Authors	S. De Rijcke ¹ and V.P. Debattista ²
Affiliation	¹ Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281, S9, B-9000 Gent, Belgium ² Institut für Astronomie, ETH Hönggerberg, HPF G4.2, CH-8093 Zürich, Switzerland
Accepted by	Astrophysical Journal Letters 2004, 603, L25

Contact	sven.derijcke@UGent.be
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Abstract

In many nucleated dwarf elliptical galaxies (dE,Ns), the nucleus is offset by a significant fraction of the scale radius with respect to the center of the outer isophotes. Using a high-resolution N-body simulation, we demonstrate that the nucleus can be driven off-center by the m = 1 counter-streaming instability, which is strong in flattened stellar systems with zero rotation. The model develops a nuclear offset of the order of one third of the exponential scale-length. We compare our numerical results with photometry and kinematics of FCC046, a Fornax cluster dE,N with a nucleus offset by 1.2''; we find good agreement between the model and FCC046. We also discuss mechanisms that may cause counter-rotation in dE,Ns and conclude that the destruction of box orbits in an initially triaxial galaxy is the most promising.