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The stellar structure and kinematics of dwarf spheroidal galaxies formed by tidal stirring | | Ewa L. Lokas
; Stelios Kazantzidis
; Jaroslaw Klimentowski
; Lucio Mayer
; Simone Callegari
; | | Date: |
27 Jun 2009 | | Abstract: | Using N-body simulations we study the stellar properties of dwarf spheroidal
galaxies formed by tidally-induced morphological transformation of disky dwarfs
on cosmologically-motivated eccentric orbits around the Milky Way. The dwarf
galaxy models initially consist of a stellar disk embedded in an extended
spherical dark matter halo. Depending on the initial orientation of the disk
with respect to the orbital plane, different final configurations are obtained.
The least evolved dwarf is triaxial and retains a significant amount of
rotation. More evolved dwarfs are almost perfect prolate spheroids with little
rotation. We show that the density distribution of stars can in all cases be
approximated by a simple modification of the Plummer law. The kinematics of the
dwarfs is significantly different depending on the line of sight which has
important implications for mapping the observed stellar velocity dispersions of
dwarfs to subhalo circular velocities. When the dwarfs are observed along the
long axis, the measured velocity dispersion is higher and decreases faster with
radius. In the case where rotation is significant, when viewed perpendicular to
the long axis, the effect of minor axis rotation is detected, as expected for
triaxial systems. We model the velocity dispersion profiles and rotation curves
of the dwarfs by solving the Jeans equations for spherical and axisymmetric
systems and adjusting different sets of free parameters, including the total
mass. We find that the mass is typically overestimated when the dwarf is seen
along the long axis and underestimated when the observation is along the short
or intermediate axis. The effect of non-sphericity cannot however bias the
inferred mass by more than 60% in either direction, even for the most strongly
stripped dwarf which is close to disruption. | | Source: | arXiv, 0906.5084 | | Services: | Forum | Review | PDF | Favorites | |
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