Ewa L. Lokas, Stelios Kazantzidis, Lucio Mayer
In recent years the Sloan Digital Sky Survey has unraveled a new population
of ultra-faint dwarf galaxies (UFDs) in the vicinity of the Milky Way (MW)
whose origin is still a puzzle. Using a suite of collisionless N-body
simulations, we investigate the formation of UFDs in the context of the tidal
stirring model for the formation of dwarf spheroidal galaxies in the Local
Group (LG). Our simulations are designed to reproduce the tidal interactions
between MW-sized host galaxies and rotationally supported dwarfs embedded in
10^9 M_sun dark matter (DM) halos. We explore a wide variety of inner density
slopes \rho \propto r^{-\alpha} for the dwarf DM halos, ranging from core-like
(\alpha = 0.2) to cuspy (\alpha = 1), and different dwarf orbital
configurations. Our experiments demonstrate that UFDs can be produced via the
tidal stirring of disky dwarfs on relatively tight orbits, consistent with a
redshift of accretion by the host galaxy of z~1, and with intermediate values
for the halo inner density slopes (\rho \propto r^{-0.6}). The inferred slopes
are in excellent agreement with those resulting from both the modeling of the
rotation curves of dwarf galaxies and recent cosmological simulations of dwarf
galaxy formation. Comparing the properties of observed UFDs with those of their
simulated counterparts, we find remarkable similarities in terms of basic
observational parameters. We conclude that tidal stirring of rotationally
supported dwarfs represents a viable mechanism for the formation of UFDs in the
LG environment.
View original:
http://arxiv.org/abs/1201.5784
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