SFDM: A new formation mechanism of tidal debris
  Recent observations of tidal debris around galaxies have revealed that the
structural properties of the spheroidal components of tidally disturbed
galaxies are similar to those found in non-interacting early-type
galaxies(ETGs), likely due to minor merging events that do not strongly affect
the bulge region or to major mergers that happened a long time ago. We show
that independently of merger events, tidal features like shells or rings can
also arise if the the dark matter is an ultra light scalar field of mass
~10$^{-22}$eV/c$^2$. In the scalar field dark matter (SFDM) model the small
mass precludes halo formation below ~10$^8$ M$_{\odot}$ reducing the number of
small galaxies today, it produces shallow density profiles due to the
uncertainty principle in contrast to the steep profiles found in the standard
cold dark matter (CDM) paradigm, in addition to the usual soliton solution
there exists dark matter haloes in multistates, characterized by ripples in
their density profiles, which are stable provided that most of the halo mass
resides in the ground state. We use the hydrodynamics code ZEUS to track the
gas evolution in a background potential given by a superposition of the ground
and first excited state of the scalar field, we study this configuration when
it is initially unstable (excited state more massive than ground state) but by
a population inversion in the states it eventually becomes stable, this could
happen when haloes decoupled from the expansion of the universe and collapse to
reach a state of equilibrium. We found that tidal structures like rings are
formed at a particular radii as a direct consequence of the wavelike structure
of the dark matter halo(abridged)
