Eppur si muove: Positional and kinematic correlations of satellite pairs
  in the low Z universe
  We have recently shown (Ibata et al. 2014) that pairs of satellite galaxies
located diametrically opposite each other around their host possess
predominantly anti-correlated velocities. This is consistent with a scenario in
which $\sim 50$% of satellite galaxies belong to kinematically-coherent
rotating planar structures, similar to those detected around the giant galaxies
of the Local Group. Here we extend this analysis, examining the incidence of
satellites of giant galaxies drawn from an SDSS photometric redshift catalog.
We find that there is a $\sim 17$% overabundance ($> 3 \sigma$ significance) of
candidate satellites at positions diametrically opposite a spectroscopically
confirmed satellite. We show that cosmological simulations do not possess this
property when the contamination is included, and that there are in fact, after
subtracting contamination, 2 to 3 times more satellites diametrically opposed
to a spectroscopically confirmed satellite than at $90\deg$ from it. We also
examine the correlation between the satellite pair positions and the
orientation of the host galaxy major axis. We find that those satellite pairs
with anti-correlated velocities have a strong preference ($\sim 3:1$) to align
with the major axis of the host whereas those with correlated velocities
display the opposite behavior. This correlation of the satellite alignments
appears to be stronger than the well-documented preference of satellites to be
located close to the major axis of their host. We finally show that repeating a
similar analysis to Ibata et al. (2014) with same-side satellites is generally
hard to interpret, but is not inconsistent with our previous results when
strong quality-cuts are applied on the sample. All these unexpected
correlations strongly suggest that a substantial fraction of satellite galaxies
are causally-linked in their formation and evolution.
