A new spin on disks of satellite galaxies
  We investigate the angular and kinematic distributions of satellite galaxies
around a large sample of bright isolated primaries in the spectroscopic and
photometric catalogues of the Sloan Digital Sky Survey (SDSS). We detect
significant anisotropy in the spatial distribution of satellites. To test
whether this anisotropy could be related to the rotating disks of satellites
recently found by Ibata et al. in a sample of SDSS galaxies, we repeat and
extend their analysis. Ibata et al. found an excess of satellites on opposite
sides of their primaries having anticorrelated radial velocities. We find that
this excess is sensitive to small changes in the sample selection criteria
which can greatly reduce its significance. In addition, we find no evidence for
correspondingly correlated velocities for satellites observed on the same side
of their primaries, which would be expected for rotating disks of satellites.
We conclude that the detection of coherent rotation in the satellite population
in current observational samples is not robust. We compare our data to the
$\Lambda$CDM Millennium simulations populated with galaxies according to the
semi-analytic model of Guo et al. We find excellent agreement with the spatial
distribution of satellites in the SDSS data and the lack of a strong signal
from coherent rotation.
