On the alleged duality of the Galactic halo
  We examine the kinematics of the Galactic halo based on SDSS/SEGUE data by
Carollo et al. (2007, 2010). We find that their claims of a counter-rotating
halo are the result of substantial biases in distance estimates (of order 50%):
the claimed retrograde component, which makes up only a tiny fraction of the
entire sample, prone to contaminations, is identified as the tail of distance
overestimates. The strong overestimates also result in a lift in the vertical
velocity component, which explains the large altitudes those objects were
claimed to reach. Errors are worst for the lowest metallicity stars, which
explains the metal-poor nature of the artificial component. We also argue that
measurement errors were not properly accounted for and that the use of Gaussian
fitting on intrinsically non-Gaussian Galactic components invokes the
identification of components that are distorted or even artificial. Our
evaluation of the data leads to a revision of the estimated velocity ellipsoids
and does not yield any reliable evidence for a counterrotating halo component.
If a distinct counterrotating halo component exists it must be far weaker than
claimed by Carollo et al. Finally we note that their revised analysis presented
in Beers et al. (2011) does not alleviate our main concerns.
