If true Dark Flow could be one of the most important observations since the CMBR. Looking forward to hearing the latest updates on this discovery. For one thing it would change our views a little on a homogenious and isotropic universe at different scales.
http://www.sciencedaily.com/releases/2010/03/100310162829.htm
http://en.wikipedia.org/wiki/Dark_flow
http://www.kashlinsky.info/anima/skash.nsf/home?OpenForm
"We now summarize the main conclusions from this study:
• Our measurements indicate the existence of the residual CMB dipole evaluated over
the CMB pixels associated with the hot SZ producing gas in clusters of galaxies. The dipole
is measured at high-signifance level (∼ 8σ in the outer bins) and persists out the limit of
our cluster catalog zmedian 0.1. Its direction is not far off the direction of the ”global CMB
dipole” measured from the entire unprocessed maps.
• We show with detailed simulation that the CMB mask and/or cluster sample discreteness
induced cross-talk effects are negligible and cannot mimic the measured dipole.
• The dipole originates exclusively at the cluster pixels and, hence, cannot be produced
by foregrounds or instrument noise. It must originate from the CMB photons that have
passed through the hot gas in the catalog clusters.
• We prove that the signal arises from the hot SZ producing cluster gas because we
demonstrate that in the unfiltered CMB maps there remains statistically significant temperature
decrement as expected from the TSZ effect. Its profile is consistent with the NFW
profile out the largest aperture where we still detect hot gas (∼ 30). At larger radii the
dipole begins to decrease as expected.
• In the filtered maps, designed to reduce the cosmological CMB fluctuations, the dipole
is isolated simultaneously as the monopole component vanishes. This proves that its origin
lies in the KSZ component. The monopole vanishes (within the noise) because for the
NFW profile the gas in hydrostatic equilibrium must have a strong decrease in the X-ray
temperature in the outer parts. This decrease is consistent with the available direct X-ray
measurements, but more importantly is demonstrated empirically in AKKE.
• With the current cluster catalog we determine that the amplitude of the dipole corresponds
to bulk flow of 600-1000 km/sec. This conversion factor, C1,100, may however
have some systematic offset related to our current cluster modelling. However, this possible
uncertainty only affect the amplitude of the motion, not its coherence scale or existence.
• The cosmological implications are discussed in Kashlinsky et al (2008). We show
there that the concordance ΛCDM model cannot account for this motion at many standard
deviations. Instead, it is possible that this motion extends all the way to the current cosmological
horizon and may originate from the tilt across the observable Universe from far away
pre-inflationary inhomogeneities (Kashlinsky et al 1994; Turner 1991)."
I suggest they prove their method by looking in a few other directions to see if there are other dark flows or if this a unique one off event.
