Alexandra Abate, Hume A. Feldman
In this paper we search for a signature of a large scale bulk flow by looking
for fluctuations in the magnitudes of distant LRGs. We take a sample of LRGs
from the Sloan Digital Sky Survey with redshifts of z>0.08 over a contiguous
area of sky. Neighboring LRG magnitudes are averaged together to find the
fluctuation in magnitudes as a function of R.A.. The result is a fluctuation of
a few percent in flux across roughly 100 degrees. The source of this
fluctuation could be from a large scale bulk flow or a systematic in our
treatment of the data set, or the data set itself. A bulk flow model is fitted
to the observed fluctuation, and the three bulk flow parameters, its direction
and magnitude: alpha_b, delta_b, v_b are constrained. We find that the bulk
flow direction is consistent with the direction found by other authors, with
alpha_b 180, delta_b -50. The bulk flow magnitude however was found to be
anomalously large with v_b>4000km/s. The LRG angular selection function cannot
be sufficiently taken into account in our analysis with the available data, and
may be the source of either the anomalous magnitude of the bulk flow signal, or
possibly the entire fluctuation. However, the fluctuation indicates a bulk flow
direction very close to those found using other data sets and analyses. Further
investigation with upcoming data is required to confirm this detection.
View original:
http://arxiv.org/abs/1106.5791
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