The Local Hole revealed by galaxy counts and redshifts
  The redshifts of ~250000 galaxies are used to study the Local Hole and its
associated peculiar velocities. The sample, compiled from 6dFGS and SDSS
provides wide sky coverage to a depth of ~300h-1Mpc. We have therefore examined
K and r limited galaxy redshift distributions and number counts to map the
local density field. Comparing observed galaxy n(z) distributions to
homogeneous models in three large regions of the high latitude sky, we find
evidence for under-densities ranging from ~4-40% in these regions to depths of
~150h-1Mpc with the deepest under-density being over the Southern Galactic cap.
Using the Galaxy and Mass Assembly (GAMA) survey we then establish the
normalisation of galaxy counts at fainter magnitudes and thus confirm that the
underdensity over all three fields at K<12.5 is ~15+-3%. Finally, we further
use redshift catalogues to map peculiar velocities over the same areas using
the average redshift - magnitude, zbar(m), technique of Soneira (1979). After
accounting for the direct effect of large-scale structure on zbar(m) we can
then search for peculiar velocities. Taking all three regions into
consideration the data reject at the ~4sigma level the idea that we have
recovered the CMB rest frame in the volume probed. There is therefore some
consistent evidence from counts and Hubble diagram for a local ~150h-1Mpc
underdensity that deeper counts and redshifts in the Northern Galactic cap
suggest may extend to ~300h-1Mpc.
