The local hole in the galaxy distribution: new optical evidence

We present a new CCD survey of bright galaxies predominantly within the Northern and Southern strips of the 2dF Galaxy Redshift Survey (2dFGRS) areas. We use the new CCD data to check the photographic photometry scales of the 2dFGRS 100-k release, APM Bright Galaxy Catalogue, APM-Stromlo Redshift Survey, Durham-UKST (DUKST) Survey, Millennium Galaxy Catalogue (MGC) and Sloan Digital Sky Survey (SDSS). We find evidence for scale and zero-point errors in the 2dFGRS 100-k release Northern field, DUKST and APM data of 0.10, 0.24 and 0.31 mag, respectively; we find excellent agreement with the MGC and SDSS photometry. We use our new CCD data to correct the photographic photometry, we then compare the CCD number counts in both the Northern and Southern survey areas. We find conclusive evidence that the Southern counts with B < 17 mag are down by 30 per cent relative to both the Northern counts and to the models of Metcalfe et al. in the same magnitude range. We further compare the number redshift distributions from the B < 17 mag Durham-UKST and B < 19.5 2dFGRS redshift surveys using the corrected photometry. While the Northern n(z) from 2dFGRS appears relatively homogeneous over its whole range, the Southern n( z) shows a 30 per cent deficiency out to z = 0.1; at higher redshifts it agrees much better with the Northern n(z) and the homogeneous model n(z). The Durham-UKST n(z) shows that the Southern 'hole' extends over a 20 x 75 deg(2) area. The troughs with z < 0.1 in the Durham-UKST n(z) appear deeper than for the fainter 2dFGRS data. This effect appears to be real since the troughs also appear to deepen in the 2dFGRS data when magnitude-limited at B < 17 mag and so this may be evidence that the local galaxy distribution is biased on greater than or similar to 50 h(-1) Mpc scales which is unexpected in a Lambda CDM cosmology. Finally, since the Southern local void may persist over the full area of the APM and APM Bright Galaxy Catalogue with a approximate to 25 per cent deficiency in the counts below B approximate to 17, this would mean that its extent is approximately 300 h(-1) Mpc x 300 h(-1) Mpc on the sky as well as approximate to 300 h(-1) Mpc in the redshift direction. Such a 25 per cent deficiency extending over approximate to 10(7) h(-3) Mpc(3) may imply that the power-law behaviour of the galaxy correlation function extends to 150 h(-1) Mpc with no break and shows more excess large-scale power than detected in the 2dFGRS correlation function or expected in the Lambda CDM cosmology.