New H-band galaxy number counts:: a large local hole in the galaxy distribution

We examine H-band number counts determined using new photometry over two fields with a combined solid angle of 0.30 deg(2) to H approximate to 19, as well as bright data (H <= 14) from the two-Micron All-Sky Survey (2MASS). First, we examine the bright number counts from 2MASS extracted for the approximate to 4000-deg(2) Automated Plate Measuring machine (APM) survey area situated around the southern Galactic pole. We find a deficiency of approximate to 25 per cent at H = 13 with respect to homogeneous predictions, in line with previous results in the B and K, bands. In addition, we examine the bright counts extracted for \b\ > 20 degrees (covering approximate to 27 000 deg(2)); we find a relatively constant deficit in the counts of approximate to 15-20 per cent to H = 14. We investigate various possible causes for these results; namely, errors in the model normalization, unexpected luminosity evolution (at low and high redshifts), errors in the photometry, incompleteness and large-scale structure. In order to address the issue of the model normalization, we examine the number counts determined for the new faint photometry presented in this work and also for faint data (H less than or similar to 20) covering 0.39 deg(2) from the Las Campanas Infrared Survey (LCIRS). In each case a zero-point is chosen to match that of the 2MASS photometry at bright magnitudes using several hundred matched point sources in each case. We find a large offset between 2MASS and the LCIRS data of 0.28 +/- 0.01 mag. Applying a consistent zero-point, the faint data, covering a combined solid angle of 0.69 deg(2), is in good agreement with the homogeneous prediction used previously, with a best-fitting normalization a factor of 1.095(-0.034)(+0.035) higher. Addressing the contribution from large-scale structure, we estimate the cosmic variance in the bright counts over the APM survey area and for \b\ > 20 degrees expected in a Lambda cold dark matter (Lambda CDM) cosmology using 27 mock 2MASS catalogues constructed from the Lambda CDM Hubble Volume simulation. The APM survey area bright counts are in line with a rare fluctuation in the local galaxy distribution of approximate to 2-3 sigma. The \b\ > 20 degrees counts represent a 2.5-4 sigma fluctuation and would imply a local hole which extends over the entire local galaxy distribution, which may start to be at odds with Lambda CDM. The increase in faint near-infrared data from the UK Infrared Deep Sky Survey should help to resolve this issue.