An Extremely Deep, Wide-Field Near-Infrared Survey: Bright Galaxy Counts and Local Large Scale Structure

Abstract

We present a deep, wide-field near-infrared (NIR) survey over five widely separated fields at high Galactic latitude covering a total of ∼ 3 deg 2 in J, H, and K s . The deepest areas of the data (∼ 0.25 deg 2 ) extend to a 5 σ limiting magnitude of JHK s > 24 in the AB magnitude system. Although depth and area vary from field to field, the overall depth and large area of this dataset make it one of the deepest wide-field NIR imaging surveys to date. This paper discusses the observations, data reduction, and bright galaxy counts in these fields. We compare the slope of the bright galaxy counts with the Two Micron All Sky Survey (2MASS) and other counts from the literature and explore the relationship between slope and supergalactic latitude. The slope near the supergalactic equator is sub-Euclidean on average pointing to the possibility of a decreasing average space density of galaxies by ∼ 10 − 15% over scales of ∼ 250 − 350 Mpc. On the contrary, the slope at high supergalactic latitudes is strongly super-Euclidean on average suggesting an increase in the space density of galaxies as one moves from the voids just above and below the supergalactic plane out to distances of ∼ 250 − 350 Mpc. These results suggest that local large scale structure could be responsible for large discrepancies in the measured slope between different studies in the past. In addition, the local universe away from the supergalactic plane appears to be underdense by ∼ 25 − 100% relative to the space densities of a few hundred megaparsecs distant. Subject headings: cosmology: observations and large scale structure of universe -galaxies: fundamental parameters (counts) -infrared: galaxies

Homogeneity and isotropy in the Two Micron All Sky Survey Photometric Redshift catalogue

“…Similar positive deviations have also been reported by other studies (Sandage et al 1972;Afshordi et al 2004). As noted by Keenan et al (2010), a positive deviation with respect to the homogeneous β = 0.6 value also suggests that the local Universe could be under-dense on scales of a few hundred Mpc. This underdensity could have an impact in explaining the differences between local measurements of the expansion rate and those derived from CMB observations (Keenan et al 2012).…”

Testing for a Large Local Void by Investigating the Near-Infrared Galaxy Luminosity Function

“…The existence of a large local void would be consistent with studies of near-infrared (NIR) galaxy counts that have found the local space density of galaxies may be low by 25%-50% compared with the density at distances of ∼300 h −1 Mpc or z ∼ 0.1 (Keenan et al 2010b;Busswell et al 2004;Frith et al 2003Frith et al , 2005Huang et al 1997). Galaxy counts in the NIR at low redshifts are primarily sampling L ∼ L * or brighter galaxies (Barro et al 2009).…”

The galaxy luminosity function and the Local Hole

“…More recently Keenan et al (2010Keenan et al ( , 2012 and Keenan, Barger & Cowie (2013) have compared galaxy counts and luminosity density at high and low redshift and reported evidence for a 300 Mpc void with a 50 per cent underdensity. Alternative probes than Kband galaxy surveys have also been used to study this hypothesis.…”