A Constant Clustering Amplitude for Faint Galaxies?

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Abstract
The angular clustering of faint field galaxies is investigated using deep imaging (I~25) obtained with the 10 m Keck I telescope. The autocorrelation function is consistent with ω(θ) ∝ θ−0.8, and although less steep correlation functions cannot be ruled out with high confidence, we find no compelling evidence for a systematic decrease in the power-law index at the faintest magnitude limits. Results from a number of independent observational studies are combined in order to investigate the variation of the correlation amplitude with median I magnitude. At Imed ~ 23, the results obtained by different studies are all in rough agreement and indicate that for Imed > 22 the correlation amplitude declines far less steeply than would be expected from an extrapolation of the trend in the brighter samples. In particular, at Imed ~ 24, our data indicate ω(θ) to be a factor of ~7 higher than the extrapolation. A near independence of magnitude is a general feature of the correlation amplitude in models in which the redshift distribution of the faint field population contains a substantial fraction of galaxies with z 1. In order to reproduce the apparent abrupt flattening of the amplitude of ω(θ) observed at faint limits, approximately 50% of the galaxies in a sample with a depth of I ~ 25 must be at z > 1.
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