The Impact of Spectroscopic Fibre Collisions on the Observed Angular Correlation Function

Abstract

The design of some spectroscopic galaxy surveys is such that fibre collisions can affect the completeness of the survey. To quantify this effect, we compare the two-point correlation functions, $\omega(\theta)$, of two surveys with differing observational strategies. Fibre collisions are an accepted consequence of the design of the Sloan Digital Sky Survey's spectroscopic campaign (SDSS), whereas the Galaxy And Mass Assembly survey (GAMA) circumvents fibre-collisions by re-observing fields using different fibre configurations. We show that the correlation functions of these surveys diverge at scales smaller than the SDSS fibre collision limit, and that at separations smaller than $20''$ $\omega(\theta)_{\text{GAMA}} > \omega(\theta)_{\text{SDSS}}$ with $>4\sigma$ confidence.