The Canada-France deep fields survey - I. 100 000 galaxies, 1 deg$^\mathsf{2}$: A precise measurement of $\mathsf{\omega(\theta)}$ to $I{_{AB}\sim25}$

received; accepted Abstract. Using the University of Hawaii's 8K mosaic camera (UH8K), we have measured the angular correlation function ω(θ) for 100,000 galaxies distributed over four widely separated fields totalling � 1deg 2 and reaching a limiting magnitude of IAB(3σ,3 '' ) � 25.5. This unique combination of areal coverage and depth allows us to investigate the dependence of ω(θ) at 1 ' , Aω(1 ' ), on sample median magnitude in the range 19.5 < IAB−med < 24. Furthermore, our rigorous control of systematic photometric and astrometric errors means that fainter than IAB−med � 22 we measure ω(θ) on scales of several arc-minutes to an accuracy of 30%. Our results show that Aω(1 ' ) decreases monotonically to IAB � 25. At bright magnitudes, ω(θ) is consistent with a power-law of slope δ = 0.8 for 0.2 ' < θ < 3.0 ' but at fainter magnitudes we detect a slope flattening with δ � 0.6. At the 3σ level, our observations are still consistent with δ = 0.8. We also find a clear dependence of Aω(1 ' ) on observed (V I)AB colour. In the magnitude ranges 18.5 < IAB < 24.0 and 18.5 < IAB < 23.0 we find galaxies with 2.6 < (V I)AB < 2.9 (the reddest bin we consider) have Aω(1 ' )'s which are � 10× higher than the full field population. On the basis of their similar colours and clustering properties, we tentatively identify these objects as a superset of the "extremely red objects" found through optical-infrared selection. We demonstrate that our model predictions for the redshift distribution for the faint galaxy population are in good agreement with current spectroscopic observations. Using these predictions, we find that for low- cosmologies and assuming a local galaxy correlation length r0 = 4.3h −1 Mpc, in the range 19.5 < IAB−med < 22, the growth of galaxy clustering (parameterised by ǫ), is ǫ � 0. However, at 22 < IAB−med < 24.0, our observations are consistent with ǫ & 1. Models with ǫ � 0 cannot simultaneously match both bright and faint measurements of Aω(1 ' ). We show how this result is a natural consequence of the "bias-free" nature of the "ǫ" formalism and is consistent with the field galaxy population in the range 22.0 < IAB < 24.0 being dominated by galaxies of low intrinsic luminosity.