The Canada-France deep fields survey -: II:: Lyman-break galaxies and galaxy clustering at z ∼ 3

We present a large sample of z similar to 3 U-band dropout galaxies extracted from the Canada-France deep fields survey (CFDF). Our catalogue covers an effective area of similar to1700 arcmin(2) divided between three large, contiguous fields separated widely on the sky. To I-AB = 24.5, the survey contains 1294 Lyman-break candidates, in agreement with previous measurements by other authors, after appropriate incompleteness corrections have been applied to our data. Based on comparisons with spectroscopic observations and simulations, we estimate that our sample of Lyman-break galaxies is contaminated by stars and interlopers (lower-redshift galaxies) at no more than similar to30%. We find that omega(theta) is well fitted by a power-law of fixed slope, gamma = 1.8, even at small (theta < 10") angular separations. In two of our three fields, we are able to fit simultaneously for both the slope and amplitude and find gamma = 1.8 +/- 0.2 and r(0) = (5.3(-2.2)(+6.8))h(-1) Mpc, and gamma = 1.8 +/- 0.3 and r(0) = (6.3(-2.8)(+17.9))h(-1) Mpc (all spatially dependent quantities are quoted for a Lambda-flat cosmology). Our data marginally indicates in one field (at a 3sigma level) that the Lyman-break correlation length r(0) depends on sample limiting magnitude: brighter Lyman-break galaxies are more clustered than fainter ones. For the entire CFDF sample, assuming a fixed slope gamma = 1.8 we find r(0) = (5.9 +/- 0.5)h(-1) Mpc. Using these clustering measurements and prediction for the dark matter density field computed assuming cluster-normalised linear theory, we derive a linear bias of b = 3.5 +/- 0.3. Finally we show that the dependence of the correlation length with the surface density of Lyman-break galaxies is in good agreement with a simple picture where more luminous galaxies are hosted by more massive dark matter halos with a simple one-to-one correspondence.