Herschel-ATLAS: The angular correlation function of submillimetre galaxies at high and low redshift

We present measurements of the angular correlation function of galaxies selected from the first field of the H-ATLAS survey. Careful removal of the background from galactic cirrus is essential, and currently dominates the uncertainty in our measurements. For our 250 mu m-selected sample we detect no significant clustering, consistent with the expectation that the 250 mu m-selected sources are mostly normal galaxies at z <= 1. For our 350 mu m and 500 mu m-selected samples we detect relatively strong clustering with correlation amplitudes A of 0.2 and 1.2 at 1', but with relatively large uncertainties. For samples which preferentially select high redshift galaxies at z similar to 2-3 we detect significant strong clustering, leading to an estimate of r(0) similar to 7-11 h(-1) Mpc. The slope of our clustering measurements is very steep, delta similar to 2. The measurements are consistent with the idea that sub-mm sources consist of a low redshift population of normal galaxies and a high redshift population of highly clustered star-bursting galaxies.