A comparison of HzRG source counts with the reference SWIRE fields. The distribution of the SWIRE 24 μm  source counts in  ~ 10 000 cirular cells of 1.75′ radius, representing five SWIRE fields, is plotted as a grey histogram. A Gaussian fit to the lower part of this distribution is overlayed as a dashed line. A 3σ above the SWIRE mean is indicated as a dot-dash line. A histogram of HzRG field densities is overlayed along with each HzRG name. The corresponding source number density is indicated on the right axis.