The average detection limit of our deep NACO image taken in the K_s-band in September 2009 plotted for a range of angular (bottom) and projected separation (top). The detection limit achieved in this image is shown as a dotted line, as well as the detection limit after PSF subtraction (solid line). Because of saturation, objects within a separation of 3 NACO pixels (or 40 mas of angular separation) cannot be detected around the bright primary. The position of PZ Tel B is indicated as black circle. Dashed horizontal lines show the expected brightness of substellar objects, whose masses are listed at the right side of the plot.