Optimal Multiwavelength Source Detection: Experience Gained from the WISE Mission

We discuss the optimal detection of point sources from multiwavelength imaging data using an approach, referred to as MDET, which requires no prior knowledge of the source spectrum. MDET may be regarded as a somewhat more general version of the so-called `chi-squared' technique. We describe the theoretical basis of the technique, and show examples of its performance with four-channel infrared broad-band imaging data from the WISE mission. We also discuss the potential benefits of applying it to the multifrequency data cubes of the ASKAP surveys, and suggest that it could increase the detection sensitivity of searches for neutral hydrogen emission at moderately high redshifts.