A new method for classifying galaxy SEDs from multiwavelength photometry

We present a new method to classify the broad band optical-NIR spectral energy distributions (SEDs) of galaxies using three shape parameters (super-colours) based on a Principal Component Analysis of model SEDs. As well as providing a compact representation of the wide variety of SED shapes, the method allows for easy visualisation of information loss and biases caused by the incomplete sampling of the rest-frame SED as a function of redshift. We apply the method to galaxies in the UKIDSS Ultra Deep Survey with 0.911, declining steadily to 13% at log(M*/Msol)=10. The properties and mass-function of the post-starburst galaxies are consistent with a scenario in which gas-rich mergers contribute to the growth of the low and intermediate mass range of the red sequence.
Comment: 19 pages, 17 figures, MNRAS accepted. A version with high resolution figures can be downloaded from http://www-star.st-and.ac.uk/~vw8/udsz_supercolour_hires.pdf