A new method for classifying galaxy SEDs from multiwavelength photometry

Vivienne Wild, Omar Almaini, Michele Cirasuolo, Jim Dunlop, Ross McLure, Rebecca Bowler, Joao Ferreira, Emma Bradshaw, Robert Chuter, Will Hartley

Research output: Contribution to journalArticlepeer-review

40 Citations (Scopus)


We present a new method to classify the broad-band optical–near-infrared 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 visualization 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 United Kingdom Infrared Telescope Infrared Deep Sky Survey Ultra Deep Survey with 0.9 < z < 1.2, and confirm our classifications by stacking rest-frame optical spectra for a fraction of objects in each class. As well as cleanly separating a tight red sequence from star-forming galaxies, three unusual populations are identifiable by their unique colours: very dusty star-forming galaxies with high metallicity and old mean stellar age; post-starburst galaxies which have formed ≳10 per cent of their mass in a recent unsustained starburst event; and metal-poor quiescent dwarf galaxies. We find that quiescent galaxies account for 45 per cent of galaxies with log M*/M > 11, declining steadily to 13 per cent at log M*/M = 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.

Original languageEnglish
Pages (from-to)1880-1898
Number of pages19
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
Early online date28 Mar 2014
Publication statusPublished - 11 May 2014


  • Methods: statistical
  • Galaxies: fundamental parameters
  • Galaxies: luminosity function
  • Mass function
  • Galaxies: photometry
  • Galaxies: statistics
  • Galaxies: stellar content


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