The evolving far-IR galaxy luminosity function and dust-obscured star formation rate density out to z≃5.

M. P. Koprowski, J. S. Dunlop, M. J. Michałowski, K. E. K. Coppin, J. E. Geach, R. J. McLure, D Scott, P. P. van der Werf

Research output: Contribution to journalArticlepeer-review


We present a new measurement of the evolving galaxy far-IR luminosity function (LF) extending out to redshifts z ≃ 5, with resulting implications for the level of dust-obscured star formation density in the young Universe. To achieve this, we have exploited recent advances in sub-mm/mm imaging with SCUBA-2 on the James Clerk Maxwell Telescope and the Atacama Large Millimeter/Submillimeter Array, which together provide unconfused imaging with sufficient dynamic range to provide meaningful coverage of the luminosity-redshift plane out to z > 4. Our results support previous indications that the faint-end slope of the far-IR LF is sufficiently flat that comoving luminosity density is dominated by bright objects (≃L*). However, we find that the number density/luminosity of such sources at high redshifts has been severely overestimated by studies that have attempted to push the highly confused Herschel SPIRE surveys beyond z ≃ 2. Consequently, we confirm recent reports that cosmic star formation density is dominated by UV-visible star formation at z > 4. Using both direct (1/Vmax) and maximum likelihood determinations of the LF, we find that its high-redshift evolution is well characterized by continued positive luminosity evolution coupled with negative density evolution (with increasing redshift). This explains why bright sub-mm sources continue to be found at z > 5, even though their integrated contribution to cosmic star formation density at such early times is very small. The evolution of the far-IR galaxy LF thus appears similar in form to that already established for active galactic nuclei, possibly reflecting a similar dependence on the growth of galaxy mass.
Original languageEnglish
Number of pages17
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
Publication statusPublished - 20 Jul 2017


  • dust
  • extinction
  • galaxies: evolution
  • galaxies: high-redshift
  • galaxies: luminosity function
  • mass function
  • galaxies: star formation
  • cosmology: observations


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