Abstract
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 language | English |
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Number of pages | 17 |
Journal | Monthly Notices of the Royal Astronomical Society |
Volume | 471 |
Issue number | 4 |
DOIs | |
Publication status | Published - 20 Jul 2017 |
Keywords
- dust
- extinction
- galaxies: evolution
- galaxies: high-redshift
- galaxies: luminosity function
- mass function
- galaxies: star formation
- cosmology: observations