Luminosity functions for galaxies and quasars in the Spitzer Wide-area Infrared Extragalactic Legacy Survey

Babbedge, T.S.R.; Rowan-Robinson, M.; Vaccari, M.; Surace, J.A.; Lonsdale, C.J.; Clements, D.L.; Fang, F.; Farrah, D.; Franceschini, A.; Gonzalez-Solares, E.; Hatziminaoglou, E.; Lacey, C.G.; Oliver, S.; Onyett, N.; Pérez-Fournon, I.; Polletta, M.; Pozzi, F.; Rodighiero, G.; Shupe, D.L.; Siana, B.; Smith, H.E.

Abstract

We construct rest-frame luminosity functions (LFs) at 3.6, 4.5, 5.8, 8 and 24 μm over the redshift range 0 < z < 2 for galaxies and 0 < z < 4 for optical quasi-stellar objects (QSOs), using optical and infrared (IR) data from the Spitzer Wide-area Infrared Extragalactic (SWIRE) Survey. The 3.6- and 4.5-μm galaxy LFs show evidence for moderate positive luminosity evolution up to z∼ 1.5, consistent with the passive ageing of evolved stellar populations. Their comoving luminosity density was found to evolve passively, gradually increasing out to z∼ 0.5–1 but flattening, or even declining, at higher redshift. Conversely, the 24-μm galaxy LF, which is more sensitive to obscured star formation and/or active galactic nuclei (AGN) activity, undergoes strong positive evolution, with the derived IR energy density and star formation rate (SFR) density ∝ (1 +z)γ with γ= 4.5+0.7−0.6 and the majority of this evolution occurring since z∼ 1. Optical QSOs, however, show positive luminosity evolution in all bands, out to the highest redshifts (3 < z < 4). Modelling as L*∝ (1 +z)γ gave γ= 1.3+0.1−0.1 at 3.6 μm, γ= 1.0+0.1−0.1 at 4.5 μm and stronger evolution at the longer wavelengths (5.8, 8 and 24 μm), of γ∼ 3. Comparison of the galaxy LFs to predictions from a semi-analytic model based on cold dark matter (CDM) indicates that an initial mass function (IMF) skewed towards higher mass star formation in bursts compared to locally be preferred. As a result, the currently inferred massive SFRs in distant submm sources may require substantial downwards revision.

Citation

Babbedge, T., Rowan-Robinson, M., Vaccari, M., Surace, J., Lonsdale, C., Clements, D., …Smith, H. (2006). Luminosity functions for galaxies and quasars in the Spitzer Wide-area Infrared Extragalactic Legacy Survey. Monthly Notices of the Royal Astronomical Society, 370(3), 1159-1180. https://doi.org/10.1111/j.1365-2966.2006.10547.x

• Journal Article Type: Article
• Publication Date: Aug 11, 2006
• Deposit Date: Jun 27, 2014
• Publicly Available Date: Jan 29, 2015
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Royal Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 370
• Issue: 3
• Pages: 1159-1180
• DOI: https://doi.org/10.1111/j.1365-2966.2006.10547.x
• Keywords: Galaxies: evolution, Galaxies: photometry, Quasars: general, Cosmology: observations.
• Public URL: https://durham-repository.worktribe.com/output/1449058