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

August 2006 • 2006MNRAS.370.1159B

Authors • 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 3.6μm,γ = 1.0^+0.1_-0.1 at 4.5μm and stronger evolution at the longer wavelengths (5.8, 8 and 24μm), 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.

Links

• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2006MNRAS.370.1159B
• PDF https://academic.oup.com/mnras/pdf-lookup/doi/10.1111/j.1365-2966.2006.10547.x
• PREPRINT http://arxiv.org/abs/astro-ph/0605305
• DATA https://irsa.ipac.caltech.edu/bibdata/2006/B/2006MNRAS.370.1159B.html
• ELECTR http://dx.doi.org/10.1111/j.1365-2966.2006.10547.x
• GIF http://articles.adsabs.harvard.edu/full/2006MNRAS.370.1159B
• ARTICLE http://articles.adsabs.harvard.edu/full/2006MNRAS.370.1159B?defaultprint=YES
• SPIRES http://inspirehep.net/search?p=find+eprint+astro-ph/0605305