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

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