Authors: Massardi, Marcella; Bonaldi, Anna¹; Negrello, Mattia²; Ricciardi, Sara³; Raccanelli, Alvise⁴; De Zotti, Gianfranco

Source: Monthly Notices of the Royal Astronomical Society, Volume 404, Number 1, May 2010 , pp. 532-544(13)

Publisher: Wiley-Blackwell

Abstract:

We present a new evolutionary model that describes the population properties of radio sources at frequencies ≲5 GHz, thus complementing the De Zotti et al. model, holding at higher frequencies. We find that simple analytic luminosity evolution is still sufficient to fit the wealth of available data on local luminosity functions, multifrequency source counts and redshift distributions. However, the fit requires a luminosity-dependent decline of source luminosities at high redshifts, at least for steep-spectrum sources, thus confirming earlier indications of a `downsizing' also for radio sources. The upturn of source counts at sub-mJy levels is accounted for by a straightforward extrapolation, using the empirical far-infrared (far-IR)/radio correlation, of evolutionary models matching the far-IR counts and redshift distributions of star-forming galaxies. We also discuss the implications of the new model for the interpretation of data on large-scale clustering of radio sources and on the integrated Sachs-Wolfe (ISW) effect, and for the investigation of the contribution of discrete sources to the extragalactic background. As for the ISW effect, a new analysis, exploiting a very clean cosmic microwave background map, yields at a substantially higher significance than reported before.

Keywords: galaxies: active; galaxies: evolution; radio continuum: general

Document Type: Research article

DOI: http://dx.doi.org/10.1111/j.1365-2966.2010.16305.x

Affiliations: 1: INAF, Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, I-35122 Padova, Italy 2: Department of Physics and Astronomy, Open University, Walton Hall, Milton Keynes MK7 6AA 3: INAF/IASF, Sezione di Bologna, Via Gobetti, 101, I-40129 Bologna, Italy 4: Institute of Cosmology & Gravitation, University of Portsmouth, Portsmouth P01 3FX

Publication date: 2010-05-01

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