2004/07/23 by I. Prandoni, Prandoni, I., H. R. de Ruiter +3
Physics and Astronomy · #Astrophysics (astro-ph) #Astrophysics and Cosmic Phenomena #FOS: Physical sciences #Radio Astronomy Observations and Technology #Superconducting and THz Device Technology #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/0407499
2 pages, 1 figure. To appear in "Exploring the Cosmic Frontier: Astrophysical Instruments for the 21st Century", proceedings of the conference held in Berlin, 18-21 May 2004
arxiv created 2004/07/23 · openalex publication_date 2004/07/23 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The apparent change in the composition of the parent optical objects of radio sources around 1 mJy (at 1.4 GHz) is now well established, although there is still some debate about the relative importance of classical radio galaxies and star-forming galaxies at sub-mJy levels (see e.g. Gruppioni et al. 1999; Prandoni et al. 2001b). It is clear, however, that at microJy levels star-forming galaxies are dominant (see Fomalont et al. 1997; Haarsma et al. 2000). Does this mean that SKA will basically tell us more about the history of star formation than about the space density (and its cosmological evolution) of active galactic nuclei? Using current best estimates of luminosity functions (and their evolution) of various classes of objects, we show that the increasing dominance of star-forming galaxies below 1 mJy is a natural consequence of the different luminosity functions, but that this does not at all mean that star-forming galaxies do necessarily dominate at all sub-mJy flux levels and all redshifts.