A semi-empirical simulation of the extragalactic radio continuum sky for next generation radio telescopes

• Published in: Monthly notices of the Royal Astronomical Society Vol. 388; no. 3; pp. 1335 - 1348
• Main Authors: Wilman, R. J., Miller, L., Jarvis, M. J., Mauch, T., Levrier, F., Abdalla, F. B., Rawlings, S., Klöckner, H.-R., Obreschkow, D., Olteanu, D., Young, S.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 11-08-2008; Blackwell Science; Oxford University Press
• Subjects: Astronomy; Astrophysics; Cosmology; Dark matter; Earth, ocean, space; Exact sciences and technology; galaxies: active; galaxies: luminosity function; galaxies: luminosity function, mass function; galaxies: starburst; large-scale structure of Universe; mass function; Radio astronomy; radio continuum: galaxies; Simulation; galaxies: starburst; galaxies: luminosity function, mass function; galaxies: active; large-scale structure of Universe; radio continuum: galaxies; Cosmological redshift; Starburst galaxies; Radiowave interferometers; Large-scale structure; Continuum; Active galaxy nuclei; Galaxy nuclei; Internal structure; Cosmic radio sources; Radio galaxies; Hot spots; Galaxy clusters; Active galaxies; Point sources; Upper bound; Flux density; Mass function; Dark matter; Astronomical catalogues; Models; Luminosity function
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1111/j.1365-2966.2008.13486.x

We have developed a semi-empirical simulation of the extragalactic radio continuum sky suitable for aiding the design of next generation radio interferometers such as the Square Kilometre Array (SKA). The emphasis is on modelling the large-scale cosmological distribution of radio sources rather than the internal structure of individual galaxies. Here we provide a description of the simulation to accompany the online release of a catalogue of ≃320 million simulated radio sources. The simulation covers a sky area of 20 × 20 deg2- a plausible upper limit to the instantaneous field of view attainable with future (e.g. SKA) aperture array technologies - out to a cosmological redshift of z= 20, and down to flux density limits of 10 nJy at 151, 610 MHz, 1.4, 4.86 and 18 GHz. Five distinct source types are included: radio-quiet active galactic nuclei (AGN), radio-loud AGN of the Fanaroff-Riley type I (FR I) and FR II structural classes, and star-forming galaxies, the latter split into populations of quiescent and starbursting galaxies.
In our semi-empirical approach, the simulated sources are drawn from observed (or extrapolated) luminosity functions and grafted on to an underlying dark matter density field with biases which reflect their measured large-scale clustering. A numerical Press-Schechter style filtering of the density field is used to identify and populate clusters of galaxies. For economy of output, radio source structures are constructed from point source and elliptical subcomponents, and for FR I and FR II sources an orientation-based unification and beaming model is used to partition flux between the core and extended lobes and hotspots. The extensive simulation output gives users the flexibility to post-process the catalogues to achieve more complete agreement with observational data in the years ahead. The ultimate aim is for the 'idealized skies' generated by this simulation and associated post-processing to be fed to telescope simulators to optimize the design of the SKA itself.