Cosmic star formation probed via parametric stack-fitting of known sources to radio imaging

Abstract

The promise of multiwavelength astronomy has been tempered by the large disparity in sensitivity and resolution between different wavelength regimes. Here, we present a statistical approach which attempts to overcome this by fitting parametric models directly to image data. Specifically, we fit a model for the radio luminosity function (LF) of star-forming galaxies to pixel intensity distributions at 1.4 GHz coincident with near-IR selected sources in COSMOS. Taking a mass-limited sample in redshift bins across the range 0 < z < 4, we are able to fit the radio LF with ̃0.2 dex precision in the key parameters (e.g. φ*,L*). Good agreement is seen between our results and those using standard methods at radio and other wavelengths. Integrating our LFs to get the star formation rate density, we find that galaxies with M* > 109.5 M⊙ contribute ≳50 per cent of cosmic star formation at 0 < z < 4. The scalability of our approach is empirically estimated, with the precision in LF parameter estimates found to scale with the number of sources in the stack, Ns, as α √ Ns. This type of approach will be invaluable in the multiwavelength analysis of upcoming surveys with the Square Kilometre Array pathfinder facilities: LOFAR, ASKAP and MeerKAT. © 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.