Radio galaxy populations and the multitracer technique: pushing the limits on primordial non-Gaussianity

Journal article

We explore the use of different radio galaxy populations as tracers of different mass haloes and therefore, with different bias properties, to constrain primordial non-Gaussianity of the local type.We perform a Fisher matrix analysis based on the predicted auto- and cross-angular power spectra of these populations, using simulated redshift distributions as a function of detection flux and the evolution of the bias for the different galaxy types (star-forming galaxies, starburst galaxies, radio-quiet quasars, FR I and FR II AGN galaxies). We show that such a multitracer analysis greatly improves the information on non-Gaussianity by drastically reducing the cosmic variance contribution to the overall error budget. By applying this method to future surveys, we predict a constraint of σfnl = 3.6 on the local non-Gaussian parameter for a galaxy detection flux limit of 10 μJy and σfnl = 2.2 for 1 μJy.We show that this significantly improves on the constraints obtained when using the whole undifferentiated populations (σfnl = 48 for 10 μJy and σfnl = 12 for 1 μJy). We conclude that continuum radio surveys alone have the potential to constrain primordial non-Gaussianity to an accuracy at least a factor of 2 better than the present constraints obtained with Planck data on the cosmic microwave background bispectrum, opening a window to obtain σfnl ~ 1 with the Square Kilometre Array. © 2014 The Authors.

Authors: Ferramacho, L; Santos, MG; Jarvis, M; Camera, S

• Publication status: Published
• Publisher: Oxford University Press
• Journal: Monthly Notices of the Royal Astronomical Society
• Volume: 442
• Issue: 3
• Pages: 2511-2518
• Publication date: 2014-08-11
• DOI: 10.1093/mnras/stu1015
• EISSN: 1365-2966
• ISSN: 0035-8711
• Language: English
• Keywords: inflation; radio continuum: galaxies; cosmology: observations; cosmological parameters; large-scale structure of Universe