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

• Published in: Monthly notices of the Royal Astronomical Society 2014-08, Vol.442 (3), p.2511-2518
• Main Authors: Ferramacho, L. D., Santos, M. G., Jarvis, M. J., Camera, S.
• Format: Article
• Language: English
• Subjects: Accuracy; Arrays; Bias; Cosmic microwave background; Cosmic microwave background temperature; Flux; Matrix; Populations; Quasars; Radio galaxies; Star & galaxy formation; Surveys; Symbols
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stu1015

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 σ f nl = 3.6 on the local non-Gaussian parameter for a galaxy detection flux limit of 10 μJy and σ f nl = 2.2 for 1 μJy. We show that this significantly improves on the constraints obtained when using the whole undifferentiated populations (σ f nl = 48 10 μJy and σ f nl = 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 σ f nl ∼ 1 with the Square Kilometre Array.