2023/12/22 by Charuhas Shiveshwarkar, Thejs Brinckmann, Shiveshwarkar, Charuhas +3
Earth and Planetary Sciences · Physics and Astronomy · #Cosmology and Gravitation Theories #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #Geophysics and Gravity Measurements
paper · pdf · doi:10.48550/arxiv.2312.15038
openalex publication_date 2023/12/22 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We investigate how well the SPHEREx all-sky survey can constrain local primordial non-Gaussianity beyond the parameter fNL using galaxy power spectra. We forecast joint constraints on the parameters fNL, gNL and τNL obtained assuming a simple two-field curvaton model of inflation. The parameters fNL and gNL characterise the squeezed limits of the primordial bispectrum and trispectrum respectively, and lead to a characteristic scale-dependence of the galaxy bias that increases out to arbitrarily large scales. Values of the parameter τNL> ((6)/(5)fNL)2 cause the galaxy power spectrum to have a stochastic component which also increases out to arbitrarily large scales. Our MCMC forecasts indicate that SPHEREx can provide joint constraints on any two of the three parameters fNL, gNL and τNL. Due to strong degeneracies among these parameters, measurements of the galaxy power spectra alone may not be sufficient to jointly constrain all three. Constraints on fNL, gNL and τNL obtained from galaxy power spectrum observations depend on the modelling of underlying nuisance parameters. We study the robustness of our forecast constraints to modelling choices and note that even with relatively conservative modelling assumptions, SPHEREx galaxy power spectra can provide strong evidence of local non-Gaussianity, even if the particular values of fNL and gNL cannot be measured precisely.