Multitracer technique for galaxy bispectrum: An application to constraints on nonlocal primordial non-Gaussianities

摘要

We explore the use of galaxy bispectra with the multitracer technique as a possible probe of primordial non-Gaussianities. We forecast future constraints on non-linearity parameters, f_(NL)~(eq) and f_(NL)~(orth) , which, respectively, characterize the equilateral- and orthogonal-type primordial bispectra, and show that the multitracer analysis would be effective with reducing the cosmic-variance noise if the number density of galaxies is high enough. We find that the measurement of the galaxy bispectrum by future galaxy surveys can reach the constraints on the nonlocal-type primordial non-Gaussianities to the level more severe than current one which has been obtained by cosmic microwave background observations.