Speaker: Roy Maartens (Western Cape U.)
Title: The dipole of the galaxy bispectrum
Abstract:
The imaginary part of the galaxy bispectrum at leading order is a unique relativistic signal that can be extracted from the full bispectrum. In Fourier space, this Doppler-type signal scales as iH/k. The galaxy power spectrum for a single tracer includes only the squared contribution, scaling as (H/k)^2, which is highly suppressed and not detectable. By contrast, in the bispectrum of a single tracer, the iH/k relativistic signal survives because it couples with the Newtonian terms - thus increasing the chances of detection. We show that the SNR forecast for a Stage IV H-alpha galaxy spectroscopic survey is ~20. For next-generation 21cm intensity mapping surveys, the signal is also in principle detectable, but at lower significance.