Detecting the relativistic galaxy bispectrum

Understand

The Fourier-space galaxy bispectrum is complex, with the imaginary part arising from leading-order relativistic corrections, due to Doppler, gravitational redshift and related line-of-sight effects in redshift space.

• The detection of the imaginary part of the bispectrum is potentially a smoking gun signal of relativistic contributions.
• We investigate whether next-generation spectroscopic surveys could make such a detection.
• For a Stage IV spectroscopic $H\alpha$ survey similar to Euclid, we find that the cumulative signal to noise of this relativistic signature is $\mathcal{O}(10)$.