We show that the redshift-space quadrupole will be a powerful tool for constraining dark energy even if the baryon oscillations are missing from the usual monopole power spectrum and bias is scale- and time-dependent .
We calculate the accuracy with which a next-generation galaxy survey based on KAOS will measure the quadrupole power spectrum , which gives the leading anisotropies in the power spectrum in redshift space due to the linear velocity , Finger of God and Alcock-Paczynski effects .
Combining the monopole and quadrupole power spectra breaks the degeneracies between the multiple bias parameters and dark energy both in the linear and nonlinear regimes and , in the complete absence of baryon oscillations ( \Omega _ { b } = 0 ) , leads to a roughly 500 % improvement in constraints on dark energy compared with those from the monopole spectrum alone .
As a result the worst case – with no baryon oscillations – has dark energy errors only mildly degraded relative to the ideal case , providing insurance on the robustness of next-generation galaxy survey constraints on dark energy .