Limits on statistical anisotropy from BOSS DR12 galaxies using bipolar spherical harmonics

Understand

We measure statistically anisotropic signatures imprinted in three-dimensional galaxy clustering using bipolar spherical harmonics (BipoSHs) in both Fourier space and configuration space.

• We then constrain a well-known quadrupolar anisotropy parameter $g_{2M}$ in the primordial power spectrum, parametrized by $P(\vec{k}) = \bar{P}(k) [ 1 + \sum_{M} g_{2M} Y_{2M}(\hat{k}) ]$, with $M$ determining the direction of the anisotropy.
• Such an anisotropic signal is easily contaminated by artificial asymmetries due to specific survey geometry.
• We precisely estimate the contaminated signal and finally subtract it from the data.