Limits on statistical anisotropy from BOSS DR12 galaxies using bipolar spherical harmonics
Abstract
We measure statistically anisotropic signatures imprinted in threedimensional galaxy clustering using bipolar spherical harmonics in both Fourier space and configuration space. We then constrain a wellknown quadrupolar anisotropy parameter g_{2M} in the primordial power spectrum, parametrized by P(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. Using the galaxy samples obtained by the Baryon Oscillation Spectroscopic Survey Data Release 12, we find no evidence for violation of statistical isotropy, g_{2M} for all M to be of zero within the 2σ level. The g_{2M}type anisotropy can originate from the primordial curvature power spectrum involving a directionaldependent modulation g_* (\hat{k} \cdot \hat{p})^2. The bound on g_{2M} is translated into g_{*} as 0.09 < g_{*} < 0.08 with a 95 per cent confidence level when \hat{p} is marginalized over.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 January 2018
 DOI:
 10.1093/mnras/stx2333
 arXiv:
 arXiv:1704.02868
 Bibcode:
 2018MNRAS.473.2737S
 Keywords:

 dark matter;
 largescale structure of Universe;
 cosmology: observations;
 cosmology: theory;
 Astrophysics  Cosmology and Nongalactic Astrophysics;
 Astrophysics  Astrophysics of Galaxies;
 General Relativity and Quantum Cosmology
 EPrint:
 17 pages, 6 figures, accepted for publication in MNRAS