Geometrical compression: a new method to enhance the BOSS galaxy bispectrum monopole constraints
Abstract
We present a novel method to compress galaxy clustering threepoint statistics and apply it to redshift space galaxy bispectrum monopole measurements from BOSS DR12 CMASS data considering a kspace range of 0.030.12 h/Mpc. The method consists in binning together bispectra evaluated at sets of wavenumbers forming closed triangles with similar geometrical properties: the area, the cosine of the largest angle, and the ratio between the cosines of the remaining two angles. This enables us to increase the number of bispectrum measurements, for example by a factor of 23 over the standard binning (from 116 to 2734 triangles used), which is otherwise limited by the number of mock catalogues available to estimate the covariance matrix needed to derive parameter constraints. The 68{{ per cent}} credible intervals for the inferred parameters (b_{1}, b_{2}, f, σ_{8}) are thus reduced by \left(39{{ per cent}},49{{ per cent}},29{{ per cent}},22{{ per cent}}\right), respectively. We find very good agreement with the posteriors recently obtained by alternative maximal compression methods. This new method does not require the apriori computation of the data vector covariance matrix and has the potential to be directly applicable to other threepoint statistics (e.g. galaxy clustering, weak gravitational lensing, 21cm emission line) measured from future surveys such as DESI, Euclid, PFS, and SKA.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 March 2019
 DOI:
 10.1093/mnrasl/sly242
 arXiv:
 arXiv:1901.00987
 Bibcode:
 2019MNRAS.484L..29G
 Keywords:

 methods: analytical;
 methods: data analysis;
 methods: statistical;
 cosmology: cosmological parameters;
 cosmology: largescale structure of Universe;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 5 pages, 2 figures, Accepted by MNRAS: Letters