Modelling nearest neighbour distributions of biased tracers using hybrid effective field theory
Abstract
We investigate the application of hybrid effective field theory (HEFT) - which combines a Lagrangian bias expansion with subsequent particle dynamics from N-body simulations - to the modelling of k-nearest neighbour cumulative distribution functions (kNN-CDFs) of biased tracers of the cosmological matter field. The kNN-CDFs are sensitive to all higher order connected N-point functions in the data, but are computationally cheap to compute. We develop the formalism to predict the kNN-CDFs of discrete tracers of a continuous field from the statistics of the continuous field itself. Using this formalism, we demonstrate how kNN-CDF statistics of a set of biased tracers, such as haloes or galaxies, of the cosmological matter field can be modelled given a set of low-redshift HEFT component fields and bias parameter values. These are the same ingredients needed to predict the two-point clustering. For a specific sample of haloes, we show that both the two-point clustering and the kNN-CDFs can be well-fit on quasi-linear scales (≳ 20h-1Mpc) by the second-order HEFT formalism with the same values of the bias parameters, implying that joint modelling of the two is possible. Finally, using a Fisher matrix analysis, we show that including kNN-CDF measurements over the range of allowed scales in the HEFT framework can improve the constraints on σ8 by roughly a factor of 3, compared to the case where only two-point measurements are considered. Combining the statistical power of kNN measurements with the modelling power of HEFT, therefore, represents an exciting prospect for extracting greater information from small-scale cosmological clustering.
- Publication:
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Monthly Notices of the Royal Astronomical Society
- Pub Date:
- April 2022
- DOI:
- 10.1093/mnras/stac193
- arXiv:
- arXiv:2107.10287
- Bibcode:
- 2022MNRAS.511.2765B
- Keywords:
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- cosmological parameters;
- large-scale structure of Universe;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- Accepted to MNRAS. Matches accepted version