Statistics of biased tracers in variance-suppressed simulations

Abstract

Cosmological simulations play an increasingly important role in analysing the observed large-scale structure of the Universe. Recently, they have been particularly important in building hybrid models that combine a perturbative bias expansion with displacement fields extracted from N-body simulations to describe the clustering of biased tracers. Here, we show that simulations that employ a technique referred to as “Fixing-and-pairing” (F&P) can dramatically improve the statistical precision of such hybrid models. Specifically, by numerical and analytical means, we show that F&P simulations provide unbiased estimates for all statistics employed by hybrid models while reducing, by up to two orders of magnitude, their uncertainty on large scales. This roughly implies that an EUCLID-like survey could be analysed using simulations of 2 Gpc a side — a 20% of the survey volume. Our work establishes the robustness of F&P for current hybrid theoretical models for galaxy clustering, an important step towards achieving an optimal exploitation of large-scale structure measurements.

The effective field theory of large-scale structure and multi-tracer

“…The simulations were performed with the paired & fixed method of [60], which strongly suppresses the cosmic variance. That allow us to reescale the volume of the sample by adjusting the covariance [61]. Since the simulation volume is…”

“…Notice that, since the simulations described in Sec. 3.1 were performed with the paired & fixed method [60], we can (artifitially) reescale the volume V s of the sample considered in the covariance [61].…”

“…3, the simulation was performed using the paired & fixed method of [60], which substantially suppresses the cosmic variance. It allow us to safely rescale the sample volume, V s ≈ 3 [Gpc/h] 3 , to higher values by simply adjusting the covariance (3.7) [61]. On the right panel of Fig.…”

The effective field theory of large-scale structure and multi-tracer II: redshift space and realistic tracers

“…The simulations were performed with the paired & fixed method of [60], which strongly suppresses the cosmic variance. That allow us to rescale the volume of the sample by adjusting the covariance [61]. Since the simulation volume is V BOSS ∼ 6 [Gpc/h] 3 (see e.g.…”

“…Notice that, since the simulations described in section 3.1 were performed with the paired & fixed method [60], we can (artifitially) rescale the volume V s of the sample considered in the covariance [61].…”