Gravity and Large-Scale Non-local Bias

Abstract

The relationship between galaxy and matter overdensities, bias, is most often assumed to be local. This is however unstable under time evolution, we provide proofs under several sets of assumptions. In the simplest model galaxies are created locally and linearly biased at a single time, and subsequently move with the matter (no velocity bias) conserving their comoving number density (no merging). We show that, after this formation time, the bias becomes unavoidably non-local and non-linear at large scales. We identify the non-local gravitationally induced fields in which the galaxy overdensity can be expanded, showing that they can be constructed out of the invariants of the deformation tensor (Galileons). In addition, we show that this result persists if we include an arbitrary evolution of the comoving number density of tracers. We then include velocity bias, and show that new contributions appear, a dipole field being the signature at second order. We test these predictions by studying the dependence of halo overdensities in cells of fixed matter density: measurements in simulations show that departures from the mean bias relation are strongly correlated with the non-local gravitationally induced fields identified by our formalism. The effects on non-local bias seen in the simulations are most important for the most biased halos, as expected from our predictions. The non-locality seen in the simulations is not fully captured by assuming local bias in Lagrangian space. Accounting for these effects when modeling galaxy bias is essential for correctly describing the dependence on triangle shape of the galaxy bispectrum, and hence constraining cosmological parameters and primordial non-Gaussianity. We show that using our formalism we remove an important systematic in the determination of bias parameters from the galaxy bispectrum, particularly for luminous galaxies. (abridged)

26 pages, 9 figures. v2: improved appendix A

References in corpus (13)

• Transients from Initial Conditions in Cosmological Simulations
• Nonlinear Evolution of Baryon Acoustic Oscillations
• Clustering of dark matter tracers: generalizing bias for the coming era of precision LSS
• Cosmology and the Bispectrum
• The Scale Dependence of Halo and Galaxy Bias: Effects in Real Space
• Generation of Vorticity and Velocity Dispersion by Orbit Crossing
• Nonlinear Perturbation Theory Integrated with Nonlocal Bias, Redshift-space Distortions, and Primordial Non-Gaussianity
• Modeling scale-dependent bias on the baryonic acoustic scale with the statistics of peaks of Gaussian random fields
• Large-scale BAO signatures of the smallest galaxies
• Three-Point Correlation Functions of SDSS Galaxies: Luminosity and Color Dependence in Redshift and Projected Space
• The clustering of radio galaxies at z~0.55 from the 2SLAQ LRG survey
• Modeling the three-point correlation function
• Large-Scale Structure in Brane-Induced Gravity I. Perturbation Theory

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• Halo Sampling, Local Bias and Loop Corrections
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