How I stop worrying about non-universality and b phi: Constraining local f NL with b phi priors from HOD posteriors
Jiaxi Yu, Nhat-Minh Nguyen
astro-ph.CO
Submitted: 2026-07-01
Comments: 9+3 pages, 3 figures, 7 tables, no worries. Code is available at: https://github.com/MinhMPA/bphi-prior-from-hod-posterior
Code: https://github.com/MinhMPA/bphi-prior-from-hod-posterior
License: http://creativecommons.org/licenses/by/4.0/
The gist: Local primordial non-Gaussianity (local PNG) induces a scale-dependent contribution to galaxy clustering proportional to f NL,b phi, where f NL is the local PNG amplitude and b phi encodes the galaxy
Terminology
Abstract
Local primordial non-Gaussianity (local PNG) induces a scale-dependent contribution to galaxy clustering proportional to f NL,b phi, where f NL is the local PNG amplitude and b phi encodes the galaxy response to a long-wavelength primordial potential perturbation. Uncertainty in b phi is the dominant obstacle to precise, robust constraints on f NL from galaxy surveys. We translate small-scale clustering constraints on the galaxy--halo connection into priors on b phi: sampling the posterior of a halo occupation distribution (HOD) model fit to the DESI EDR, we generate mocks from which we measure b phi and construct its prior. Validating against additional mocks with different local PNG amplitudes, we show that the method recovers unbiased f NL, even in the presence of assembly bias.
Sources
- Planck 2018 results. IX. Constraints on primordial non-Gaussianity
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