How I stop worrying about non-universality and $b_{\varphi }$: Constraining local $f_{\mathrm{NL}}$ with $b_{\varphi }$ priors from HOD posteriors

Abstract

Local primordial non-Gaussianity (local PNG) induces a scale-dependent contribution to galaxy clustering proportional to $f_{\mathrm{NL}}{b}_{\varphi }$, where $f_{\mathrm{NL}}$ is the local PNG amplitude and $b_{\varphi }$ encodes the galaxy response to a long-wavelength primordial potential perturbation. Uncertainty in $b_{\varphi }$ is the dominant obstacle to precise, robust constraints on $f_{\mathrm{NL}}$ from galaxy surveys. We translate small-scale clustering constraints on the galaxy--halo connection into priors on $b_{\varphi }$: sampling the posterior of a halo occupation distribution (HOD) model fit to the DESI EDR, we generate mocks from which we measure $b_{\varphi }$ and construct its prior. Validating against additional mocks with different local PNG amplitudes, we show that the method recovers unbiased $f_{\mathrm{NL}}$, even in the presence of assembly bias.

9+3 pages, 3 figures, 7 tables, no worries. Code is available at: https://github.com/MinhMPA/bphi-prior-from-hod-posterior