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arXiv · 2602.04987

The Impact of Galaxy Formation on Galaxy Biasing, and Implications for Primordial non-Gaussianity Constraints

Lucia A. Perez·Shy Genel·Elisabeth Krause·Rachel S. Somerville
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Abstract

The parameter $f_{\textrm{NL}}$ measures the local non-Gaussianity in the primordial energy fluctuations of the Universe, with any deviation from $f_{\textrm{NL}}=0$ providing key constraints on inflationary models. Galaxy clustering is sensitive to $f_{\textrm{NL}}$ at large scale modes and the next generation of galaxy surveys will approach a statistical error of $σ_{f_{\textrm{NL}}}\sim1$. However, the systematic errors on these constraints are dominated by the degeneracy of $f_{\textrm{NL}}$ with the galaxy bias parameters $b_1$ (galaxy overdensities caused by mass perturbations) and $b_ϕ$ (galaxy overdensities caused by primordial potential perturbations). It has been shown that the assumed scaling of $b_ϕ(z)=2δ_c (b_1(z)-1)$ is not accurate for realistically simulated galaxies, and depends both on the galaxy selection and the way that galaxies are modeled. To address this, we leverage the CAMELS-SAM pipeline to explore how varying parameters of galaxy formation affects $b_ϕ$ and $b_1$ for various galaxy selections. We run separate-universe N-body simulations of $L=205 h^{-1}$ cMpc and $N=1280^3$ to measure $b_ϕ$, and run 55 unique instances of the Santa Cruz semi-analytic model with varying parameters of stellar and AGN feedback. We find the behavior and evolution of a SC-SAM model's stellar-, SFR- and sSFR- to halo mass relationships track well with how $b_1$ and $b_ϕ(b_1)$ change across redshift and selection for the SC-SAM. We find our variations of the SC-SAM encapsulate the $b_ϕ$ behavior previously measured in IllustrisTNG, the Munich SAM, and Galacticus.Finally, we identify sSFR selections as particularly robust to varied galaxy modeling.

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Lucia A. Perez, Shy Genel, Elisabeth Krause, Rachel S. Somerville. 2026-02-04. The Impact of Galaxy Formation on Galaxy Biasing, and Implications for Primordial non-Gaussianity Constraints. https://arxiv.org/abs/2602.04987

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