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

Abstract

The parameter $f_{\text{NL}}$ measures the local non-Gaussianity in the primordial energy fluctuations of the Universe, with any deviation from $f_{\text{NL}}=0$ providing key constraints on inflationary models. Galaxy clustering is sensitive to $f_{\text{NL}}$ at large scale modes and the next generation of galaxy surveys will approach a statistical error of ${\sigma }_{f_{\text{NL}}}\sim 1$. However, the systematic errors on these constraints are dominated by the degeneracy of $f_{\text{NL}}$ with the galaxy bias parameters $b_1$ (galaxy overdensities caused by mass perturbations) and $b_{\varphi }$ (galaxy overdensities caused by primordial potential perturbations). It has been shown that the assumed scaling of $b_{\varphi }(z)=2{\delta }_c(b_1(z)-1)$ 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 $b_{\varphi }$ and $b_1$ for various galaxy selections. We run separate-universe N-body simulations of $L=205h^{-1}$ cMpc and $N=1280^3$ to measure $b_{\varphi }$, 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 $b_{\varphi }(b_1)$ change across redshift and selection for the SC-SAM. We find our variations of the SC-SAM encapsulate the $b_{\varphi }$ behavior previously measured in IllustrisTNG, the Munich SAM, and Galacticus.Finally, we identify sSFR selections as particularly robust to varied galaxy modeling.

37 pages, 23 figures, 2 tables