AbacusPNG: A modest set of simulations of local-type primordial non-Gaussianity in the DESI era

A measurement of a primordial non-Gaussianity (PNG) signal through late- or early-Universe probes has the potential to transform our understanding of the physics of the primordial Universe. While large-scale structure observables in principle contain vital information, interpreting these measurements is challenging due to poorly understood astrophysical effects. Luckily, N-body simulations, such as the public {AbacusPNG} set presented in this study, consisting of 9 boxes, each of size Lbox = 2~ Gpc/h and particle mass of 1.01 × 10¹⁰ \ M_/h, provide a viable path forward. As validation, we find good agreement between the simulations and our expectations from one-loop perturbation theory and the `separate universe' method for the matter bispectrum, matter power spectrum and the halo bias parameter associated with PNG, b_φ. As a science application, we investigate the link between halo assembly bias and b_φ for halo properties known to play a vital role in accurately predicting galaxy clustering: concentration, shear (environment), and accretion rate. We find a strong response for all three parameters, suggesting that the connection between b_φ and the assembly history of halos needs to be taken into account by future PNG analyses. We further perform the first study of the b_φ parameter from fits to early DESI data of the luminous red galaxy (LRG) and quasi-stellar object (QSO) samples and comment on the effect on fNL constraints for the allowed galaxy-halo models (note that σ [fNL] ∝ σ [b_φ]/b_φ). We find that the error on fNL is 21, 6, 22 for the LRGs at $z = 0.5$ and $z = 0.8$ and QSOs at $z = 1.4$, respectively, suggesting that a thorough understanding of galaxy assembly bias is warranted so as to perform robust high-precision analysis of local-type PNG with future surveys.