Modest set of simulations of local-type primordial non-Gaussianity in the DESI era
Boryana Hadzhiyska, Lehman H. Garrison, Daniel J. Eisenstein, Simone Ferraro
Abstract
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 abacuspng set presented in this study, consisting of 9 boxes, each of size ${L}_{\mathrm{box}}=2\text{ }\text{ }\mathrm{Gpc}/h$ and particle mass of $1.01\ifmmode\times\else\texttimes\fi{}{10}^{10}{M}_{\ensuremath{\bigodot}}/h$, provide a viable path forward. As validation, we find good agreement between the simulations and our expectations from one-loop perturbation theory (PT) and the ``separate universe'' method for the matter bispectrum, matter power spectrum and the halo bias parameter associated with PNG, ${b}_{\ensuremath{\phi}}$. As a science application, we investigate the link between halo assembly bias and ${b}_{\ensuremath{\phi}}$ 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 ${b}_{\ensuremath{\phi}}$ and the assembly history of halos needs to be taken into account by future PNG analyses. We further perform the first study of the ${b}_{\ensuremath{\phi}}$ parameter from fits to early DESI data of the luminous red galaxy (LRG) and quasistellar object (QSO) samples and comment on the effect on ${f}_{\mathrm{NL}}$ constraints for the allowed galaxy-halo models (note that $\ensuremath{\sigma}[{f}_{\mathrm{NL}}]\ensuremath{\propto}\frac{\ensuremath{\sigma}[{b}_{\ensuremath{\phi}}]}{{b}_{\ensuremath{\phi}}}$). We find that the error on ${f}_{\mathrm{NL}}$ is 15, 8, 7 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.