Assembly bias and local Primordial non-Gaussianity from DESI DR1 Quasars

TL;DR

This paper uses DESI DR1 quasar clustering data and hydrodynamical simulations to constrain primordial non-Gaussianity, accounting for assembly bias effects, resulting in an updated $f_{NL}$ estimate.

Contribution

It provides a robust prior for the assembly bias parameter using simulations, improving constraints on local PNG from quasar clustering data.

Findings

Derived a stable prior for assembly bias parameter p.

Constrained $f_{NL}$ to -3.3 ± 9.2 from DESI DR1 data.

Demonstrated robustness of prior against astrophysical assumptions.

Abstract

The analysis of the large-scale clustering of quasars (QSO) observed by the Dark Energy Spectroscopic Instrument (DESI) represents a promising avenue for constraining local Primordial non-Gaussianity (PNG), parameterized by $f_{\rm NL}$. The signal to be constrained is the scale-dependent bias induced in the 2-point clustering of the considered tracer sample. The resulting constraints on $f_{\rm NL}$, however, are fully degenerate with the local PNG bias parameter $b_{\phi}$, dependent on the assembly bias parameter $p$. Using IllustrisTNG hydrodynamical simulations, we select a QSO sample reflecting the selection criteria and properties of DESI QSOs, and provide a robust prior for $p$, and thus for $b_{\phi}$, building on the findings of Fondi et al. 2024. We find a distribution with mean $\bar{p}\simeq1.4$ with weak redshift dependence, stable to selection noise and consistent with the expected recent merger history typical of quasar-hosting halos. By comparing with the CAMELS simulations we demonstrate that this prior is robust to astrophysical assumptions and cosmic variance. Finally, applying this prior to the DESI DR1 dataset, we derive updated constraints on local PNG, obtaining $f_{\rm NL}=-3.3\pm9.2$.