Assembly bias in the local PNG halo bias and its implication for $f_{\rm NL}$ constraints

Understand

We use $N$-body simulations to study halo assembly bias (i.e., the dependence of halo clustering on properties beyond total mass) in the density and primordial non-Gaussianity (PNG) linear bias parameters $b_1$ and $b_\phi$, respectively.

• We consider concentration, spin and sphericity as secondary halo properties, for which we find a clear detection of assembly bias for $b_1$ and $b_\phi$.
• At fixed total mass, halo spin and sphericity impact $b_1$ and $b_\phi$ in a similar manner, roughly preserving the shape of the linear $b_\phi(b_1)$ relation satisfied by the global halo population.
• Halo concentration, however, drives $b_1$ and $b_\phi$ in opposite directions.