Understanding higher-order nonlocal halo bias at large scales by
  combining the power spectrum with the bispectrum
  Understanding the relation between underlying matter distribution and biased
tracers such as galaxy or dark matter halo is essential to extract cosmological
information from ongoing or future galaxy redshift surveys. At sufficiently
large scales such as the BAO scale, a standard approach for the bias problem on
the basis of the perturbation theory (PT) is to assume the `local bias' model
in which the density field of biased tracers is deterministically expanded in
terms of matter density field at the same position. The higher-order bias
parameters are then determined by combining the power spectrum with
higher-order statistics such as the bispectrum. As is pointed out by recent
studies, however, nonlinear gravitational evolution naturally induces nonlocal
bias terms even if initially starting only with purely local bias. As a matter
of fact, previous works showed that the second-order nonlocal bias term, which
corresponds to the gravitational tidal field, is important to explain the
characteristic scale-dependence of the bispectrum. In this paper we extend the
nonlocal bias term up to third order, and investigate whether the PT-based
model including nonlocal bias terms can simultaneously explain the power
spectrum and the bispectrum of simulated halos in $N$-body simulations. We show
that the power spectrum, including density and momentum, and the bispectrum
between halo and matter in $N$-body simulations can be simultaneously well
explained by the model including up to third-order nonlocal bias terms up to
k~0.1h/Mpc. Also, the results seem in a good agreement with theoretical
predictions of a simple coevolution picture, although the agreement is not
perfect. These demonstration clearly shows a failure of the local bias model
even at such large scales, and we conclude that nonlocal bias terms should be
consistently included in order to model statistics of halos. [abridged]
