The manifestation of secondary halo bias on the galaxy population from
  IllustrisTNG300
  We use the improved IllustrisTNG300 magneto-hydrodynamical cosmological
simulation to revisit the effect that secondary halo bias has on the clustering
of the central galaxy population. With a side length of 205 $h^{-1}$Mpc and
significant improvements on the sub-grid model with respect to the previous
Illustris boxes, IllustrisTNG300 allows us to explore the dependencies of
galaxy clustering over a large cosmological volume and wide halo-mass range. We
show, at high statistical significance, that the halo assembly bias signal
(i.e., the secondary dependence of halo bias on halo formation redshift)
manifests itself on the clustering of the central galaxy population when this
is split by stellar mass, colour, specific star formation rate, and surface
density. A significant detection is also obtained for galaxy size: at fixed
halo mass, larger central galaxies are more tightly clustered than smaller
central galaxies in haloes of mass M$_{\rm vir} \lesssim 10^{12.5}$
$h^{-1}$M$_{\odot}$. This effect, however, seems to be uncorrelated with halo
formation time, unlike the rest of the secondary dependencies analysed. We also
explore the transmission of the halo spin bias signal, i.e., the secondary
dependence of halo bias on halo spin. Although galaxy spin retains little
information about the total spin of the halo, the correlation is enough to
produce a significant galaxy spin bias signal. We discuss possible ways to
probe the spin bias effects with observations.
