Spatial Clustering of Dark Matter Halos: Secondary Bias, Neighbor Bias,
  and the Influence of Massive Neighbors on Halo Properties
  We explore the phenomenon commonly known as halo assembly bias, whereby dark
matter halos of the same mass are found to be more or less clustered when a
second halo property is considered, for halos in the mass range $3.7 \times
10^{11} \; h^{-1} \mathrm{M_{\odot}} - 5.0 \times 10^{13} \; h^{-1}
\mathrm{M_{\odot}}$. Using the Large Suite of Dark Matter Simulations
(LasDamas) we consider nine commonly used halo properties and find that a
clustering bias exists if halos are binned by mass or by any other halo
property. This secondary bias implies that no single halo property encompasses
all the spatial clustering information of the halo population. The mean values
of some halo properties depend on their halo's distance to a more massive
neighbor. Halo samples selected by having high values of one of these
properties therefore inherit a neighbor bias such that they are much more
likely to be close to a much more massive neighbor. This neighbor bias largely
accounts for the secondary bias seen in halos binned by mass and split by
concentration or age. However, halos binned by other mass-like properties still
show a secondary bias even when the neighbor bias is removed. The secondary
bias of halos selected by their spin behaves differently than that for other
halo properties, suggesting that the origin of the spin bias is different than
of other secondary biases.
