Galaxy and Mass Assembly (GAMA): halo formation times and halo assembly bias on the cosmic web

Understand

We present evidence for halo assembly bias as a function of geometric environment.

• By classifying GAMA galaxy groups as residing in voids, sheets, filaments or knots using a tidal tensor method, we find that low-mass haloes that reside in knots are older than haloes of the same mass that reside in voids.
• This result provides direct support to theories that link strong halo tidal interactions with halo assembly times.
• The trend with geometric environment is reversed at large halo mass, with haloes in knots being younger than haloes of the same mass in voids.