Supermassive Black Holes and their Environments Jörg M. Colberg with Tiziana Di Matteo Carnegie-Mellon University

The Simulation Simulation just introduced by Tiziana 3,547 BHs at z=1, plus all their progenitors (4.5m total) Using haloes and full particle sets at some redshifts

So what does a BH merger tree look like?

The Black Hole-Halo Connection Most massive haloes host most massive BHs At z=1, most active BHs live in haloes of mass M sun or less Open circles: satellites, with (generally) low accretion

The next step: BHs-Haloes- Environment Satellite BHs in massive haloes low-mass haloes and low-mass BHs in underdense regions Low-mass haloes/BHs in wide range of environments!

A bit of an aside: When do BHs form? Hierarchical growth along this line Most massive BHs do not follow hierarchical formation scenario

More on environments and evolution z=1 z=3 sat’s reduced accretion

Smallest BHs oblivious of environment Large number of m < 10 7 M sun BHs in – M sun haloes grow very slowly, independent of environment

BH Assembly: Mergers vs. Accretion Only for the largest BHs, environmental effect on mergers vs. accretion: BHs in denser regions have slightly higher fractions of “merged” mass

Summary The most massive BHs live in the most massive haloes etc. BUT the most massive z=1 BHs aren’t necessarily the most massive BHs at higher redshifts (c.f. Tiziana’s talk) Environmental dependencies strongest for massive (> 10 8 M sun ) BHs, both in mass, accretion rate, and mass assembly, and for satellite BHs (whose behaviour is consistent with their parent subhaloes having lost all their gas after infall into the larger halo) Most small ( 2.5 Massive (> 10 8 M sun ) BHs form anti-hierarchically, whereas smaller BHs form hierarchically