Supermassive Black Holes and their Environments

Jörg M. Colbergwith 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

1012 Msun or less

Open circles: satellites, with (generally) low accretion

The next step: BHs-Haloes-Environment

Satellite BHs in massive haloes

low-mass haloesand 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 followhierarchical formation scenario

More on environments and evolution

z=1

z=3

sat’s

reducedaccretion

Smallest BHs oblivious of environment

Large number of m < 107 Msun BHs in 1011 – 1012 Msun 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 (>

108 Msun) 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 (< 107 Msun) BHs grow thru very slow accretion, with no mergers, independent of environment, with high zf > 2.5

• Massive (> 108 Msun) BHs form anti-hierarchically, whereas smaller BHs form hierarchically