7/28/2019 Ak Poster Aas 6

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A Cold Channel for Black Hole Accretion and Feedback

in Cosmological SimulationsAmit Kashi, Kentaro Nagamine, Daniel Proga - University of Nevada, Las Vegas

Motivation:Accretion onto Super Massive Black Holes (SMBH) in cosmological simulations is commonly done by

assuming that the SMBH is accreting at i ts Bondi rates.

However, the Bondi prescription gives an accretion rate about 100-400 times too low to account for

the fast grow of SMBHs at high z.

We propose a new prescription with a more detailed physics to account for the accretion rate.

The main problem is the very simplifying assumptions used to obtain the Bondi accretion:

Radial accretion

Homogeneous medium (constant T and rho at infinity) Only the BH is the gravitational source

The two only forces are gravity and gas pressure

Spherical symmetry

These assumptions poorly describe accretion onto SMBHs in galaxies.

Also in cosmological scales only the hot gas participates in the accretion while in practice accretion

of cold gas is the main mode of accretion.

ow chart describing our model. The main block is the GADGET-3 SPH code which contains three engines (equation solvers) for

mology, gravity, and hydrodynamics. Four types of particles are in use: gas, stars, BHs and dark matter. The arrows indicate the

ection of information flow between the different parts of the models, where red lines (arteries) represent data going out from the

n GADGET-3 code into sub-routines, and the blue lines (veins) represent results coming back to the main GADGET-3 code (the

ck bi-directional error is equivalent to a red and a blue arrow together). Supernova feedback is also present in the code and as

cated when stars satisfy the equations for becoming a SN energy is ejected to the surrounding gas. The main block we model is the

N accretion and feedback block, which we implement with accretion according to the Bernoulli equation and three types of

dback (thermal, mechanical and x-ray feedback).

Model Flow Chart

Results

Observations

(Shankar+2004) Simulations results byDi Matteo+(2008)

Assuming 100Bondi accretion rate

The MBH M* relation

Simulations results by

Di Matteo+(2008)

Our model

Theory (Haring &

Rix 2004)

BH mass growth rate in Eddington unitsBH mass as a function of redshift

All SMBHs in simulation box Two most massive SMBHs

BH mass density

The Accretion Condition:

Mass inflow to SMBH if it is gravitationally bound to the SMBH

according to Bernoulli condition B(t)