The goal of this project is to investigate how much the prediction of
the shock front distributions (in strength and volume filling) by
cosmological, hydrodynamic Al simulations depend on the underlying
numerical methods. Therefore we will investigate 3 different
cosmological hydro codes (
TVD-code,
Gadget-2 and
ENZO). We want to understand how much they differ already in their
predictions of the low density, low temperature gas, as well as how the
different ability of resolving low/high density regions and the
structure within them influences the shock distribution. We also want
to test
internal versus different external shock detection methods (e.g. based
on Density/Temperature versus velocity jumps).
The Comparison Project focouses onto 2 different volumes:
To follow a resonably resolved cosmological box with a massive
cluster we setup a box of size 100 Mpc/h with a intentionally large
value of sigma8 :
Ho= 70 km/s
Omega Matter= 0.27
Omega Lambda= 0.73
Baryonfraction = 15.9 %
n = 1
sigma8= 1.2
only 'adiabatic' physics, no preheating added.
Theri is a set of initial conditions produced by Dongsu Ryu for
64³, 128³, 256³ and 512³ dark matter particles,
inclusive some description on the data format available at
http://canopus.cnu.ac.kr/shocks/.
Here you can find some theoretical predictions of (cumulative)
massfunctions for the standard LCDM model (produced by K.Dolag) and the
model addapte here.
First column contains log10(M) in units of Msol/h, second
column has the prediction of cumulative mass function log10(N) using
Press & Schechter in units of 1/(Mpc/h)³ and third column
the same using Sheth & Tormen.
Here is an idl program to create Gadget initial conditions from
the above dark matter particle positions, setup_ic.pro.
(K.Dolag)
The ICs for the gadget runs and the simulation data can be found on clx
at CINECA under /clx/userhpe/hpedeue7/Data/ShockComp/
Performances
Dark matter particles distribution
Maps:
Shown are maps of projections of dm particles form different
resolutions and volumes.
Blue points are for the 64³ run, red for the 128³ one.
DM
particle distribution
central
slice of 100Mpc/h
30Mpc/h
'carrot'
64³
/ 128³
64³
/ 128³
Shown are maps of projections of dm particles form the different code:
red=Gadget2,
blue=Gadget2 (grid-like IC), green=ENZO.
Mass functions:
good convergence just for M>5 x 10^13 M_sol/h clusters.
Gas distribution
Color Maps:
Shown are maps of projections/slices for different
resolutions. From left to right 64³,128³,256³ and
512³
Enzo is on top, TVD is in the center and SPH is at the bottom.
Gas density and gas temperature distributions
At the best resolution, most of the volume is converged in term
of density, but
it is not converging in
temperature.
Individual Clusters: entropy priofiles
While gas density and gas temperature are similar for all codes,
gas entropy is not. TVD
and
ENZO show a peak in entropy at 2R_vir, while GADGET shows a smooth
transition.
This is true for all clusters and all resolutions.
Shock Waves
Color Maps:
Shocks were detected using the most suitable algorithm for every
code:
the Entropy-based
approach
by C.Prfommer to GADGET
the Temperature-based
approach
by Ryu & Kang to TVD
the Velocity-based
approach
by Vazza, Brunetti & Gheller to ENZO
Shown are maps of projections/slices for different
resolutions. From left to right 64³,128³,256³ and
512³,
at the Top is TVD, GADGET is in between and ENZO is at the bottom
The color scale for Mach number is shown in the figure (in log10(Mach)).
Energy Flux distribution for
shocks:
The bulk of energy release is similar.
However the different code/methods converge...to different place. TVD/ENZO show different
trend compared to GADGET in the low density
regions of external shocks (M>50).
