Galaxy Threshing in Dark Matter Halos roadmap: Galaxy - AIP

30 Pages·2003·1.32 MB·English

GGaallaaxxyy TThhrreesshhiinngg in Dark Matter Halos
AAlleexxaannddeerr KKnneebbee Centre for Astrophysics & Supercomputing, Swinburne University
tidal interactions − very technical
galaxy disruption − not really imaginative
rrooaaddmmaapp::
galaxy harassment − call for a lawyer
galaxy threshing − quite nifty
(cid:190) the n-body simulations
(ploughing the field)
(cid:190) the host halos
(sowing the seeds)
(cid:190) the satellite galaxies
(harvesting results)
Brad Gibson, Stuart Gill (Swinburne); Geraint Lewis (Sydney); Rodrigo Ibata (Strasbourg); Mike Dopita (ANU)
Galaxy Threshing in Dark Matter Halos, GCD-Vmeeting, 2003
the simulations:
the idea
A. generate a sample of dark matter host halos
• low resolution pre-runs:
• four 64 h-1Mpc ΛCDM simulations using 1283 particles
• high resolution re-runs:
• select eight halos and re-simulate with higher resolution
(cid:190) suite of 8 dark matter halos with:
m = 1.6 x 108 h-1M (equiv. 5123 particles)
p (cid:126)
M ≈ 3.0 x 1014 h-1M (millions of particles)
vir (cid:126)
r ≈ 5 h-1kpc (~0.5% of r )
frc vir
dt ≈ 0.2 Gyrs (disk space limitation…)
Galaxy Threshing in Dark Matter Halos, GCD-Vmeeting, 2003
the simulations:
the idea
B. get a handle on satellite galaxies in those hosts
• satellite finding:
• get formation redshift z of host: M(z ) = M(z=0) / 2
form f
• identify all objects within and around host halo
• satellite tracing:
• trace all satellites from z until z=0 (individually !)
f
hundreds of satellites in different host environments
satellite finder based upon n-body code…
Galaxy Threshing in Dark Matter Halos, GCD-Vmeeting, 2003
the simulations:
the n-body code
n-bodies grid hierarchy
MMuullttii LLeevveell AAddaappttiivvee PPaarrttiiccllee MMeesshh
• only open source AMR code
• written in C
• extreAmMeRl y= mAdeamptoivrey-M eeffsihc-iReenftinement
≡ Adaptive-Particle-Mesh
• extremely fast
• MPI parallelisation (planned…)
• hydrodynamics (planned…)
)
1 • on-the-fly analysis (under way !):
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Galaxy Threshing in Dark Matter Halos, GCD-Vmeeting, 2003
the simulations:
the satellite finder
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Galaxy Threshing in Dark Matter Halos, GCD-Vmeeting, 2003
the simulations:
the satellite tracer
(cid:190) apply satellite finder at formation time of host
(cid:190) use satellite tracer to follow each object until z 0
=
• tracer based on particles within rsat(zhalo )
vir form
(cid:190) when does a satellite dissolve ?
(cid:57) disintegration criterion based on tidal radius:
1/3
m(<r )
( )
tidal
r = D
tidal 3 M 12
less than 15 particles within r => disrupted
tidal
(cid:57) when disrupted, mass-less tracer particle still follows orbit
Galaxy Threshing in Dark Matter Halos, GCD-Vmeeting, 2003
the simulations:
satellite finder vs. satellite tracer
snapshot finder satellite tracer
satellite tracer follows objects right into the core
Galaxy Threshing in Dark Matter Halos, GCD-Vmeeting, 2003
the simulations:
some traced orbits…
all figures produced with 3D visualisation tool
that will soon be part of the MLAPM distribution
Galaxy Threshing in Dark Matter Halos, GCD-Vmeeting, 2003
the host halos
the host halos
setting the stage for the satellites
Galaxy Threshing in Dark Matter Halos, GCD-Vmeeting, 2003
the host halos:
formation times
M (z) / M (z=0)
halo age [Gyr’s] vir vir
#1 8.30
#2 6.01
#3 7.07
#4 3.42
#5 7.55
#6 4.52
#7 7.16
#8 6.01
quite a spread in age
Galaxy Threshing in Dark Matter Halos, GCD-Vmeeting, 2003