1Csevilla.pdf

THE EVOLUTION OF SCALING RELATIONS IN
GALAXY CLUSTERS
Raúl Sevilla
Grupo de Astrofísica, Universidad Autónoma de Madrid, Madrid E-28049 (Spain)
raul.sevilla@uam.es
Yago Ascasíbar
Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA02138, USA
Gustavo Yepes
Grupo de Astrofísica, Universidad Autónoma de Madrid, Madrid E-28049 (Spain)
Stefan Gottlöber
Astrophysikalisches Institut Potsdam, An der Sternwarte 16, Potsdam D-14482 (Germany)
Völker Müller
Astrophysikalisches Institut Potsdam, An der Sternwarte 16, Potsdam D-14482 (Germany)
Abstract
We study the evolution of the scaling relations of clusters and groups of
galaxies from z = 1. A set of high resolution adiabatic SPH simulations has
been carried out in a ΛCDM universe and compared with the observations of
local and distant (z ∼ 0.8) clusters. The numerical sample has been extracted
from different simulated volumes (80-500 h−1 Mpc) in order to get objects
with a wide range of X-ray emmission-weighted temperatures (0.1 – 10 keV).
These objects have been resimulated with increasing resolution, ranging from
5123 to 10243 effective particles, in order to assess numerical convergence of
results. We also analysed the evolution of the radial structure of the ICM and
checked the validity of the classical approximations of hydrostatic equilibrium
and polytropic equation of state.
Keywords:
galaxies: clusters: general – cosmology: theory
JENAM ’04: Roads to Cosmology
Evolution of scaling relations
on galaxy clusters
Raúl Sevilla
Universidad Autónoma de Madrid
Collaborators
Gustavo Yepes (UAM)
Yago Ascasíbar (Harvard)
Stefan Gottlöber (AIP)
Völker Müller (AIP)
Objectives
• We intend to analyse the effect of resolution and
adiabatic processes in the thermodynamical
behaviour of ICM during the formation and
evolution of galaxy clusters.
• We use high resolution SPH numerical simulations,
disregarding non-adiabatic processes (radiative
cooling, star-formation, etc)
Self-Similar model
Isothermal and spherical ICM + hydrostatic equilibrium +
thermal bremmstrahlung leads to self-similar model (Kaiser
1986):
Fz M ∝ T3/2
Fz Mgas ∝ T3/2
where Fz = Ez (∆z/∆0)1/2,
fgas ∝ T0 ∝ M0
Ez = H(t)/H0 = (Ωm (1+z)3+1-Ωm)
Fz-1 LX ∝ T2
∆z is the overdensity (Bryan &
Norman 1998)
Fz-1 LX ∝ (Fz M)4/3 ∝ (Fz Mgas)4/3
Fz4/3 S ∝ T0
Evolutionary schemes
For a Y-X relation :
log Y = α(z) log X + β(z)
α(z) = cte
α, β constants ⇒ No evolution
β(z) ∝ (1+z)B
log Y = A log X + B log (1+z) + C
(Ettori et al 04)
B=0 ⇒ No evolution
Simulations
ΛCDM model (Ωm=0.3, ΩΛ=0.7, h=0.7, σ8=0.9)
•
2 simulations using GADGET 2:
– 80 Mpc/h:
• Initial P(k) with 10243 Fourier
modes
• 1283 particles
– 500 Mpc/h:
• Initial P(k) with 20483 Fourier
modes
• 5123 particles
•
•
18
(10+8)
high
resolution
resimulations.
High
resolution
achieved with mass-refinement
technique (Klypin et al. 2001)
All simulations are normalized to
Ωbar= 0.04
Simulations (II)
•
80 Mpc/h re-simulations
(Ascasibar et al. 2003):
9 MDM ~ 5.7 · 108 Msun
9 MSPH ~ 5.7 · 107 Msun
9 ~ 2.5 mill. particles in high
resolution area (5123 effective)
•
500 Mpc/h re-simulations:
9 MDM = 2 · 109 Msun
9 MSPH = 3.2 · 108 Msun
9 ~ 2.5 mill. particles in high
resolution area (20483 effective)
•
2-5 kpc/h smoothing length
Cluster sample (I)
• 25 galaxy clusters
• 5 redshifts:
z=0;0.25;0.5;0.75;1
z=0
z=0.25
z=0.5
z=0.75
• At z=0:
–
–
–
–
M = 5.7·1013 – 4.3·1015 Msun
Mgas = 5.7·1012 – 5.7·1014 Msun
TX = 0.6 – 10.8 keV
LX = 1.8·1043 – 1046 erg/s
z=1
80 Mpc/h
Cluster sample (II)
Ascasibar et al. 2003
500 Mpc/h
Resolution (I)
•
•
To test convergence of results, we’ve resimulated one cluster
Opening a new level of mass refinement → very high resolution
simulation (10243 efficient particles)
9 MDM ~ 3.5 · 107 Msun
9 MSPH ~ 5 · 106 Msun
9 ~ 20 mill. particles in high resolution area
9 0.5 kpc/h smoothing length
9 CPU time ~ 60 days
⇒ The most resolutive simulation without cooling ever.
Resolution (II)
10243
2 Mpc/h
DARK MATTER
5123
Resolution (III)
10243
2 Mpc/h
GAS
5123
At z=0: R200 = 0.9 Mpc/h
Resolution (IV)
5123
10243
We have reached convergence of
resolution in gravitational heating
Resolution vs physics
Resimulated
clusters at
80 Mpc/h
Observations
Tx1.9
Resimulated
clusters at
500 Mpc/h
Original
. Mvir > 1015 M
. 1014 < Mvir < 1015 500 Mpc/h
.2x1013 < Mvir < 1014 simulation
Markevitch ’98
Lx–Tx relation
Ettori et al ‘04
•
Helsdon &
Ponman 00
•
Arnaud & Evrard 99
•
Better agreement with
observations than
cooling simulations
Cooling steepens
relations and
normalization decreases
with redshift
Major mergers do not
increase scatter in the
sample
Relaxed & minor mergers
Major mergers
Ettori et al. ’04, astro-ph/0407021
Lx–Tx evolution
Ettori et al. astro-ph/0407021
log LX = β(z) + α(z) log TX
– α(z) and β(z) are
compatible with non
evolutionary scenario
– Slope is higher in Ettori
et al. simulations but not
normalisation
– Shallower relation
including major merger,
< 5% off self-similarity
All clusters fit
Relaxed & minors fit
Conclusions
• Radiative cooling and feedback make a steeper
Lx–Tx relation.
• Non-adiabatic processes do not alter slopes during
evolution (at least in Lx–Tx) → Compatibility of 2
evolutionary schemes.
• Non-adiabatic simulations are compatible with
non-evolutive scaling relations.
• Major mergers do not show greater scatter, this is
not expected to happen when lower ∆z are
considered.

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