Observing galaxy cluster Observing galaxy cluster simulations with an X-ray simulations with an X-ray

telescope telescope Elena RasiaElena Rasia

Department of Physics, Department of Physics, University of MichiganUniversity of Michigan

Chandra Fellows SymposiumChandra Fellows Symposium

Harvard-Smithsonian Center for AstrophysicsHarvard-Smithsonian Center for AstrophysicsOctober 13, 2006 October 13, 2006

COSMOLOGYCOSMOLOGY

•H0=71 +/- 2 km/s/Mpc

8=0.9 +/- 0.03

•n = 0.98 +/- 0.02 =0.72 +/-0.02

B =0.024 +/-0.003

DM h2=0.115+/-0.013

(Seljak et al. 2005)

From:

WMAP(1st year)

SDSS

2dF

weak lensing

SNe Ia

Ly- forest

Age of G.C.

(Haiman et al 2005)

Plank

SNAP

clusters

•H0=73 +/- 3 km/s/Mpc

8=0.74 +/- 0.05

•n = 0.951 +0.01/-0.02 B h2=0.0223 +/-0.0008

DM h2=0.127 +0.007/-0.013

=0.09 +/- 0.03

From:

WMAP

(3rd year)

(Spergel et al. 2006)

DUNE (Dark Universe Explorer)

DES (Dark Energy Survey)

XEUS (X-ray Evolving Universe Spectroscopy mission)

Constellation-X

X-MASX-MASX-ray MapX-ray MapSimulator Simulator

(Gardini et al 2004, Rasia et al. 2006)(Gardini et al 2004, Rasia et al. 2006)

SIMULATIONS:GADGET/GADGET2 Tree + SPH (Springel et al .’01; Springel ‘05)CMD (M 0.27, 0.7, 8 =0.8/0.9, h=0.70)

Explicit entropy conservation (Springel & Hernquist ‘02)Radiative cooling + uniform evolving UV backgroundMultiphase model for star-formation + galactic winds (Springel & Hernquist ‘03)Thermal conduction (Jubelgas et al. ‘04; Dolag et al. ‘04)Chemical enrichment from Sn-Ia and II (Tornatore et al. ’04, ‘06)Reduced-viscosity SPH scheme (Dolag et al. ‘05)

First part:

Selection of los + projection into the sky, is quite general+ computation of the spectral emissivity

Second part:Depend on the characteristics of the X-ray telescope and detector (Chandra ACIS-S, Chandra ACIS-I, XMM-Newton EPIC-MOS1&2 XMM-Newton EPIC-PN)

X-RAY EVENT FILES

which can be analyzed using the X-ray tools

X-ray MapX-ray MapSimulatorSimulator

Main ResultsMain Results

Contrast between temperature definitions in simulations and observations: TEW is not a good description of the X-ray spectroscopic temperature (Gardini et al. 2004)

Temperature to use in simulations TSL ->cosmological consequence for M-T (Mazzotta et al 2004, Rasia et al. 2005)

Study of systematics bias of mass measurement (Rasia et al. 2006) and metallicity measurement (Rasia et al. in prep.)

TEMPERATURESTEMPERATURESsimulation X-ray observation

The different degree of thermal homogeneity has strong implications on the temperature profiles: for the perturbed systems the spectral and emission-weighted temperature profiles are not in good agreement (Gardini et al. 2004)

beside being biased toward densest regions the spectroscopic temperature is also biased toward the coolest regions (Mazzotta et al. 2004)

T WTdVWdV

TEMPERATURESTEMPERATURESEmission-Weighted Spectroscopic-Like

Shock front No Shock front

Mazzotta et al. 2004, see also Vikhlinin 2006

Wsl n2 /T 0.75

Wew (T)n2

COSMOLOGICAL COSMOLOGICAL IMPLICATIONSIMPLICATIONS

TSL=(0.70±0.01)TEW+(0.29±0.05)

Rasia et al .2005, Kawahara et al. in prep

Simple theoretical arguments supported by hydro N-body simulations suggest the existence for virialized gravitational systems of a tight relation between M-T: M500=M0(kT500/1keV)

MASS-TEMPERATURE RELATIONMASS-TEMPERATURE RELATION

MsimM,

M0 is higher using Tsl instead of Tew

T_EW (Borgani et al.2004) T_SL (Rasia et al. 2005)

MASS BIASMASS BIAS• Hydrostatic equilibrium

equation

• Hydro(dynamic?) equilibrium equation

(Rasia et al. 2004, see also Kay et al. 2004, Faltenbacher et al. 2005, Lau et al. 2006, Nagai et al. 2006)

Gap explained by the velocity motions of the gas the is not completely at rest even in the center of the cluster

MASS BIASMASS BIASThe mass recovered through the HE equation are underestimated by 20%, half or more of which solved by including the kinetic pressure term (Rasia et al. 2006, see also Nagai et al. 2006).

The mass measurements reconstructed via the -model show a systematic underestimate, with typical deviation of about 40% at R2500 and R500.

SUMMARYSUMMARY Clusters are good probe to extract cosmological

parameters To study systematics bias, to verify models and

hypothesis and to test (X-ray, but not only…) methods we need SIMULATIONS

We built X-MAS that allow us to make proper comparison between simulations and observations

TEW is not a good description of Tspec -> we propose another formulation TSL -> this has relevant cosmological consequence for M-T

X-ray mass estimates present systematic bias due to different reasons -> this has to be taken into account in comparing different M-T relation present in literature