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Observing galaxy cluster simulations with an X-ray telescope . Elena Rasia Department of Physics, University of Michigan Chandra Fellows Symposium Harvard-Smithsonian Center for Astrophysics October 13, 2006 . COSMOLOGY. From: WMAP (3rd year). From: WMAP(1st year) SDSS 2dF

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observing galaxy cluster simulations with an x ray telescope

Observing galaxy cluster simulations with an X-ray telescope

Elena Rasia

Department of Physics,

University of Michigan

Chandra Fellows Symposium

Harvard-Smithsonian Center for AstrophysicsOctober 13, 2006

cosmology
COSMOLOGY

From:

WMAP

(3rd year)

From:

WMAP(1st year)

SDSS

2dF

weak lensing

SNe Ia

Ly- forest

Age of G.C.

  • H0=73 +/- 3 km/s/Mpc
  • 8=0.74 +/- 0.05
  • n = 0.951 +0.01/-0.02
  • 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
  • B h2=0.0223 +/-0.0008
  • DM h2=0.127 +0.007/-0.013
  •  =0.09 +/- 0.03

(Spergel et al. 2006)

(Seljak et al. 2005)

DUNE (Dark Universe Explorer)

DES (Dark Energy Survey)

XEUS (X-ray Evolving Universe Spectroscopy mission)

Constellation-X

SNAP

Plank

clusters

(Haiman et al 2005)

x mas x ray map simulator 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 background

Multiphase 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)

X-MASX-ray MapSimulator (Gardini et al 2004, Rasia et al. 2006)

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

main results
Main 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.)

temperatures
TEMPERATURES

simulation

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)

temperatures1
TEMPERATURES

Spectroscopic-Like

Emission-Weighted

Shock front

No Shock front

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

Mazzotta et al. 2004, see also Vikhlinin 2006

cosmological implications
COSMOLOGICAL IMPLICATIONS

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)

TSL=(0.70±0.01)TEW+(0.29±0.05)

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

mass temperature relation
MASS-TEMPERATURE RELATION

M0 is higher using Tsl instead of Tew

T_EW (Borgani et al.2004)

T_SL (Rasia et al. 2005)

M,

Msim

mass bias
MASS 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 bias1
MASS BIAS

The 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.

summary
SUMMARY
  • 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
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