# Presentation: 197990

## The outer cluster regions: constraints from simulations X-ray & X+SZ

**The outer cluster regions: ****constraints from simulations ****X-ray & X+SZ**

**S. Ettori** (INAF/OA Bologna)
- with A. Morandi, M. Roncarelli,
- K. Dolag, S. Borgani, S. Molendi, L. Moscardini, G. Murante, P. Tozzi et al.

## SCIENTIFIC JUSTIFICATION

**SCIENTIFIC JUSTIFICATION**
- To characterize the thermodynamic of
- the X-ray emitting plasma at the virial radius
-  Which ngas, T and Sb values do we expect at Rvir ?
-  Are simulated X-ray clusters consistent with the observed ones in the outskirts ?
- Implications
- To calibrate the masses (gas and dark matter) in local
- galaxy clusters to use them as cosmological probes
- To study the accretion of primordial gas in cluster DM halos

## ICM at Rvir: Observed clusters

**ICM at R****vir****:**** ***Observed clusters*

- Sample of nearby clusters
- observed with ROSAT/PSPC
- (Neumann 2005)

****** ≈ ****0.8,  r ****-2.4**

- r/R200

- Scaled EM

*“**Outer regions of the cluster gaseous *
*atmosphere”  *Vikhlinin et al. (99):
- β~0.8 and larger by ~0.05
- of the global fit value

## ICM at Rvir: Observed clusters

**ICM at R****vir****:**** ***Observed clusters*

- A2204
- very preliminary results with ***Suzaku ***by T.Reiprich

- Sample of 60 objects observed
- with XMM (Leccardi & Molendi 08)

## ICM at Rvir: Simulated clusters

**M****vir** : 1.9-3.4e15,    **T****vir** : 5.5-9.9 keV
- simulated using 4 different physical models: **gravitational heating **plus *artificial viscosity, cooling, star formation, feedback, thermal conduction *
**R****2500****,  R****500****,  R****200****  ********  0.2,  0.49,  0.74 R****vir**
- Rvir ... sphere that encloses a mean density of ~100 c

**ICM at R****vir****:**** ***Simulated clusters*

## ICM at Rvir: Simulated clusters

**ICM at R****vir****:**** ***Simulated clusters*

**T****gas**

**n****gas**

- Roncarelli, Ettori et al 06

## ICM at Rvir: Simulated clusters  

**ICM at R****vir****:**** ***Simulated clusters  *

**Soft S****b****: **100% & 95% selected volume

## ICM at Rvir: Simulated clusters  

**ICM at R****vir****:**** ***Simulated clusters  *

**Volume selection**: from diffuse to denser regions

## ICM at Rvir: Simulated clusters

**ICM at R****vir****:**** ***Simulated clusters*

- Tgas

- ngas

- Sb [0.5-2 keV]

- Roncarelli, Ettori et al 06

- Unresolved CXB w. CXO
- (Hickox & Markevitch 05)

## ICM at Rvir: Simulated clusters

**Simulations**: 4 massive objects [Mvir 1.9-3.4e15,  Tvir 5.4-9.9 keV]
- Rvir ... sphere that encloses a mean density of ~100 c
**R****2500****, R****500****, R****200**** ******** 0.2, 0.49, 0.74 R****vir**
*Quant.*  **0.2R****vir****      0.5R****vir****               0.7R****vir ****            1.0R****vir**
- ngas          1        0.127 (0.004)   0.051 (0.002)   **0.018** (0.002)
- Tgas          1        0.735 (0.044)   0.613 (0.055)   **0.491** (0.085)
******Independently from the physics, just gravity**

**ICM at R****vir****:**** ***Simulated clusters*

## Surface brightness at R200 

**As reference, we can quote **for a T=5 keV obj at z=0,** **
**a soft X-ray surface brightness of *****8e-17 *****erg/s/cm****2****/arcmin****2**

**Surface brightness at R****200**** **

## Surface brightness at R200 simulations vs observations

- In the [0.5-2] keV band, ***slope ***of Sb = - d ln(Sb) / d ln(r)
**0.3-1.2 R****200**** **Simulations: 3.79-4.05
-                     Observations: 3.79 ± 0.38 (Neumann 05)
**0.7-1.2 R****200** Simulations: 4.29-4.54
-                     Observations: 5.7 ± 1.3 (Neumann 05)
** ****>1.2 R****200****    **Simulations: 4.90-5.67
-                     ... 40% higher than observed values at R200
- Note:  Sb ~ r1-6β  ... β=0.8/1.0,  slope~-3.8/-5.0

**Surface brightness at R****200**** ***simulations **vs** **observations*

## Surface brightness at R200 

**High-z **(z>0.3) **objects **
**with CXO**
- (Ettori et al in prep.):
*fit of the derivative of *
*ln(Sb)/ln( r) extrapolated at R**200** -4.7 ± 1.0*

**Surface brightness at R****200**** **

## Slopes: given ngas~ra,  Tgas~rb,  DM~rc 

- Sb ~r2a+1+0.4b;   0<b/a<2/3;
- Mgas>0, a+3>0;        MDM~r3+c ~ Mhyd~rb+1

- DM~r-2.5(0.2)
- Navarro05

- Tgas: [Markevitch98,
- Vikhlinin05]

- Sb from CXO & from simulations

- fgas~r0

- K~rb-2a/3~r1.1

##  Within 0.5 R200, ~95% of X-ray counts are present, but just 60% of the total energy
 Other biases affect X-ray analysis: cosmological dimming, subclumps, background

-  **Within 0.5 R****200**, ~95% of X-ray counts are present, but just 60% of the total energy
-  Other biases affect X-ray analysis: cosmological dimming, subclumps, _[background](slide18.xml)_

**X+SZ ***(in progress... A.Morandi)*

-  **With SZ data **(e.g. CBI interferometer on large FOV), we can try to recover the gas properties at R200: no dependence on z, linear dependence on clumps density, background just from thermal noise

## Joint fit of the observed X-ray T profile and SZ visibility + hydrostatic equilibrium 
 Constraints on T, ngas, DM profile

- Joint fit of the observed X-ray T profile and SZ visibility + hydrostatic equilibrium
-  Constraints on T, ngas, DM profile

**X+SZ ***(in progress... A.Morandi)*

- (***upper panels***) mock data of A2204
- (***right***)
- best-fit of A478

## CONCLUSIONS: summary

**CONCLUSIONS: **summary

-  We know what we’d observe at R200 (Tgas, Sb): X-ray observations & simulations provide a consistent picture with ngas~r-2.6  &  Tgas~r-0.4  &  Sb~1e-16erg/s/cm2/arcmin2
-  SZ data are complementary to X-ray data: a joint X+SZ analysis is a powerful tool to investigate the cluster outskirts
** **With an texp= 1 Msec and random fluctuations of 5% on the bkg components, we can reach typical uncertainties (90% c.l.) **<10%** on **K **& **T** of MEKAL with WF/TES independently

## Bkg: dominant in GCs outskirts

** **** **

**Bkg: dominant in GCs outskirts**

- cluster

- local gal

- CXB

- instr

- _[⏎](slide15.xml)_

**Notes:**
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