1. The Chandra view of the cluster outskirts
University of Alabama in Huntsville
The Chandra view of the cluster outskirts
Andrea Morandi
With
Ming Sun, William Forman, Christine Jones
Honolulu, 08/05/2015
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2. The Virialization region of clusters
Credits: Roncarelli et al. 2007
Gas clumping
𝐶= <ne2> <ne>2
𝑃nt
Multi-T
T Ion v.s. e -
Clusters show the major axis preferentially elongated along the cosmic filaments
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3. Outskirts of clusters via stacking
320 Chandra Clusters (kT>3 keV, 0.056<z< 1.24), 20 Ms observations
Study Xray EM∝∫ 𝐧 𝐞 𝟐 𝐝𝐥 to measure ne, β, fgas out to R100
Detection of the filaments via ICM eccentricities
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4. EM profiles
kT-1/2E(z)-3EM(R/R200)
Ez=Hz/H0
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5. Stacking: method
R500 from Yx,500-M500 and then R200 from c-M from simulations
Gas density from the stacked EM∝∫ 𝒏 𝒆 𝟐 𝒅𝒍 , no spectral analysis
Modelling CXB, local+particle backgr, readout
Validation of stacking via mock simulations
Systematics: spherical modeling, HE, homogenous ICM, single-temperature spectral fit
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6. ne profile
Eckert et al
Roncarelli et al. 2006
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7. β profiles
β=- 𝟏 𝟑 dln(ne) dln(r)
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8. fgas(<R)= Mgas Mtot
fgas profiles
WMAP 9
Planck
fgas(<R)= Mgas Mtot
Biases:
Stellar fraction –
Baryon Deplet. –
Multi-T –
Clumpiness +
Pnt +
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9. fgas : `missing` baryons or `too many` baryons?
Conclusions:
Steep ne with β≥1 at R100
Detection of the filaments
fgas : `missing` baryons or `too many` baryons?
differences in ne between X-ray missions
Biases in HE, Clumping, multi-T
Cosmology WMAP (Ωb/ Ωm~0.167) v.s. Planck (Ωb/ Ωm~0.155)
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