Intracluster Stars As A Source of Intracluster Medium Enrichment

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Intracluster Stars As A Source of Intracluster
Medium Enrichment

• Suresh Sivanandam
• Advisor A. Zabludoff Collaborators D.
  Zaritsky, A. Gonzalez

HST Image of Abell 1689
XMM Image of Abell 3112
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Intracluster Medium

• Dominant Component of Baryons in Rich Clusters
• Mgas/Mtot 0.1-0.2
• Highly enriched out to virial radius
• ZFe 0.3 Z?
• MFe prop. Mgas
• Ionized X-ray Gas
• T 2-10 keV
• Gravitationally Heated

Cluster Abundance - De Grandi et al. (2004)
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Conventional Models

• Ram Pressure Stripping
• ISM stripped as galaxy falls into cluster
• Galactic Outflows
• AGN, starburst, SNe feedback expels enriched ISM
  into ICM
• Problems
• Too many free parameters
• Difficult to track ICM metals
• Require extreme (100)
• mass loss
• Require non-standard IMF
• Maoz and Gal-Yam (2003)

HST NGC 3709 Image - NASA and Cecil, G.
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Detection of Intracluster StarsGonzalez et al.
(2005)

• I-band drift-scan imaging of 24 z0.1 clusters
  with central BCGs
• Sensitive to low surface brightness components
• All clusters are best fit by 2-component r1/4
  profile
• BCG and ICS components
• ICS properties
• 80-90 of light
• 10-40x bigger
• More elliptical
• Closely aligned
• Distinct

Smoothed surface brightness map of Abell 1651 -
Gonzalez et al. (2000)
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• Abell 2571 2-component surface brightness fit.
  Position angle and
• ellipticity breaks are best fit by 2-component
  profile - Gonzalez et
• al. (2005)

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Our Toy ModelZaritsky et al. (2004)

• How important is ICS to ICM enrichment?
• Evolution of ICS directly impacts ICM
• To quantify ICS enrichment
• Model ICS stellar population
• Compute cumulative SNe rates
• Compare with available global X-ray gas/abundance
  measurements
• ? FeICM FeEJECT ? LICL ? (M/L)ICS / MICM
• Results suggest significant contributions from
  ICS (20 - 60 )

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Limitations of Model

• Lack of spatial X-ray information to match
  optical SB profiles of ICS
• ICS is more concentrated than cluster galaxies
• Clusters typically have strong radial abundance
  gradients (cf. Slide 2)
• Require spatially-resolved comparison

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Improved Approach

• XMM-Newton MOS spatially-resolved spectroscopy of
  7 clusters
• Improve statistics
• Obtain Z(R), TX(R), LX(R)
• Determine MFe(R) and compare with predicted ICS
  value using toy model

?
Spatially-resolved spectroscopy of Abell 3112
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Results Z(R) and TX(R)
Majority of clusters have both temperature and
abundance gradients
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Results ICS contribution
A0496
A1651
A4059
A3112
New results still suggest significant ICS
contribution
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Further Refinements

• Complete analyses of 3 more clusters
• Model diffusion of metals
• Test sensitivity of results to SNe rates and
  yields
• Pursue additional discriminators between models

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Summary

• The newly detected intracluster stars make a
  significant contribution to the ICM metals
  (ranging from 100 in the central bin to 10
  at large fractions of the virial radius)
• For the proper treatment of this problem we need
  to quantify the effects of diffusion and SNe
  rates/yields
• With additional discriminators we will be able to
  compare the relative contributions of ICS
  pollution and conventional enrichment models

References De Grandi et al. 2004, AA, 419, 7
Gonzalez et al. 2000, ApJ, 536, 561 Gonzalez et
al. 2005, ApJ, 618, 195 Zaritsky et al. 2004,
ApJL, 613, L93
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