Trends in Intracluster Metallicity

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1 Trends in Intracluster Metallicity

2 The Right Answer ICM metallicity is ~0.3 solar with a negative gradient within ~0.15 R180, as measured from Fe K lines M Fe M gas Leccardi & Molendi (2008) (For AG89 ZFe)

3 Surface Brightness Bias Be aware that ICM abundance measurements are brightness weighted Leccardi & Molendi (2008)

4 Surface Brightness Bias Most photons come from < 20% of the gas Core metallicity is overweighted in single-aperture metallicity measurements Leccardi & Molendi (2008)

5 Surface Brightness Bias Most photons come from < 20% of the gas Metals in 30-50% of ICM remain unobserved Metallicity is measured in only ~50% of the ICM Leccardi & Molendi (2008)

6 Overall ICM Metallicity

7 ICM Metallicity Made Simple f M M b 0.13 f esc M Fe,esc M Fe Z ICM Z = f escm Fe (1 f )M b f M b (1 f esc )M Fe

8 ICM Metallicity Made Simple f M M b 0.13 f esc M Fe,esc M Fe Z ICM Z = f escm Fe (1 f )M b f M b (1 f esc )M Fe

9 ICM Metallicity Made Simple f M M b 0.13 f esc M Fe,esc M Fe Z ICM Z = f escm Fe (1 f )M b f M b (1 f esc )M Fe f esc = [ Z Z ICM ] 1 f f 3

10 Iron Production by Stars M Fe,SnII M,IMF M Fe,SnIa M,IMF f Fe M Fe M,IMF Salpeter IMF yields from Portinari et al. (2004)

11 Iron Escape from Salpeter IMF M,IMF M,now 1.6 M Fe M,now M Fe, M Fe M,now M,now =0.46 f esc,fe =1 M Fe, M Fe 0.54

12 Iron Escape from Salpeter IMF M,IMF M,now 1.6 M Fe M,now M Fe, M Fe M,now M,now =0.46 f esc,fe =1 M Fe, M Fe 0.54 Similar to escape fraction implied by ICM enrichment

13 Prompt vs. Gradual Escape f esc = f prompt + f evol Escapes before being locked into long-lived stars Can escape after being released by stellar winds, PN, etc.

14 Prompt vs. Gradual Escape f esc = f prompt + f evol f evol f esc f esc Metals now in stars * 0.6/1.6 divided by all metals that that have escaped

15 Prompt vs. Gradual Escape f esc = f prompt + f evol f evol f esc f esc Significant fraction of metals originally locked into stars can escape via normal stellar mass loss (see e.g. Loewenstein 2006)

16 Metal Ejection

17 Galactic Winds What can ICM metallicity tell us about winds from galaxies at early times?

18 Stripped Gas How much of the ICM metallicity comes from ram pressure stripping of galactic gas? ESO in Abell 3627 Sun et al. (2008) Blue = X ray gas Red = H

19 Metal Ejection Mechanisms Galactic Winds rapid, occurring on starburst timescale environment independent Ram Pressure Stripping slow, occurring on infall timescale environment dependent more effective in massive systems

20 Galaxy Metallicity

21 Galaxy Metallicities: Cluster vs. Field Cluster galaxies and field galaxies share virtually the same massmetallicity relation Ellison et al. (2009) Suggestive that ejection of a galaxyʼs metals is not environment dependent

22 Galaxy Metallicities: Cluster vs. Field Galaxies with neighbors tend to have slightly greater gas-phase abundances, regardless of large-scale environment Ellison et al. (2009)

23 /Fe

24 Metallicity & Halo Mass

25 Abundance and Halo Mass Lower mass halos appear to have greater ICM metallicity, at least below ~ 5 kev Is star-formation efficiency greater in lower mass halos? Data from Snowden et al. (2008)

26 Abundance and Halo Mass Lower mass halos appear to have greater ICM metallicity, at least below ~ 5 kev Metallicity at ~0.1 R500 Is star-formation efficiency greater in lower mass halos? Data from Snowden et al. (2008)

27 Dependence of f gas on T Gas fraction in groups is depressed in groups within r 2500 but similar to clusters outside of that radius (Sun et al. 2009)

28 Group Metallicity Gradients Group metallicities are ~0.3 solar where most of the gas mass is Data from Sun et al. (2009)

29 Redshift Evolution

30 Abundance Evolution: I Modest apparent increase in ICM metallicity Significant increase since z ~ 0.5 Balestra et al. (2007)

31 Abundance Evolution: I Result does not appear to depend on prominence of the core Balestra et al. (2007)

32 Abundance Evolution: II Modest apparent increase in ICM metallicity No evolution after z ~ 0.5 Some surfacebrightness bias Maughan et al. (2008)

33 Abundance Evolution Model Assuming that cluster SNe track the globally averaged supernova rate leads to moderate evolution similar to the observed evolution Ettori (2005)

34 Metallicity Gradients

35 Entropy, Metallicity, & Buoyancy 10 3 Cavagnolo et al. (2009) 233 clusters 14.5 Buoyancy in the ICM tends to sort gas according to specific 11.0 entropy K [kev cm 2 ] K = kt n 2/3 e R [kpc] Buoyancy acts to preserve entropymetallicity correlations against mixing

36 Cool Cores & the Fe Gradient Clusters with short central cooling times (filled circles) clearly have core Fe gradients DeGrandi et al. (2004)... but flat central density profiles in clusters without cool cores may be concealing their Fe gradients

37 Production by the BCG Total amount of excess Fe in the core is consistent with in situ production by SN Ia in the BCG DeGrandi et al. (2004)

38 BCG Dominates Core Starlight Perseus Cluster Brightest cluster galaxy contains most of a clusterʼs stars at <100 kpc from the center Rebusco et al. (2005)

39 Iron Injection Profile Gradient of in situ metal ejection is much steeper than observed Fe gradient Rebusco et al. (2005)

40 Turbulent Diffusion Turbulence can produce observed gradient for D cm2 s 1 Limits on turbulent velocity imply eddy scale L 1 10 kpc Rebusco et al. (2005, 2006), David & Nulsen (2009)

41 AGN Metal Transport Chandra Metallicity in Hydra A is enhanced along the radio outflow axis to ~100 kpc scales 50 kpc Fe/H ~ Fe/H ~ 0.7 Kirkpatrick et al. (2009)

42 Fate of the Stripped Gas Stripped gas generally has lower specific entropy than the ambient medium and will sink Eventual location of stripped elements depends on mixing ESO in Abell 3627 Sun et al. (2008)

43 Ram Pressure Stripping X-ray tail of ESO is straight for ~70 kpc heat conduction into tail is highly suppressed little evidence for turbulent mixing Sun et al. (2007)

44 Simulations of Stripped Gas Simulations suggest that ram pressure stripping should be a more turbulent process than observed in ESO Roediger & Bruggen (2007) Is ICM more viscous than assumed in simulations?

45 Sinking of Stripped Gas z = 1.0 z = 0.5 z = 0.3 z = 0.2 z = 0.1 z = 0.0 Fe/H: Cora (2006)

46 Sinking of Stripped Gas Metallicity gradient produced by stripped gas continues to decline outside of core N.B.: Metal injection is assumed to be distributed like gas mass associated with galaxyʼs halo Cora (2006), see OWLS also

47 Buoyancy of SN Ia Ejecta Simple Sedov argument implies K ej 10K amb for SN Ia ejecta shocking against ICM gas Tang et al. (2009)

48 Buoyancy of SN Ia Ejecta Simple Sedov argument implies K ej 10K amb for SN Ia ejecta shocking against ICM gas Tang et al. (2009)

49 Buoyancy of SN Ia Ejecta Simple Sedov argument implies K ej 10K amb for SN Ia ejecta shocking against ICM gas Buoyancy alone could spread the central Fe gradient Tang et al. (2009)

50 Flattening at Large Radii Flat gradient at large radii suggests that most metals were originally ejected in a high-entropy state (winds, not stripping) Leccardi & Molendi (2008)

51 Feedback & Metallicity Gradients Outer metallicity profile of simulated clusters is indeed sensitive to the nature of galactic winds at early times Fabjan et al. poster

52 Answers ICM metallicity indicates fej ~ Evidence for non-salpeter IMF not compelling Apparent mass-metallicity trend due largely to gas deficit in core Observed Fe metallicity evolution consistent with production by Sn Ia AGN outflows can assist metal transport

53 Questions What is metallicity of gas at > 0.5 R500 and its gradient? Do metallicity gradients inform us about winds during formation of massive ellipticals? Do AGN outflows play a role in metal ejection? How are SNIa ejecta incorporated into ICM? How should we model mixing and viscosity in the ICM?

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