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The role of cool clusters

This study explores the role of high spectral resolution in analyzing cool clusters, particularly in the context of temperature and abundance diagnostics. By employing a new configuration and extensive simulation time, we can deliver excellent spectral data even at large distances. Key findings include advancements in measuring ion temperatures, turbulence, and chemical composition, particularly through spectral lines sensitive to the optical depth. The analysis also highlights that cooler clusters benefit significantly from high-resolution techniques, allowing for a detailed understanding of their physical properties.

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The role of cool clusters

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  1. The role of cool clusters Jelle S Kaastra SRON

  2. The power of high spectral resolution • Simulation 105 s • NEW configuration • 2A 0335-96, central 3 arcmin (z=0.035) • Excellent spectra, lots of diagnostic • Even true when put at large distance

  3. Temperature diagnostics • T hard to measure for E<kT from continuum only • Multi-T plasma: need lines to resolve T-structure De Plaa et al. 2005

  4. Abundance diagnostics T = 1 keV T = 0.2 keV T = 5 keV

  5. Measuring ion temperatures • With high resolution (~ eV) possible to measure line broadening due to finite ion temperature • Important for shocks etc. Model with Ti = 0

  6. Optical depths / turbulence • Several Fe-L lines (red in figure) sensitive to optical depth, others (blue in figure) not • For known distance, this gives turbulent velocity

  7. Measuring turbulence • Important pressure component: turbulence • Dynamics (Doppler shifts) important for testing e.g. merger models • Needs high resolution (1 eV at 1 keV)

  8. Cluster chemistry: decomposition in SN types • 2A 0335+096 (top) and Sersic 159-03 (bottom) • Light elements (O, Ne, Mg) from high mass SN (type II) • Heavy elements (Fe, Ni) from WD collapse (type Ia) • Ratio II/Ia is 2-3 • Few 109 sn Ia per cluster Werner et al. 2005 De Plaa et al. 2005

  9. Another case: M 87(Werner et al. 2006) • Total exposure time: 169 ks • Clear lines from O, N, and C seen • C/Fe: 1.17±0.14 • N/Fe: 1.63±0.18 • O/Fe: 0.66±0.04 • Ne/Fe: 1.31±0.09 • Mg/Fe: 1.33±0.09 •  AGB stars for CN! Continuum-subtracted RGS spectrum

  10. More chemistry: rare elements K-shell • Plots: maximum EW (as function of T) of lines for CIE plasma; solar abundances L-shell

  11. Example: Na in coronal spectrum • Needs to find weak lines in crowded spectral area • High spectral resolution not only required for sensitivity but also for de-blending

  12. How to recognize a cluster? • Spatially extended source (classical argument); measure S/N over full or part of spectral band • Redshifted line emission spectrum (possible with high spectral resolution); Fit emission measure

  13. Results • Cool clusters: high spectral resolution helps • Hot clusters: we see mostly featureless Bremsstrahlung but no exp(-kT) tail so poor estimate of emission measure

  14. NEW: minimum integration time • Hot clusters are seen wherever they are • For high T clusters at very high z better visible! • For cool clusters, longer exposure times really help: 106 s exposure is great!

  15. Redshift distribution • For low T, cut-off due to S/N: simply too low luminosity • For high T, strong evolution effects • Above ~2 keV, we see all clusters at any redshift • Sample dominated by 1-4 keV clusters

  16. How many clusters do we see?

  17. Alternative case • Look also to alternative: 70x70 deg but 104 s exposure time (same total exposure time as 7x7 deg @ 106 s) • Relatively less cool clusters • Sample dominated by hotter clusters: 2-8 keV

  18. Conclusions • High resolution spectroscopy with a wide FOV, as offered by ESTREMO/NEW, allows to study many aspects of cluster physics in detail • In particular low T systems well ssuited thanks to their line richness • During its lifetime, ESTREMO/NEW will see many such systems at broad range in z

  19. Model clusters • Use fixed set of temperatures • Use L-T correlation (Voit 2004) to get 2-10 keV luminosity: • L = L0 (T/T0)α • L0 = 6x1037 W • T0 = 6 keV • α = 3 HIFLUCS sample Reiprich & Böhringer

  20. Spatial distribution • Use isothermal β-model • Use loose correlation between β and rc to constrain number of free parameters • Use 4 typical cases: rc = 50, 100, 200 and 400 kpc HIFLUCS sample Reiprich & Böhringer

  21. Luminosity function • Use recent compilation of Mullis et al. 2004 for evolving luminosity function: • Press-Schechter parameterization • Parameters are redshift (and luminosity) dependent

  22. Evolution • Evolution of cluster parameters highly uncertain • Use here Vikhlinin et al. 2002 based on distant clusters observed with Chandra: • For fixed T: • L~(1+z)1.5 • Mg~(1+z)-0.5 •  rc~(1+z)-5/6 for self similar evolution

  23. Simulations for NEW • Effective area 1000 cm² • ΔE = 3 eV • FOV 60’x60’ • Spatial resolution 1’ • Smallest/largest extraction radius 2/30’ • Cosmic X-ray background only

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