The role of cool clusters
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The role of cool clusters. Jelle S Kaastra SRON. The power of high spectral resolution. Simulation 10 5 s NEW configuration 2A 0335-96, central 3 arcmin (z=0.035) Excellent spectra, lots of diagnostic Even true when put at large distance. Temperature diagnostics.

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The role of cool clusters

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The role of cool clusters

The role of cool clusters

Jelle S Kaastra


The power of high spectral resolution

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

Temperature diagnostics

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

Abundance diagnostics

Abundance diagnostics

T = 1 keV

T = 0.2 keV

T = 5 keV

Measuring ion temperatures

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

Optical depths turbulence

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

Measuring turbulence

Measuring turbulence

  • Important pressure component: turbulence

  • Dynamics (Doppler shifts) important for testing e.g. merger models

  • Needs high resolution (1 eV at 1 keV)

Cluster chemistry decomposition in sn types

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

Another case m 87 werner et al 2006

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

More chemistry rare elements

More chemistry: rare elements


  • Plots: maximum EW (as function of T) of lines for CIE plasma; solar abundances


Example na in coronal spectrum

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

How to recognize a cluster

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



  • Cool clusters: high spectral resolution helps

  • Hot clusters: we see mostly featureless Bremsstrahlung but no exp(-kT) tail so poor estimate of emission measure

New minimum integration time

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!

Redshift distribution

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

How many clusters do we see

How many clusters do we see?

Alternative case

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



  • 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

Model clusters

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

Spatial distribution

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

Luminosity function

Luminosity function

  • Use recent compilation of Mullis et al. 2004 for evolving luminosity function:

  • Press-Schechter parameterization

  • Parameters are redshift (and luminosity) dependent



  • 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

Simulations for new

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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