High resolution spectroscopy

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High resolution spectroscopy wide field

• prospects for Clusters and WHIM

Silvano Molendi (IASF Milano/INAF)
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Setting the context

Hot topics identified in ASI 2004 Feasibility
Study for GC and IGM Workpackage

• Cluster outer regions
• Cool cores
• Hard Excess emission
• Emission from WHIM/Soft Excess

?
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Why ?
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Outer Regions

• In the hirerarchical Universe Clusters form at
  the intersection of cosmic filaments through
  accretion
• Shocks are expected to form where the
  free-falling gas collides with the ICM (e.g.
  Tozzi et al. 2000).
• These shocks convert the bulk of the kinetic
  energy of the free-falling gas into thermal
  energy, a fraction of the kinetic energy may be
  retained by the shocked gas.

Borgani et al. (2004)
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Outer Regions

• The compression associated to the shock will
  amplify the strength of the magnetic fields which
  are frozen in the high conductivity plasma.
• Ram pressure stripping of the metal rich gas from
  the in-falling galaxies by the ICM will enrich
  the ICM in heavy elements.
• Direct accretion of pristine gas, never processed
  in galaxies, will have the opposite effect of
  diluting the metal content of the ICM.

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Outer Regions
Outer regions are very important, this is where
the ICM gets its energy, possibly B field and
metals, processes occuring here will influence
the cluster as a whole
As long as we do not have a solid observational
characterization of cluster outer regions our
understanding of clusters as a whole will be
limited.
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Cores

XMM-Newton and Chandra have revolutionized our
understanding of cluster cores plasma is not
cooling below a few KeV, although cooling time is
very short. Some form of heating is offseting
the cooling. Various heating mechanisms have
been investigated, no definite answer has been
reached
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Cores
One of the major difficulties is that we know
relatively little of the dynamics of the
plasma. Indirect evidence that gas motions with
velocities ½ of cs are common in cores (e.g.
Ghizzardi et al. 2005). We do not know in what
form these flows are laminar or turbulent, how
much kinetic energy with respect to total thermal
etc..

Very important to map cores using high spectral
resolution instruments with adequate spatial
resolution.
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Soft Excess/continuum

Over the last 10 years various authors have
reported evidence of soft X-ray/EUV emission in
excess of thermal emission. Both non-thermal
oand thermal (WHIM) origin have been considered.
Taken at face value some of the latest results
(i.e. Bonamente et al. 2005) imply either warm
gas with mass comprable to that of the hot plasma
or a population of relativistic electrons filling
the whole cluster.
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WHIM
Both theory and observations provide indications
that a sizeable fraction of the baryons in the
local Universe are contained in warm-hot
filaments distributed in IGM. Since WHIM is
contaminated by heavy elements it may be detected
through lines either in emission or absorption

• It would be important to
• map distribution of WHIM
• study its physical state

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How ?
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Cluster Outer Regions

Need to go a factor 100 down in SB wrt XMM/Chandra

• Large FOV 1 degree
• Large Eff. Areas gt1000 cm2
• Low Instrumental bkg (smaller than residual CXB)
• Low CXB (High spatial resolution)
• Observing strategy

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Soft Excess-continuum

See outer regions Only difference is E band
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Map WHIM in emission lines

• OVII or OVIII
• High spectral resolution 1/300
• Large FOV ½ deg
• Eff Area gt 200 cm2
• Modest spatial res. 1.5 arcmin

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Cores Dynamics

• High Resolution Spectroscopy 1/1000
• XMM-like spat. res. 15 arcsec
• Telescope Area gt 300 cm2
• Background not an issue
• FOV 20 arcmin

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Requirements

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Requirements

Costa, Perola Puglierin 2004
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Mission concepts/1
DIOS NEW

• WHIM mapping in emission
• additional science GRB emission/absorption
  lines. Galactic Foregrounds
• Will NOT address issue of cluster outer regions
• Limited contribution to core studies,
  insufficient spatial resolution

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Mission concepts/2
WFXRT Panoramix

• Cluster outer regions
• additional science medium/deep surveys (2 Nasa
  White papers)
• Will NOT address issue of cluster cores
• Will address issue of WHIM in continuum emission
  (of all possible ways of addressing the WHIM
  issue this is the weakest)

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Convergence
M1 M2
Study of low SB sources requires experiments
which differ from those used for studies of
bright point sources. The parameters you
optimize for are different. The scientific
community interested in diffuse sources is
minoritarian or under-represented. It might be
wise to think of one mission for diffuse emission.
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Convergence

• WFXRT telescope
• 2 focal plane instruments
• micro-calorimeter
• CCDs or other high spat res

• WHIM with emission lines continuum
• GRBs emission abs lines
• Cluster outer regions
• Survey
• Cool cores

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Synergy
M1 M2
Cluster Formation Process Observe gas before it
accretes on cluster Observe gas after it has
accreted Oxygen Bias Map WHIM in lines
Map WHIM in continuum Black Hole-Galaxy /
Diffuse Emission Map diffuse emission Map
point sources GRBs
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NEW and GCs outskirts
Simulation with 5 eV detector 1500cm2 area 100
sq.arcmin 0.4-0.5 r_virZ 0.2 solkT 3.0
keVz 0.02