EDGE Project' WHIM Working Group' Update

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EDGE Project. WHIM Working Group.Update
Enzo Branchini Univ. Roma TRE On behalf of
the WHIM WG Alessandra Corsi
INAF/IASF Massimiliano Galeazzi Univ. of
Miami Melania Del Santo
INAF/IASF Fabrizio Fiore
INAF/OAR Pasquale Mazzotta Univ. Tor
Vergata Silvano Molendi
INAF/IASF Lauro Moscardini Univ.
Bologna Fabrizio Nicastro
INAF/OAR Luigi Piro
INAF/IASF Mauro Roncarelli Univ.
Bologna Eugenio Ursino Univ. of
Miami Matteo Viel INAF/OAT

• Bologna
• Area del CNR.
• 29/11/2006

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Outline of the Talk

• Goals
• Using CCD maps to select WHIM candidates.
• Estimate starburst galaxies contamination.
• Assess the number of detectable WHIM filaments
  using TES.
• - Preliminary absorption and emission analyses
  (Alessandra Corsi)

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Publicly available models
Absorption Spectra

• Semi analytic model (Viel et al. 2003) _at_
  http//www.rm.iasf.cnr.it/Estremo.html
• Montecarlo model (Nicastro 2006) _at_
  http//hea-www.harvard.edu/nicastro/Estremo/
• Hydrodynamical model (Viel 2006) _at_
  http//www.rm.iasf.cnr.it/Estremo.html

And transformed in Xspec-format by Melania Del
Santo and Alessandra Corsi
NEW Surface Brightness Maps
Hydrodynamical model ( Borgani et al. 2005,
Galeazzi - Ursino 2006)
Almost Ready
Emission (ready) Absorption (in progress)
Spectra
Hydrodynamical model ( Borgani et al. 2005,
Galeazzi-Ursino 2006)
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WHIM in Emission.

• Massimiliano Galeazzi
• Eugenio Ursino
• Stefano Borgani
• Massimo Roncarelli
• Lauro Moscardini.

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Cosmological hydrodynamic simulation (Borgani et
al. 2004)
Cosmological parameters
Physical parameters

• Intrinsic Metallicity (Gadget)
• Croft Model (PAr)
• Cen (Cen) Scatter

3 Different Metallicity Models
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Project Si.Li.Cone
Simulating high-resolution spectroscopic X-ray
observations of the WHIM

• CCD Field 1 deg2 (x10)
• TES Field 42x42 (x10)
• CCD Resolution 14x14
• TES Resolution 1.4X1.4
• 0 z 2
• Spectral Bands 0.38-0.65 KeV (Soft)
• 2-4
  KeV (Hard)
• vii. TES spectral resolution (1 eV)
• viii. 3 phases Hot Diffuse Dense
• ix. 3 metallicity models

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Phase diagram (_at_z0)
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Metallicity Models
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DENSE 5ltLog(T)lt7 Log r gt3
DIFFUSE 5ltLog(T)lt7 Log r lt3
HOT Log(T)gt7
1.0 10-12
3.1 10-12
6.0 10-13
8.0 10-13
1.0 10-12
2.0 10-13
1.9 10-12
6.4 10-12
1.0 10-12
Surface Brightness in the 0.38-0.65 KeV Band
units 10-12 erg/cm2/s/deg2 Galactic
Foreground 3.0 (Mc Cammon 2002) ROSAT7x
10-12 erg/cm2/s/deg2
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Selecting WHIM candidates in (simulated) EDGE-CCD
maps
3 gas phases Galactic Bkg (Mc Cammon 2002) (no
AGNs) 10 CCD maps --gt 1 deg2, 2562 pixel (res.
14) 2 bands --gt Soft (0.38-0.65 keV), Hard
(2-4) keV 1 Msec observation. Seff 1000 cm2
Maps
1) Hardness ratio (Hard/Soft) 2) Photon counts in
the Soft band
Selection criteria
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STEP 1 Definying observable WHIM candidates

• A CCD pixel contains a potentially observable
  WHIM structure if
• 1 gt40 photons (Slim) from the diffuse phase can
  be collected in 1Msec
• in the 0.38-0.65 (Soft) KeV band.
• -2 Hot and dense phase contribute lt 40 photons
  each to the total flux.
• The CCD f.o.v. contains Nw 4000 WHIM
  candidates on average

With the same criterion we select NH1240 and
ND4300 pixels in the Hot and Dense phases
respectively.
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STEP 2 measuring hardness ratios
We measure the intrinsic hardness ratio of each
phase taking into account the Galactic foreground
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STEP 2 Selecting by hardness ratio only
-3.1 lt Log(H/S) lt -1.1
Selected pixels (Red) Ns29000 (44 FOV)
Of which 3350 are WHIM candidates (green) (5
FOV) (NwNs)/Ns (Hits) 11.6 Nw(NwNs)/Nw(Misses)
17.7
Hot 67 (0.1 FOV) Hits 0.26 Misses 95
Dense 1700 (2.6 FOV) Hits 6.0 Misses 60
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STEP 3 Selecting by flux only
STot(0.38-0.65)lt ltSTot(0.38-0.65)gt
Selected pixels (Red) 57000 (87 FOV)
WHIM 3950 (6 FOV) Hits 11.6 Misses 1.2
Hot 750 (1.1 FOV) Hits 1.3 Misses 40
Dense 2400 (3.4 FOV) Hits 4.2 Misses 44
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STEP 4 Two selection criteria
-3.1 lt Log(H/S) lt -1.1
STot(0.38-0.65)lt ltSTot(0.38-0.65)gt
Selected pixels (Red) 24000 (36 FOV)
WHIM 3300 (5 FOV) Hits 13.8 Misses 17.8
Hot 96 (0.15 FOV) Hits 0.4 Misses 92
Dense 900 (1.3 FOV) Hits 3.8 Misses79
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STEP 4 Three selection criteria
-3.1 lt Log(H/S) lt -1.1
SLimBgk lt STot(0.38-0.65) lt ltSTot(0.38-0.65)gt
WHIM 4.8 FOV Hits 44.8 Misses 21.5
Hot 0.1 FOV Hits 0.8 Misses 95
Dense 1.3 FOV Hits 12.4 Misses79
If Slim 20 photons (rather than 40)
WHIM 8.6 FOV Hits 49.1 Misses 32.1
Hot 0.1 FOV Hits 0.6 Misses 94
Dense 0.8 FOV Hits 4.7 Misses79
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Starburst Contamination 1

Ranalli, Comastri Setti 2005
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Starburst Contamination 2
Contaminating sources must have gt10 photons in
the OVII line complex. Let us consider a 1Msec
observation (S1000 cm2) Best Case Scenario If
fOVII/f0.5-20.1 that translates into
f0.5-210-16 erg/cm2/s. This identifies only
300 (mostly point-like) sources above EDGE
resolution threshold (t.b.c. with 104 WHIM,
103 AGNs) Worst Case Scenario If
fOVII/f0.5-20.5 this translates into
f0.5-2gt5x10-17 erg/cm2/s. This identifies 600
sources below EDGE resolution threshold. However,
only sources with zlt0.5 contaminates the CCD
sample in the 0.38-0.65 KeV band. This constraint
reduces the number of contaminating sources by
30. The number of contaminating sources (400)
compares with 104 WHIM, 103 AGNs.
More constraints from extended vs. point-like
sources.

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How many WHIM candidates can be selected in a 1
Msec TES observation ?

• Simulation Parameters
• Slice depth 192 h-1Mpc 6 slices considered
• 10 TES Fields of View 42x42 (30x30 pixels)
• Pixel size 1.4x.14
• 1Msec Observation

• WHIM candidates (definition for EDGE-TES)
• The diffuse gas phase must contribute gt10 counts
  on a TES pixel in the OVII line complex
  (rest-frame 560-575 eV)
• Hot and Dense phases contamination below
  threshold

• Selecting WHIM candidates (in the simulation)
• Diffuse phase contributes gt10 counts per on a
  TES pixel in a single z-slice in the
  (560-575)/(1z) eV energy band.
• Other phases contribute less than 10 pixels each.

n.b. A typical WHIM candidate receives gt 60 of
the signal from the diffuse phase
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Dense Phase
CCD Maps 0.38-0.65 KeV Central Region (42x42)
Diffuse Phase
Hot Phase
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Maps of OVII emission with TES angular resolution
TES maps
Diffuse Phase (WHIM) contribution
Observable WHIM candidates after removing
hotdense phases contaminated pixels
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Full line of sight (out to z2) spectrum
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Z-slice layer 2 (whim signal)
Z-slice layer 3 (contamination)
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• Selecting WHIM candidates 2 Less contamination
• Diffuse phase contributes gt10 counts
• Other phases contribute less than 1 pixels each.

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Some statistics

• On average roughly 50 pixels host a detectable
  WHIM
• candidate in each z-slice, totaling to 30 of the
  TES field of
• view out to z0.5. The number decreases beyond
  z0.3

Residual contamination from background
sources decreases somewhat the number of WHIM
candidates.
Decreasing the contamination threshold (gt95 of
OVII flux from WHIM) affects candidates
selection at high z (up to a factor 2 _at_ z0.5).
A more demanding requirement is constituted by
angular extension. Typically one filament is
present in each f.o.v.
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Measuring WHIM angular clustering
with WFXRT

• We consider 10 different FOV of 60 X 60
  observed for 1 Ms
• each and obtain 256x256 pixel surface brightness
  maps The pixel
• size of 23x23 is chosen to meet instrument
  requirements.
• We quantify the clustering using the angular two
  point correlation
• function that we measure through Davis and
  Peebles (82) estimator.
• Flux is estimated in the 0.28-0.65 KeV band to
  maximize the OVII and OVIII line contributions
  from WHIM out to z0.5

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• Correlation signal is dominated by Hot and Dense
  phases and
• attributed to the intrinsic autocorrelation of
  extended sources.
• Signal from the diffuse phase small but
  significantly nonzero.
• Field-to-field variation dominate over Poisson
  noise (exposure
• time could be reduced or less fields need to be
  observed).

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• Unlike for the dense and hot phases
• the correlation signal of the diffuse phase
• hardly depends on the model assume for
• the IGM metallicity of the IGM in the
  hydro-dynamical simulation

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• Hot and dense phase
• are dominated by
• extended sources that
• should be easy to
• remove. A simple
• 3s-clipping procedure
• allows to remove all
• correlation but that of
• the diffuse WHIM.

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• The possibility of detecting WHIM through its
  angular correlation
• properties relies on EXTREMO/WFXRT ability of
  resolving discrete sources. As AGNs are the main
  contributors of the soft-X-ray sky
• we construct mock surface brightness maps of
  unresolved AGNs and compute the angular
  correlation function of the signal.

0.5-2 KeV Band Detection Limit 10-16
erg/cm2/sec (Molendi 2006) At this limit 10-20
of the CXB is resolved. (Moretti et al. 2003)

(Molendi 2006)

• Take a LogN-LogS model for unresolved AGN
  assuming that they contribute 5-10 to the CXB
• Assume a N(z) distribution for unresolved AGNs
• Assume that AGNs are hosted in Dark Matter halos
• Extract a sample of mock AGNs by assigning an
  x-ray flux to DM halos extracted from N-body
  simulations.

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AGN LogN-LogS Two Models
1 Moretti et al 2003 extrapolated below CHANDRA
limit. Stot5 CXB
Log N
Euclidean
2 Euclidean extrapolation below CHANDRA limit.
Stot10 CXB
CHANDRA Det. Limit
Moretti et al 2003 Extrapolated
ESTREMO Det. Limit
Moretti et al 2003
Log S
erg/cm2/s/deg2
1E-16
3E-17
7E-18
3E-19
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Flux in the 0.38-0.65 KeV band extrapolated
assuming sources with power law spectra with G1.2

• GIF Simulation of a
• LCDM model
• Stacking 10-simulation
• cubes at different epochs
• L-Cube 479 Mpc.h
• Only DM halos with
• Mgt5x1011 solar
• considered.

LogN-LogS

• Field 1 deg2
• 0 z 2
• iii Dq 23 arcsec
• iv z-sampling 8 snaps

N(z) of resolved AGNs from Hopkins (2006)
bolometric LF.
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Unresolved AGN-correlation function is
consistent with zero and significantly below that
of Diffuse WHIM. (see Croft et al. 2000) This
result is robust as it does not depend
significantly on the models assumed for the AGNs
LogN-LogS and N(z) functions.
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