The WHIM in XRay Current Evidence

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The WHIM in X-RayCurrent Evidence Future
Prospects
Fabrizio Nicastro (SAO, INAF-OAR) R. Williams
(Un. Of Leiden), Y. Krongold (IA-UNAM), M.L.
Conciatore (INAF-OAR), M. Elvis (CfA), J. Drake
(CfA), N. Brickhouse (CfA), S. Mathur (OSU), F.
Fiore (INAF-OAR)
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Outline

• The Missing Baryons problem and N-body simulation
  solution the Warm-Hot Intergalactic Medium
• Where should we search for it the FUV-X-ray
  Synergy
• (Ionization Correction Metallicity).
• Current Evidence XMM-RGS Confirmation of z0.011
  filament along Mkn 421
• The way Forward building the optimal FUV-X-ray
  sample for current (Chandra) and future (HST-COS
  and Constellation-X) studies

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Where are the Baryons?
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WHIM Observables
HI (FUV) and METAL (FUV X-Rays) Absorption Lines
Absorption Line Equivalent Widths Ion Column
Densities Nion Equivalent Width Ratios
Ionization Balance T, nb
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Mass and Metal Content of the WHIM
FUV X
X
FUV X
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Ionization Balance in the WHIM FUV vs X-ray
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The HI Problems

• Protons move fast in gas at T106 K
• HI Absorption Lines are Broad
• HI is only (10-7.2-10-6.2) x H in hybrid
  ionization gas with
• ?50 and T105.8-106.5 K
• BLAs are shallow

7 COS-FUV Res. El. at 1300 A
EW(BLA) 4-40 mA
Assuming AO 0.05xSolar
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WHIM Strength DetectabilityUV vs X-Rays
WOVI 60-600 (1z) mA (FUV) WHI 4-40 (1z)
mA (FUV) WOVII 0.8-8 (1z) mA
(X-Rays) Contrast FUV 1032/(0.06-0.6)
2000-20000 (0.1-1) x RFUSE/HST-STIS/COS
FUV 1215/(0.004-0.04) 30000-300000
(1-10) x RFUSE/HST-STIS/COS
X-Rays 22/(0.0008-0.008) 3000-30000
(10-100) x RChandra/XMM
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BLAs and OVII Need High-Contrast Spectra
(S/N)RE(COS) 50 2500 CPRE to detect at
5? BLAs with EW(BLA)20 mA and b 130 km
s-1 (S/N)RE(LETG) 125 15000 CPRE to
detect at 5? OVII with EW(OVII)2 mA
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FUV The WHIM is out there! Butonly of the Missing Mass
Cen Fang, 2006
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The WHIM in X-Rays 80-90 of the Missing Mass?
Fang06 (PKS2155-304) Zappacosta08
Controversial

• We stand by our Result
• (Nicastro08, Science Nicastro08a,b, ApJ)
• XMM-Newton does NOT rule out (Rasmussen07,
  ApJ) but rather confirms Chandra detections
  (Nicastro08a, ApJ)
• Chances of falsely detecting the two systems are
  0.05 and and 6 (Kaastra06, ApJ)

5000 CPRES !!!
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Statistical Significance

• N05a,b claim statistical significances of 3.5?
  and 4.8?, i.e. Pchance0.05 0.005
• K06 perform MonteCarlo and conclude that P40
  and P6 of falsely detect the two systems.
• N08n perform new MonteCarlo and confirm P0.05
  and P 3.9? respectively)
• differences due to different assumptions
• A Simple Gaussian Argument (z0.011 2 lines _at_
  3.8? 2?)
• ?(OVII)21.602 z(Mkn 421)0.03 ??
  ?(OVII)xz(Mkn 421) 648 mA
• ??(LETG)50 mA 13 Ind. Elem. Over-sampling
  by 4 52 bins
• PGauss (1-P(3.8?)) x 52 / 2 x
• x (1-P(2?)) x 59 / 2 0.02

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XMM-RGS Spectrum of Mkn 421as seen by R07
5-10 bins per resolution element

• Rasmussen07 claim no evidence, in XMM-RGS,
  of the absorption lines seen by Chandra

Continuum is too low!
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XMM-RGS spectrum of Mkn 421as seen by us
2-4 bins per resolution element
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Placing the continuum where it should be N08 vs
R07
2-4 bins per resolution element
5-10 bins per resolution element
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XMM-RGS confirmation(s) of LETG detections of WHIM
Shull96
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Future Prospects

• Short Term Chandra and XMM-Newton Ms (Metal)
  deep HST-COS (HI) (ToO Swift) observations of
  optimal targets
• uncontroversial detection of WHIM
• ?b to better than 30-50
• Long Term tens of lines of sight with previously
  detected broad HI WHIM (HST-COS), available for
  Constellation-X and/or XEUS, for hundreds (to
  thousands) of WHIM detections
• ?b to better than 1
• Ecology of the Universe
• heating-history of the Universe
• 3D Dark Matter maps

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Needs X-Ray Selection Criteria
3-10 Systems down to NOVII 4x1014 cm-2 at z
0.3
dN/dz
EWOVII 1 mA NOVII 4x1014 cm-2
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The Optimal Xray/FUV Sample

• F(0.1-2.4 keV) 0.2 mCrab
• ?F?(1200A)
• Z 0.25
• NH(Gal)
• BL-LACs QSOs

• BRASS vs VERON ( from BRASS vs
• SDSS BRASS vs 6DF Sedentary BL Survey)
• Result vs Galex, HST, FUSE

Allows the detection of 3-10 Metal Systems per
line of sight in 200-300 ks with Con-X 50-180
systems in 3.6-5.4 Ms
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The Best Target in the Universefor WHIM Studies
Up to 5 Chandra ToOs, 200 ks each, at 2 mCrab
(Swift) 55 HST-COS orbits in GTO P(1)
90 P(2)65
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Conclusions

• The WHIM has been found in OVI. But only 10 of
  the missing mass
• X-ray detections of the WHIM are few (Mkn 421,
  Nicastro et al., 2005 PKS 2155-304, Fang et al.,
  2006), but perhaps less controversial than
  thought XMM-RGS confirms LETG detection(s).
• Future WHIM studies must exploit the strong
  synergy between FUV and X-Ray spectroscopy FUV
  vital to measure HI column and metallicity, X-Ray
  needed to obtain ionization correction
• Constellation-X (or XEUS, or dedicated X-Ray WHIM
  missions) will allow the detections of 3-10 WHIM
  metal systems per line of sight between z0-0.3,
  down to NOVII 4x1014 cm-2
• These systems will imprint BLA absorption in the
  FUV, with typical
• EW4-40 mA and b130 km s-1
• To detect these systems HST-COS (S/N)RE 50 are
  needed