Missing Baryons: Evidence and CounterEvidence

1
Missing Baryons Evidence and Counter-Evidence
Fabrizio Nicastro (CfA-SAO, INAF-OAR) Collaborato
rs S. Mathur (OSU), R. Williams (OSU), M. Elvis
(CfA), J. Drake (CfA), F. Fiore (INAF-OAR), Y.
Krongold (IA-UNAM)
2
Missing Baryons and the WHIM (59 9) of
Baryons are Missing

• Find
  the Missing Baryons and
• 
  verify theory
• 
  Ecology of the Universe dZ/dz
• -
  Absolute (needs UV) and Relative
• 
  Metallicities.
• 
  - Galaxy Superwinds (SN) vs AGN
• 
  winds, jets
• 
  - Nucleosynthesis
• 
  Heating History of the
  Universe
• 
  dT/dz
• Cosmological parameters gt 103 systems needed
• LG-WHIM is a biased measure - Need zgt0 WHIM
  absorbers to measure Wb

(Cen Ostriker, 2006)
3
WHIM Strength DetectabilityUV vs X-Rays
WOVI lt 60-600 (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 X-Rays
22/(0.0008-0.008) 3000-30000 (10-100) x
RChandra/XMM
4
The WHIM in the UV 10-20 of the Missing Mass
Cen Fang, 2006
?b(OVI) 0.22 , i.e. 10 Missing Baryons
(with ZO 0.1 Z?)
Also BLAs (Richter et al., 2006) btherm(HI) gt
45 km/s (Cf b(HI) 10-50 km/s in
Ly?-Forest) ?b(BLA) 0.27 , i.e. 10 Missing
Baryons
5
The WHIM in X-Rays 80-90 of the Missing Mass?
Chandra TOOs F(0.5-2)2x10-4 cgs CPREs5300 NOVI
Igt7x1014 cm-2
(Nicastro et al., 2005, Nature Nicastro et al.,
2005, ApJ Williams et al., 2005, ApJ)
6
The Controversy (1)

• 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.
• N07 perform new MonteCarlo and confirm P0.05
  and P lt 0.01 for the two systems (i.e. 3.5? and
  gt 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 gt ??
  ?(OVII)xz(Mkn 421) 648 mA
• ??(LETG)50 mA gt 13 Ind. Elem. Over-sampling
  by 4 gt 52 bins
• gt PGauss (1-P(3.8?)) x 52 / 2 x
• x (1-P(2?)) x 59 / 2 0.02

7
The Controversy (2)

• Differences are due to different assumptions
• K06 compute
  
• gt PChance(z0.011) 40 !!!
• N07 compute
• gt PChance(z0.011) 0.05

8
The Controversy (2)

• Rasmussen06 claim no evidence, in XMM-RGS,
  of the absorption lines seen by Chandra

RLETG 2.4 x RRGS
XMM does not rule out Chandra Detections
9
Beyond the Controversy PKS 2155-304 (z0.116)
3.7?
4.5?
10
Fluctuation and LETG Calibration
11
The Way Forward

• Short Term
• FUV
• Systematic search of BLAs and OVI on archival
  STIS and archival and new FUSE
• KOS in 2009 deep observations of BLAs and
  moderate-to-high-z OVI
• X-Rays
• Only pursuable way with Chandra and XMM Multi-Ms
  observations of higher-z, low-NHGal,
  strategically selected (i.e. BLAs, OVI, or pilot
  X-ray spectra) bright targets i.e. 1ES 1028511
  (z0.361)
• On quiescent targets RGS slightly better than
  Chandra where both RGSs are present, because of
  high LETG background
• LETG is the only instrument at gt 40 A
  sensitivity at C 4 times better than at O
• Long Term
• UV HST-COS
• X-Rays Needs large Aeff High Spectral
  Resolution Constellation-X or small dedicated
  grating missions

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Conclusions

• WHIM detected in the UV but lt 10 of Missing
  Baryons
• In X-Rays gt 80 of Missing Baryons current
  evidence are controversial.
• WHIM detection within reach of Chandra and XMM
  only lt 0.2 of Chandra and XMM time dedicated to
  WHIM studies 20x longer exposures can provide
  firm detection of the Missing Baryons along 2-3
  l.o.s.
• Way Forward Multi-Ms LETG and RGS exposures of
  smartly selected targets (zgt0.3, NH lt 1.5x1020
  cm-2, F0.5-2 1 mCrab, OVI or BLAs, etc.).
• Future Constellation-X (or future small/mid-size
  high-res X-ray spectrometers) can detect 200
  OVII systems in 6 Ms (30 lines of sight)