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Fabrizio Nicastro (Harvard-Smithsonian Center for Astrophysics)

Research by Fabrizio Nicastro et al. reveals findings on Missing Baryons Problem, WHIM measurements, and future prospects in galactic environments. Detailed analysis on the detection of WHIM filaments using X-ray spectra and lines of sight.

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Fabrizio Nicastro (Harvard-Smithsonian Center for Astrophysics)

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  1. Missing Baryons: the First Mass MeasurementDetection of WHIM Filaments along the Lines of Sight to MKn 421 and 1ES 1028+511 Fabrizio Nicastro (Harvard-Smithsonian Center for Astrophysics) Collaborators:S. Mathur, M. Elvis, J. Drake, F. Fiore, T. Fang. J. Bergeron, H. Marshall,Y. Krongold, D. Weinberg, A. Fruscione & The XTE-ASM Team: R. Remillard, A. Levine, H. Bradt, E. Morgan (Nicastro et al., 2004, Nature, submitted Nicastro et al., 2004, ApJ, submitted) The Environments of Galaxies: from kpc to Mpc, Crete - 2004 (F. Nicastro)

  2. Overview The Missing Baryons Problem The WHIM at z > 0: the lines of sight to Mkn 421 (Nicastro et al., 2004, ApJ, submitted) and 1ES 1028+511 (Nicastro et al., 2004, in prep.) First Measurement of Ωb(OVII) (Nicastro et al., 2004, Nature, submitted) Future Prospects The Environments of Galaxies: from kpc to Mpc, Crete - 2004 (F. Nicastro)

  3. (Rauch et al., 1998; Weinberg et al., 1997) maybe conservative by a factor 2-7, due to uncertainty in the meta-galactic radiation field (Burles & Tytler, 1998) (Bennet et al., 2003) The Baryon Budget at High z • From Observations of the Lya Forest at z=2: • Standard Bib Bang Nucleosynthesis, combined with observed light-element ratios, and CMB anisotropies measurements give: &  At High z, consistency on the estimated Baryon density The Environments of Galaxies: from kpc to Mpc, Crete - 2004 (F. Nicastro)

  4. Baryons are Missing at Low z (Fukugita, Hogan & Peebles, 1997) Galactic ‘damped’ Ly The Environments of Galaxies: from kpc to Mpc, Crete - 2004 (F. Nicastro)

  5. The Baryon Content in the Universe Mass Fraction vs Volume Fraction (Cen & Ostriker, 1999) Warm-Hot gas dominates Mass at low z Cool (Ly) gas dominates Volume at all z The Environments of Galaxies: from kpc to Mpc, Crete - 2004 (F. Nicastro)

  6. Chandra OVIII CVI NeIX OVII How to detect the WHIM Background QSO Emission (lines): A 2x2x5 Mpc3 Filament (4.5’ x 11’, at z=1): L ~ 6 x 1039 erg/s/sr at z = 1  F ~ 10-24 erg/s/cm2 Cf. Chandra limit ~10-18 in 2-4 months for point source The Environments of Galaxies: from kpc to Mpc, Crete - 2004 (F. Nicastro)

  7. WHIM is Faint • EW(OVII) ≲40 mÅ  NOVII≲1016 cm-2.Requires ≳100 ct/res.el. In Chandra-LETG or XMM-RGS • Exceptionally high quality X-ray spectra of background AGN are needed, implying either very large exposures or bright states, or both. The Environments of Galaxies: from kpc to Mpc, Crete - 2004 (F. Nicastro)

  8. Our Strategy (Chandra Cycles 4-5 and Newton-XMM Cycles 2-3) • Blazars flare to > 10 times normal • Trigger ToO (from Rossi-XTE ASM) • Outbursts last 1-2 weeks • 1st TOO on 2002 October 27: 100 ks ACIS-LETG • 2nd TOO on 2003 June 6: 100 ks HRC-LETG • Spectacular Results! The Environments of Galaxies: from kpc to Mpc, Crete - 2004 (F. Nicastro)

  9. Mkn 421: LETG Spectrum • ~ 7 Mcts in 2.3 days!! Takes 4-6 months on the brightest QSOs at z = 0.5 (F0.5-2 keV = 50 mCrab) • ~ 5300 ct/r.e., @ 21 Å Enough to detect (at > 3): EWAbs  2 mÅ, @ 21 Å Implying: NOVII  1014.8 cm-2  NH 1019 cm-2, for Z/Z = 0.1  Path Lengths  0.5 Mpc, for =50 The Environments of Galaxies: from kpc to Mpc, Crete - 2004 (F. Nicastro)

  10. Local Group WHIM <z>=0.011 WHIM <z>=0.027 WHIM WHIM and ISM Absorption The Environments of Galaxies: from kpc to Mpc, Crete - 2004 (F. Nicastro)

  11. X-ray WHIM Filaments The Environments of Galaxies: from kpc to Mpc, Crete - 2004 (F. Nicastro)

  12. WHIM Filaments in UV-FUV FUSE HST-GHRS NHI(z=0.011) < 4.7 x 1012 cm-2 NHI(z=0.027) < 8.5 x 1012 cm-2 NOVI(z=0.011) = 3.3 x 1013 cm-2 NOVI(z=0.027) < 1.4 x 1013 cm-2 The Environments of Galaxies: from kpc to Mpc, Crete - 2004 (F. Nicastro)

  13. Ionization Balance For 2 ions from the same element For 2 ions from different elements The Environments of Galaxies: from kpc to Mpc, Crete - 2004 (F. Nicastro)

  14. WHIM Solutions NVI-NVII-based OVII-based The Environments of Galaxies: from kpc to Mpc, Crete - 2004 (F. Nicastro)

  15. WHIM Solutions In Excellent Agreement with WHIM Expectations The Environments of Galaxies: from kpc to Mpc, Crete - 2004 (F. Nicastro)

  16. z=0.151 z=0.330 OVII Absorption toward 1ES 1028+511 (z=0.361) Chandra TOO on 2004, 03/11-13 Exposure = 149 ks Flux (0.5-10 keV) = 2 mCrab ~ 100 cts/res.el. (21-30 Å) NThr(OVII)>8 1015 cm-2 (3) z=0.151 The Environments of Galaxies: from kpc to Mpc, Crete - 2004 (F. Nicastro)

  17. OVII WHIM Number Density Cf. with: (Savage et al., 2002) Derived from Fang, Bryan & Canizares, 2002 The Environments of Galaxies: from kpc to Mpc, Crete - 2004 (F. Nicastro)

  18. Ωb(NOVII>7x1014 cm-2) • Mkn 421 (2 Filaments.): z=0.03 • Combined Mkn421+1ES1028+511 (3 Filaments): zeq(1ES1028+511)= 0.1; fOVII = 0.7 THE ‘MISSING’ BARYONS HAVE BEEN FOUND The Environments of Galaxies: from kpc to Mpc, Crete - 2004 (F. Nicastro)

  19. Summary • 3 X-ray WHIM Filaments detected with Chandra along two different lines of sight down to Nthres(OVII)=7x1014 and 8.8x1015 cm-2 resp. • Missing Baryons: once Lost but now Found: • Metallicity measurements constrain feedback models: [O/H]  -1.46 (z=0.011), [O/H] > -1.32 and [N/O]  0.65(z=0.027) • Chandra or XMM TOOs are the only way to go The Environments of Galaxies: from kpc to Mpc, Crete - 2004 (F. Nicastro)

  20. Chandra approved up to 2010 (possibly longer): collect data from > 5 sightlines towards blazars in outburst: up to z = 0.7 (2 to trigger in Chandra-AO5 & XMM-Newton-AO3 + 2 approved in AO6):  dNWHIM/dz, b (to better than 10 %), TWHIM(z<0.5), dTWHIM/dz, dZ/dz Long Term: mapping the WHIM up to z=1-2: needs high throughput and spectral resolution in X-ray: Constellation-X (R > 2.5 x LETG, A = 50 x LETG), XEUS (R ~ 2.5 x LETG, A = 750 x LETG) Pharos: (Elvis, Fiore et al. 2002 SPIE, astro-ph/0303444), Midex concept (CfA, Obs. Rome, JHU): R > 13 x LETG, A = 25 x LETG, Coverage: 12-150 Å. Slew on source in < 1-3 min.: about 20 Soft-GRB per year with F = 10-5 erg cm-2 (> 0.5 years on the brightest QSOs at z = 1-2). Short and Long Term Prospects The Environments of Galaxies: from kpc to Mpc, Crete - 2004 (F. Nicastro)

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