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The z > 5 Ly α forest at high resolution

The z > 5 Ly α forest at high resolution. George Becker (Caltech) Wal Sargent (Caltech), Michael Rauch (OCIW), Rob Simcoe (MIT) IAU 199 March 18, 2005. Overview. Motivation Tour of the data Early indications Transmission gap evolution Thermal constraints on late reionization Summary.

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The z > 5 Ly α forest at high resolution

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  1. The z > 5 Lyα forest at high resolution George Becker (Caltech) Wal Sargent (Caltech), Michael Rauch (OCIW), Rob Simcoe (MIT) IAU 199 March 18, 2005

  2. Overview • Motivation • Tour of the data • Early indications • Transmission gap evolution • Thermal constraints on late reionization • Summary

  3. Observational constraints on the z ~ 6 IGM • Complete Lyα absorption in z > 6 QSOs • Lyα-emitting galaxies • WMAP τe • Each of these is (so far) consistent with a variety of reionization scenarios. • What else can we observe before going to 21 cm?

  4. Lyα at z > 5: The state of the art. • What about • Sub-structure in transmission gaps • Clustering properties • Thermal information • H I from proximity effect • ??? Mean transmitted flux eff = -Ln(<F>) Songaila (2004)

  5. Going to high resolution • Targets • Brightest z > 5 QSO has i’ = 18.6 • Most have i’ (or z’) = 19-20 • New Keck/HIRES CCD array • 2X more sensitive in the far red • Lower read noise • Our sample • 7 QSOs • 5.1 < zem < 6.4 • 2 at z > 6 : SDSS J1030+0524 (z = 6.30) & SDSS J1148+5251 (z = 6.42)

  6. HIRES vs. the competition SDSS J0836+0054 (zem = 5.80) FWHM = 7 km/s FWHM  60 km/s ESI data from G. Djorgovski

  7. The disappearingforest

  8. z = 4.8 z = 4.8 z = 4.8 z = 4.8 z = 4.8 Significant variety among sigtlines…

  9. A close up Narrow transmission spikes

  10. “Bright gaps” “Dark Gaps” Gaps Songaila & Cowie (2002), Paschos & Norman (2002)

  11. <F> Gap merging  v EW Bright gap characteristics

  12. Dark gaps Bright gaps Paschos & Norman 2004 dn(Gaps) / dz Mean

  13. Line blending

  14. Reionization: Thermal predictions • Simple reionzation scenario • Abrupt • Photo-ionization dominates heating → IGM temperature spike followed by a rapid cool down (Hui & Haiman 2003, Miralda-Escudé & Rees 1994, Theuns et al. 2002) Hui & Haiman 2003 Lower redshift: measure b(N) cutoff Problem: No lines in the forest at very high z! Schaye et al. 2000

  15. Proximity zones

  16. b vs. N bmin ~ 15 – 20 km/s T < 24,000 K

  17. Summary • New HIRES data set covering 5 < z < 6.4 • Significant detail compared to ESI • The transmitted flux in the Lyα forest disappears as transmission (“bright”) gaps get narrower and fewer. • Line blanketing • Expect F → 0 at z ~ 6.5 based on trends seen at z > 5 • No (obvious) uniform, isothermal temperature spikes in the IGM • Rules out the most simple scenario of reionization at z~6.5

  18. Future • A detailed characterization of the z > 5 Lyα forest • Simulation work • Improved constraints on TIGM, ΧH I (and therefore on reionization scenarios) •  from proximity effect measurements? • C IV measurements up to z = 5.5 • O I forest? • ???

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