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

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

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

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

Going to high resolution Targets Targets Brightest z > 5 QSO has i’ = 18.6 Brightest z > 5 QSO has i’ = 18.6 Most have i’ (or z’) = Most have i’ (or z’) = New Keck/HIRES CCD array New Keck/HIRES CCD array 2X more sensitive in the far red 2X more sensitive in the far red Lower read noise Lower read noise Our sample Our sample 7 QSOs 7 QSOs 5.1 < z em < < z em < at z > 6 : SDSS J (z = 6.30) & SDSS J (z = 6.42) 2 at z > 6 : SDSS J (z = 6.30) & SDSS J (z = 6.42)

HIRES vs. the competition ESI data from G. Djorgovski SDSS J (z em = 5.80) FWHM = 7 km/s FWHM  60 km/s

The disappearing forest

Significant variety among sigtlines… z = 4.8

A close up Narrow transmission spikes

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

Bright gap characteristics  v EW Gap merging

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

Line blending

Reionization: Thermal predictions Simple reionzation scenario Simple reionzation scenario Abrupt Abrupt Photo-ionization dominates heating 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 Schaye et al Lower redshift: measure b(N) cutoff Problem: No lines in the forest at very high z!

Proximity zones

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

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

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