Presentazione di PowerPoint

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Was the universe neutral beyond redshift six?
Simona Gallerani
SISSA, Trieste, Italy
In collaboration with A. Ferrara X. Fan
T. Choudhury R. Salvaterra

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QSO spectra at high redshift
Fan et al. 2005
What can we learn from these observables?
Becker et al. 2003
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Simulating the Ly? forest
optical depth at the Ly? transition
Neutral hydrogen distribution
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Reionization models
EARLY REIONIZATION (ERM)
LATE REIONIZATION (LRM)
Volume Filling Factor
Photo-Ionization Rate
ERM
ERM
LRM
LRM
Data from McDonald Miralda-Escude(2001)
Bolton etal. (2005/2007) Fan etal. (2006)

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Simulated spectra
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Largest gap width distribution
Observations vs Simulations
Low Redshift (zemlt6)
High Redshift (zemgt6)
SG, Ferrara, Fan, Choudhury (arXiv0706.1054)
ERM
LRM
LRM
ERM
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Largest gap width distribution
Observations vs Simulations
Low Redshift (zemlt6)
High Redshift (zemgt6)
SG, Ferrara, Fan, Choudhury (arXiv0706.1054)
xHIlt0.36 _at_ z6.3
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Simulated spectra
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Transmissivity windows
What is the origin of the peaks?
Cosmic underdense regions
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Largest peak width distribution
Observations vs Simulations
High Redshift (zemgt6)
Low Redshift (zemlt6)
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Transverse proximity effect OBSERVATIONS
Mahabal et al (2005)
Fan et al (2006)
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Transverse proximity effect SIMULATIONS
HII Regions (case B)
SG, Ferrara, Fan, Choudhury (arXiv0706.1054)
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Transverse proximity effect first detection
OBSERVATIONS vs SIMULATIONS
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Summary
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Summary
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Additional lighthousesGRBs
? GRBs are soon expected to be found at redshifts
higher than QSOs ones. GRB 050904 _at_ z6.29
(Kawai et al. 2006)
? Afterglow spectra follow a power-law (easier
continuum determination).
? GRBs time-variability allows to a multiple
sampling of the same LOS.
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Preliminary results
GRBs absorption spectra
5 d 3 d 1 d 0.3 d 0.2 d
0.1 d
ERM
LRM
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Preliminary results
Time evolution of the dark gaps
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Preliminary results
Largest gap probability isocontours
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30
45
60
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30
45
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Conclusions
QSOs and GRBs absorption spectra favor an epoch
of reionization zrei?7
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Unwarranted assumptions
Uniform UVB
UVB fluctations at z?3 (Maselli Ferrara 2003
Bolton Haehnelt2003)
In low density regions
Photoionization equilibrium deviations SHOCKS
WORK IN PROGRESS
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QSO2
QSO1
time
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Conclusions
PART I
Current data do not require any sudden change in
the IGM ionization state _at_ z6. Observations
favour a fully ionized Universe _at_ z6.


PART II
HII region size measurement strongly overestimate
xHI if the apparent shrinking effect is not
taken into account. RT simulations are needed to
simulate QSO HII regions.
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Transmitted flux
Fan et al. (2006) Songaila (2004)
Fan et al. (2002)
Data from Fan etal. (2002) Songaila (2004) Fan
etal.(2006)
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Modeling Reionization
Choudhury Ferrara (2005/2006)