Simona Gallerani
Constraining cosmic reionization models with QSOs, GRBs and LAEs observational data
In collaboration with:
A. Ferrara, X. Fan, T. Choudhury, R. Salvaterra, P. Dayal
Astronomical Observatory of Rome
HI
HIIHII
HI
Pre-overlap stage
HII
Overlap stage Post-overlap stage
HII
HII
HIHI
HII
Reionization: a phase transition in the early Universe
Dark agesR
O
E
What is the epoch of reionization (EOR)?
?6 z
~500 kyr ~100 Myr ≤1 Gyr
z~1000 z~6z~20
Reionization process: observational constraints
Quasars
CMB11reiz
Gamma Ray Bursts
Ly Emitters
Page et al. (2007)
Komatsu et al. (2009)
Becker et al. (2003)
QSOs constraints on cosmic reionization
SDSS
~20 QSOs
@ 5.7<z<6.4
6~reiz
Fan et al. (2005)
GRBs constraints on cosmic reionization
MODELLING
DLA system
Neutral IGM{
Transmission feature around the Ly line
GRB 050904 @ z = 6.3
SUBARU TELESCOPE
2.0
0.0
HI
bestfitHI
x
x3.6reiz
(Totani et al. 2005)
(Tagliaferri et al. 2005)
(Kashikawa et al. 2006)
SUBARU DEEP FIELD
LAEs @ z=6.6
LAEs constraints on cosmic reionization
LAEs @ z=5.7
VS
No evolution LFUV
for 5.7<z<6.6
No evolution LFLyα
for 3<z<6 6.6reiz
Modeling reionization
Choudhury & Ferrara (2005/2006); Choudhury, Ferrara & SG (2008)
Free parameters: SFPopIII
SFPopII ,
escPopIII
escPopII ff ,
Log-Normal model QSOs, PopII, PopIII
Reionization models
Photo-Ionization Rate
ERMLRM
Data from McDonald & Miralda-Escude’(2001); Bolton et al. (2007); Fan et al.(2006)
Early Reionization (ERM)
7reionzHII
Highly ionized IGM at z=6
Late Reionization (LRM)
6reionz
Two-phase IGM at z>6
Simulating the Ly forest
Coles & Jones (1991)
Log-Normal model
Reionization model Choudhury & Ferrara (2006)
Optical depth
Density field(ΛCDM)
Neutral hydrogen(TIGM; UVB)
(Voigt profile)
SG, Choudhury & Ferrara (2006)
Simulated spectra
ERMLRM
Optical depth evolution
Fan et al. (2006)
Songaila (2004)
GAPSGAPS
3.67.5 z
SG, C
houd
hury
& F
erra
ra (
2006
)
Largest gap width distributionObservations vs Simulations
5106 HIx5104 HIx
6.5z3.5z
xHI<0.36 @ z=6.3
Low Redshift (zem<6) High Redshift (zem>6)
SG, F
errara, Fan, C
houdhury (2007)
ERMLRM
ERMLRM
GRBs absorption spectra
Kawai et al. (2006)
52 Å
GRB050904 @ z=6.3
Tagliaferri et al. (2005)
142 Å
GRBs absorption spectra
Kawai et al. (2006)GRB050904 @ z=6.3
Tagliaferri et al. (2005)
190 Å
GRBs absorption spectra
Kawai et al. (2006)GRB050904 @ z=6.3
Tagliaferri et al. (2005)
Largest gap probability isocontours: GRBs SG
, Sal
vate
rra,
Fer
rara
, Cho
udhu
ry (
2007
)
The ERM is twice more probable wrt the LRM
The gap sizes are consistent with xHI=6.410-
3.
5%
5%
10%
10%
40%40%
0
Lα[1
042er
g/se
c]
14
12
10
8
4
6
2
obs
91209040 9180
intL
obsL
xHI=1e-3xHI=0.05xHI=0.1
fesc =
0.1; SF
R=
113 Msun /yr; t* =
1.e8 yr
Dayal, Ferrara, SG (2008)
z f*/εDC fesc,α
4.5 3.5 0.075
5.7 3.5 0.3
6.6 3.5 0.3
z Mh (Msun) SFR(Msun/yr)
4.5 1011.1-12.5 6-160
5.7 1010.8-12.3 3-103
6.6 1010.7-12.0 2-43
Log Lα[erg/sec]
Log
N (
>L
α )
[Mpc
-3]
42.5 43 43.5
-5.5
-4.5
-3.5
-2.5
42
LAEs constraints on cosmic reionization
Kashikawa et al 06
Shimazaku et al 06
Dawson et al 07
An Early Reionization Model (ERM)
• The analysis of dark regions (gaps) in QSO absorption spectra favors a highly ionized IGM @ z~6.
• The gap size along the LOS towards the GRB050904 @ z=6.3 is consistent with xHI ~10-3.
• The evolution of the Lyα luminosity function @ 5.7<z<6.6 is well fitted by a reionization model with zrei ≥ 7.
The overall result points towards an extended reionization process
which starts at z>=11 and completes at z>=7, in agreement with WMAP5 data.
Largest gap width distributionObservations vs Simulations
Low Redshift (zem<6)
ERM LRM
SG, F
erra
ra, F
an, C
houd
hury
(20
07)
High Redshift (zem>6)
LRM
ERM
6.5z3.5z
5108 HIx6.5z
HR
Fan et al. (2006
This work
0
Lα[1
042er
g/se
c]
14
12
10
8
4
6
2
Lyα emitting galaxies
obs
91209040 9180
hffQL esc )1(3
2int
hm
b
HDC
Mt
fSFR
1*
intL
obsL
fesc fraction of ionizing photons that escape the galaxy
fα fraction of Lyα photons that escape the galaxy
Q ionizing photons rate
f* fraction of baryonic matter which forms stars over a timescale t*=εDCtH
eLLobs int
xHI=1e-3xHI=0.05xHI=0.1
fesc =
0.1; SF
R=
113 Msun /yr; t* =
1.e8 yr