Simona Gallerani
(Osservatorio Astronomico di Roma)
The proximity effect
around high-redshift quasars
In collaboration with:
T. Roy Choudhury, X. Fan, A. Ferrara, A. Maselli
8th February 2010 2nd Roman Young Researchers Meeting
HI
HIIHII
HI
HII
HII
HII
HIHI
HII
Cosmic reionization
R
O
E
What is the epoch of reionization?
~100 Myr ≤1 Gyr ~13 Gyr~50 kyrBIG
BANG
recombinationprocess
CMB
Quasars: a class of very bright Active Galactic Nuclei
Black Hole
Accretion disk
Dust torus
SunQSO LL 1310
SunBH MM 96 1010
Particularly luminous
in the rest frame near ultra-violet,
i.e. close to the Lyα emission line
The quasar spectra we observe are strongly affected by the intervening material along the lines of sight
The Lyα forest in quasar absorption spectra
Keck telescope
e
obsz
1
REDSHIFT
α=1216 Å )1( ** z
Proximity effect around high-z quasars
€
RHII =3
4π
˙ N γ tQ
xHI nH
⎛
⎝ ⎜
⎞
⎠ ⎟
1/ 3
(Wyithe & Loeb 2004; Wyithe et al. 2005)
The observed size of quasar HII regions seems to suggest zrei~6
α=1216 Å
Gunn-Peterson through
Lyα
tQ = 107 yr
Nγ = 5.2 × 1056 s-1
Mhalo = 2.9 × 1012 h-1 M
z = 6.1
<xHI> = 0.1
Lbox = 100 h-1 Mpc
SPHSpringel &Hernquist (2003)
CRASH
Maselli et al. (2003)
Numerical simulations
Resolution: #particles=23243; mDM= 2109 M ; mgas= 2108 M
Radiative transfer simulations
Results obtained by A. Maselli
trough CRASH: a radiative transfer code
(Maselli et al. 2003)
Synthetic spectrum
Ly emission line
Boundary of the Strömgren
sphere
dR
fR
Red side of the GPthrough
Maselli, SG
, Ferrara,C
houdhury (2007)
Apparent shrinking
Rf systematically
underestimates Rd
MpcRd 3.6 MpcR f 2.4
MpcR 1.2
Q
HIIHHI tN
Rnx
3
3
4
Maselli, SG, Ferrara,Choudhury (2007), Maselli, Ferrara, SG (2009)
The analysis of ~ 20 quasars at z~6 shows that observations are consistent with a highly ionized intergalactic medium at z~6.
Proximity effect along the line of sight
Lyα
Gunn-Peterson through
α=1216 Å
Transverse proximity effect
Proximity effectalong the line of sight
Transverse proximity effect
Gunn-Peterson through
Transverse proximity effect: observationsM
ahab
al e
t al.
(200
5)
Fan et al. (2006)
QSO1
RD J1148+5252
7.0R
7.5emz
3.24BM
Mpc
QSO2
Transverse proximity effect: observations vs simulations
SG, Ferrara, Fan, Choudhury (2008)
underdense regionsunderdense regions
HII regionsHII regions
First-ever detection!
Conclusions
Quasar absorption spectra provide a huge amount of information concerning the ionization level of the intergalactic medium,
therefore being exquisite tools for constraining cosmic reionization.
The analysis of ~ 20 quasars at z~6 shows that observations are consistent with a highly ionized intergalactic medium at z~6, suggesting an epoch of reionization at earlier epochs (i.e. zrei >6).
The analysis of the spectrum of the most distant quasar known (i.e. at z =6.4) has provided the first-ever detection
of the transverse proximity effect in the hydrogen Lyα forest.
-0.53
-1.67
-2.81
-3.95
-5.09
-6.22
-7.36
dR
Neutral hydrogen map
Maselli, SG, Ferrara,Choudhury (2007)