Simona Gallerani

1
The proximity effect around high-redshift
quasars
Simona Gallerani (Osservatorio Astronomico di
Roma)
In collaboration with T. Roy Choudhury, X. Fan,
A. Ferrara, A. Maselli

8th February 2010
2nd
Roman Young Researchers Meeting

2
Cosmic reionization
B I G B A N G
100 Myr
1 Gyr
13 Gyr
50 kyr
What is the epoch of reionization?
3
Quasars a class of very bright Active Galactic
Nuclei

Black Hole
Accretion disk
Particularly luminous in the rest frame near
ultra-violet, i.e. close to the Lya emission line
Dust torus
The quasar spectra we observe are strongly
affected by the intervening material along the
lines of sight
4
The Lya forest in quasar absorption spectra


?a1216 Å
Keck telescope
REDSHIFT
5
Proximity effect around high-z quasars

6
Numerical simulations
SPH
CRASH
Springel Hernquist (2003)
Maselli et al. (2003)
tQ 107 yr N? 5.2 1056 s-1 Mhalo 2.9
1012 h-1 M?
z 6.1 ltxHIgt 0.1 Lbox 100 h-1 Mpc
Resolution particles2?3243 mDM 2?109 M?
mgas 2?108 M?
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Radiative transfer simulations

(Maselli et al. 2003)
Results obtained by A. Maselli trough CRASH
a radiative transfer code
8
Synthetic spectrum
Maselli, SG, Ferrara,Choudhury (2007)
9
Apparent shrinking
Rf systematically underestimates
Rd
The analysis of 20 quasars at z6 shows that
observations are consistent with a highly
ionized intergalactic medium at z6.
Maselli, SG, Ferrara,Choudhury (2007), Maselli,
Ferrara, SG (2009)
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Proximity effect along the line of sight

Gunn-Peterson through

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Transverse proximity effect
Proximity effect along the line of sight
Gunn-Peterson through



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Transverse proximity effect observations
Mahabal et al. (2005)
Fan et al. (2006)
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Transverse proximity effect observations vs
simulations
underdense regions
HII regions
First-ever detection!
SG, Ferrara, Fan, Choudhury (2008)
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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 z6 shows that
observations are consistent with a highly
ionized intergalactic medium at z6, suggesting
an epoch of reionization at earlier epochs (i.e.
zrei gt6).
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 Lya forest.
15
Neutral hydrogen map

-0.53 -1.67 -2.81 -3.95 -5.09 -6.22 -7.36
Maselli, SG, Ferrara,Choudhury (2007)