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)