Briggs 2002

Epoch of Reionization: end of the dark ages

Evolution of the neutral IGM (Gnedin): ‘Cosmic Phase transition’

HI fraction

density Gas Temp

Ionizing intensity

6 Mpc

Cen 2002

Recombination time vs. Hubble time

CDM structure formation (PS)

Efstathiou 1995

Note: M_BH = 0.006 M_spheroid

N(1e11, z=6 – 8) = 3/arcmin^2

Gunn-Peterson effect

Barkana and Loeb 2001

Discovery of the EOR? (Becker et al. 2002)

Fast reionization at z = 6.3

=> opaque at _obs < 1 m

Fan et al. 2002

Lower limit to z_reio: GP Effect

F(HI) > 0.01 at z = 6.3

Briggs

Upper limit to z_reio: CMB anisotropies

Studying the IGM beyond the EOR: Ly alpha emission

Hu et al 2002

Galaxy at z=6.56 Loeb-Rybicki halos

Studying the IGM beyond the EOR: HI 21cm observations with the Square Kilometer Array and LOFAR

_21cm = 1e-8 _Lya

Temperatures: Spin, CMB, Kinetic and the 21cm signal

•Initially T_S= T_CMB

•T_S couples to T_K via Lya scattering

•T_K = 0.026 (1+z)^2 (wo. heating)

•T_CMB = 2.73 (1+z)

•T_S = T_CMB => no signal

•T_S = T_K < T_CMB => Absorption against CMB

•T_S > T_CMB => Emission

T_K

T_CMBT_s

Tozzi 2002

Global signature in wide field low frequency spectra (Shaver 1999)

Imaging the neutral IGM at z=8.5 (Tozzi 2002)

Galaxies: 6uJy at 2’ res

(= 20 mK)

tCDM and OCDM

QSOs: 3uJy/beam at 2’ res

With and without soft Xray heating.

30 Mpc comoving

3sigma antenna fluctuations

(Iliev et al. 2002)

Clustering of minihalos: T_vir < 1e4 K, M < 1e7 M_sun, > 100

=> no H line cooling => no star formation? (cf. Cen 2002)

Iliev et al. 2002: 3sigma fluctuations

due to statistical clustering

Difficulty with (LSS) emission observations: confusion by foreground radio sources (di Matteo 2001)

1422+23 z=3.62 Womble 1996

N(HI) = 1e13 -- 1e15 cm^-2, f(HI/HII) = 1e-5 -- 1e-6

=> Before reionization N(HI) =1e18 – 1e21 cm^-2

Cosmic Web after reionization = Ly alpha forest ( <= 10)

Cosmic Web before reionization: HI 21cm Forest

)1()10

1)((008.0 2/1

HI

S

CMB fz

T

T

•Mean optical depth (z = 10) = 1% = ‘Radio Gunn-Peterson effect’

•Narrow lines (1 to 10%, few km/s) = HI 21cm forest (= 10)

Carilli, Gnedin, Owen 2002

EOR: HI 21cm Absorption by the neutral IGM

z = 8, 10, 12

Evolution of <temperatures> in the simulation

z = 8 z = 12

Evolution of the neutral IGM

z = 10 z = 8

SKA observations of IGM absorption before the EOR

A/T = 2000 m^2/K 240 hrs 1 kHz/channel

Detection limits

Running rms: S_120 > 6 mJy in

240 hrs

KS of noise:

S_120 > 12mJy

Absorption by minihalos ( > 100) (Furlanetto & Loeb 2002)

N/z(minihalos) = N/z(IGM) = 10/unit z at z=8, > 0.02

Absorption in primordial disks toward GRBs

N/z << minihalos and IGM (<1e-4x) but

>> minihalos and IGM (>50x) => Use much fainter radio sources (100 uJy): GRB afterglow within disk?

Furlanetto & Loeb 2002 Barakana & Loeb 2000

Radio sources beyond the EOR?

Radio galaxy: 0924-220 z = 5.19 S_151 = 600 mJy

Quasar: 0913+5821 z = 5.12 S_151 = 150 mJy

Van Breugel et al 1999 Petric et al. 20021”

Luminous radio sources at very high z

M_BH = 1e9 M_sun

Inverse Compton losses off the CMB

= U_B (radio lobe)

Radio sources beyond the EOR:

sifting problem (1/1400 per 20 sq.deg.)

2240 at z > 6

1.4e5 at z > 6

USS samples (de Breuck et al.)

S_120 > 6mJy

Summary

•Study of EOR (and beyond) and first luminous structures is next big challenge in observational cosmology.

•GP effect => IGM opaque to observations at optical wavelengths => need longward of 1m or shortward of soft Xray.

•Study of neutral IGM: realm of low frequency radio astronomy.

•Emission probes large scale structure.

•Absorption probes intermediate to small scale structure (radio GP effect, HI 21cm forest, minihalos, proto-disks).

•Constrain: z_reion, detailed structure formation, nature of first luminous sources, ionizing background, IGM heating and cooling.

•LOFAR should provide first detections of the neutral IGM at z>6.

•SKA will allow for detailed studies.