Download - Briggs 2002
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.