Detecting the first light

Han Jiaxin

USTC,2007

http://2dark.org

Reionization

last scattering and CMB (300kyr,z~1100)

Dark age reionisation(1Gyr,z~6) f

rom first stars structure formation and

expansion till present

Expanding and cooling…

Reionization Phases

UV reionization StrÖmgren sphere Percolation / overlap Etching away

Open questions: Single epoch vs. Multiepoch (galaxy feedback,SF efficiency

…) Inside-out vs. Outside-in Reionization sources:X-ray,decaying particle…

Methods of Observation

Lyα absorption Cosmic StrÖmgren Spheres Metal lines GRB CMB polarization and anisotropy 21cm line

Lyα absorption

Lyα resonance absorption(1215.67A) UV

Continuous absorption at different z: Gun-Peterson trough

(Gun-Peterson 1965)

Z<5: Lyman alpha forest (fluctuating GP effect)

Zem= 3.62 QSO1422C23 (V = 16.5) (Keck)

Z>5: overlap of lines, strong evolution

Z>6: complete trough, τ>>1,

Fallback: saturation

Gun-Peterson Test

z~6: Dramatic decreas

e in transmitted flux

Increase in optical depth

Lya+Lyb+Lyr : phase transition

Comparison with Simulations: overlap-postoverlap

CMB Probes

Rescattering at Reionization Sensitive to Ionized fraction Testing Observables:

Large scale Polarization Small scale anisotropy

CMB Probe:Polarization

τ-A degeneracy

Polarization: Low-l EE peak (larger horizon than recombination)

Not contaminated by ISW Future Observertions: Perce

nt level constraints on partial reionization

CMB Probe:Polarization

CMB Probe: B-mode pol

New low-l BB peak Gravitational lensing: E-->B More Stringent constraints on GW

CMB Probe: Anisotropy

Patchy Reionization Secondary effects:

Ostriker-Vishniac effect:

Baryon Inhomogeneity Electron Inhomogeneity Kinetic SZ

CMB Probe: kSZ

PGM Bulk velocitykSZ

Silk dampingtSZ domination at <4’

tSZ null(217GHz)

Te=10keV,y=10-4,Vpec=500km/s

CMB Probe:Anisotropy

Small scales (<0.1deg,l>2000) Amplitude: duration of patchy phase No detection yet

21cm

Direct measurement, 3D image No saturation

21cm:Basics

Frequency:1420.4MHz,(200~9)MHz after redshift

Brightness Temperature

21cm: Interplay with CMB

Z>200: Thompson scattering, collision TCMB=Tk=Ts, TB=0

Z:30~200 Tk~1/(1+z)2,TCMB~1/(1+z) TCMB>Tk=Ts, TB<0

Z:20~30 Local coupling by Lya, Local IGM warming by X-ray TB<0, TB=0, TB>0 regions

Z:6~20 Global IGM warming by first galaxy, BH Likely TCMB<Tk, TB>0

21cm:Observation

Z=12 Z=9 Z=7

21cm:Observation

Solid: density domination

Dotted: with reionization

Blue: SKA sensitivity

Red: LOFAR sensitivity

21cm:Observational Challenges Foregrounds Ionosphere Interference

Summary