Cosmic reionization and the history of the neutral intergalactic medium

LANL

Chris Carilli May 23, 2007

Current constraints on the IGM neutral fraction with cosmic epoch (Fan, Carilli, Keating 2006 ARAA)

Neutral Intergalactic Medium (IGM) – HI 21cm telescopes, signals, and challenges

Objects within reionization – recent observations of molecular gas, dust, and star formation, in the host galaxies of the most distant QSOs, and more…

Ionized

Neutral

Reionized

Chris Carilli (NRAO)

Berlin June 29, 2005

WMAP – structure from the big bang

Hubble Space Telescope Realm of the Galaxies

Dark Ages

Twilight Zone

Epoch of Reionization

• Last phase of cosmic evolution to be tested • Bench-mark in cosmic structure formation indicating the first luminous structures

QuickTime™ and aYUV420 codec decompressor

are needed to see this picture.

Gnedin 03

Reionization: the movie

8Mpc comoving

Barkana and Loeb 2001

Constraint I: Gunn-Peterson Effect

z

Gunn-Peterson Effect

Fan et al 2006

Gunn-Peterson limits to f(HI)

End of reionization?

f(HI) <1e-4 at z= 5.7

f(HI) >1e-3 at z= 6.3

Difficulties with GP

• to f(HI) conversion requires ‘clumping factor’

• >>1 for f(HI)>0.001 => low f() diagnostic

• GP => Reionization occurs in ‘twilight zone’, opaque for obs <0.9 m

GP = 2.6e4 f(HI) (1+z)^3/2

Reionization and the CMB

Thomson scatting during reionization (z~10)

Acoustics peaks are ‘fuzzed-out’ during reionization.

Problem: degenerate with intrinsic amplitude of the anisotropies.

Surface of last-scattering z~1000

No reionization

Reionization

CMB angular power spectrum

TT

TE

EE

Constraint II: CMB large scale polarization -- Thomson scattering during reionization

Scattered CMB quadrapole => polarized

Large scale: horizon scale at reionization ~ 10’s deg

Signal is weak:

TE = 10% TT (few uK)

EE = 1% TT

EE (l ~ 5)~ 0.3+/- 0.1 uK

Page + 06; Spergel 06

TT

TE

EE

Constraint II: CMB large scale polarization -- Thomson scattering during reionization

e = 0.09+/-0.03

Rules-out high ionization fraction at z> 15

Allows for finite (~0.2) ionization to high z

Most action occurs at z ~ 8 to 14, with f(HI) < 0.5

Page + 06; Spergel 06

es with CMB polarization:

e = integral measure to recombination=> allows many IGM histories

• Still a 3 result (now in EE vs. TE before)

Combined CMB + GP constraints on reionization

• Highest redshift quasar known (tuniv = 0.87Gyr)• Lbol = 1e14 Lo

• Black hole: ~3 x 109 Mo (Willot etal.)• Gunn Peterson trough (Fan etal.)

Pushing into reionization: QSO 1148+52 at z=6.4

1148+52 z=6.42: Gas detection

Off channelsRms=60uJy

46.6149 GHzCO 3-2

• M(H2) ~ 2e10 Mo

• zhost = 6.419 +/- 0.001

(note: zly = 6.37 +/- 0.04)

VLA

IRAM

VLA

Constrain III: Cosmic Stromgren Sphere

• Accurate zhost from CO: z=6.419+/0.001

• Proximity effect: photons leaking from 6.32<z<6.419

z=6.32

•‘time bounded’ Stromgren sphere: R = 4.7 Mpc• tqso = 1e5 R^3 f(HI)~ 1e7yrs or • f(HI) ~ 1 (tqso/1e7 yr)

White et al. 2003

Loeb & Rybicki 2000

CSS: Constraints on neutral fraction at z~6 Nine z~6 QSOs with CO or MgII redshifts: <R> = 4.4 Mpc (Wyithe et al. 05; Fan et al. 06; Kurk et al. 07)

GP => f(HI) > 0.001

If f(HI) ~ 0.001, then <tqso> ~ 1e4 yrs – implausibly short given QSO fiducial lifetimes (~1e7 years)?

Probability arguments + size evolution suggest: f(HI) > 0.05

Wyithe et al. 2005

=tqso/4e7 yrs

90% probability x(HI) > curve

P(>xHI)

Fan et al 2005

Cosmic Stromgren Surfaces (Hui & Haiman)

• Larger CSS in Ly vs. Ly = Damping wing of Ly?

• Large N(HI) => f(HI) > 0.1

zhost

Difficulties for Cosmic Stromgren Spheres and Surfaces

(Lidz + 07, Maselli + 07)

Requires sensitive spectra in difficult near-IR band

Sensitive to R: f(HI) R^-3

Clumpy IGM => ragged edges

Pre-QSO reionization due to star forming galaxies, early AGN activity

Cosmic ‘phase transition’?

Not ‘event’ but complex process, large variance time/space

Current observations suggest: zreion ~ 6 to 14

Good evidence for qualitative change in nature of IGM at z~6

Current probes are all fundamentally limited in diagnostic power

Studying the pristine neutral IGM using redshifted HI 21cm observations (100 – 200 MHz)

Large scale structure

cosmic density,

neutral fraction, f(HI)

Temp: TK, TCMB, Tspin

)1()10

1)((008.0 2/1 δ +

+= HI

S

CMB fz

TT

1e13 Mo

1e9 Mo

Multiple experiments under-way: ‘pathfinders’

MWA (MIT/CfA/ANU) LOFAR (NL)

21CMA (China) SKA

Signal I: Global (‘all sky’) reionization signature in low frequency HI spectra

Ly coupling: Tspin=TK < TCMB

IGM heating: Tspin= TK > TCMB

Gnedin & Shaver 03

140MHz

Signal ~ 20mK < 1e-4 sky

EDGES (Bowman & Rogers MIT)

All sky reionization HI experiment. Single broadband dipole experiment with (very) carefully controlled systematics + polynomial baseline subtraction (7th order)

Treion < 450mK at z = 6.5 to 10

Sky > 150 K rms = 75 mK

VaTech Dipole Ellingson

Signal II: HI 21cm Tomography of IGM Zaldarriaga + 2003

z=12 9 7.6

TB(2’) = 10’s mK

SKA rms(100hr) = 4mK

LOFAR rms (1000hr) = 80mK

Signal III: 3D Power spectrum analysis

SKA

LOFAR

McQuinn + 06

only

+ f(HI)

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

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

Signal IV: Cosmic Web after reionization

Ly alpha forest at z=3.6 ( < 10)

Womble 96

z=12 z=819mJy

130MHz

• radio G-P (=1%)

• 21 Forest (10%)

• mini-halos (10%)

• primordial disks (100%)

Signal IV: Cosmic web before reionization: HI 21Forest

• Perhaps easiest to detect (use long baselines)

• Requires radio sources: expect 0.05 to 0.5 deg^-2 at z> 6 with S151 > 6 mJy?

159MHz

GMRT 230 MHz – HI 21cm abs toward highest z (~5.2) radio AGN

0924-220 z=5.2

S230MHz = 0.5 Jy

1”

8GHz Van Breugel et al.

GMRT at 230 MHz = z21cm

RFI = 20 kiloJy !

CO Klamer +

M(H2) ~ 3e10 Mo

GMRT 230 MHz – HI 21cm abs toward highest z radio AGN (z~5.2)

rms(20km/s) = 5 mJy

229Mhz 0.5 Jy232MHz 30mJy

rms(40km/s) = 3mJy

N(HI) ~ 2e20TS cm^-2 ?

Signal V: Cosmic Stromgren spheres around z > 6 QSOs

0.5 mJy

LOFAR ‘observation’:

20xf(HI)mK, 15’,1000km/s

=> 0.5 x f(HI) mJy

Pathfinders: Set first hard limits on f(HI) at end of cosmic reionization

Easily rule-out cold IGM (T_s < T_cmb): signal = 360 mK

Wyithe et al. 2006

5Mpc

Signal VI: pre-reionization HI signal, eg. Baryon Oscillations

Very low frequency (<75MHz)= Long Wavelength Array

Very difficult to detect

Signal: 10 arcmin, 10mk => S30MHz = 0.02 mJy

SKA sens in 1000hrs:

= 20000K at 50MHz =>

rms = 0.2 mJy

Need > 10 SKAs

Need DNR > 1e6

z=50

z=150

Barkana & Loeb 2005

Challenge I: Low frequency foreground – hot, confused sky

Eberg 408 MHz Image (Haslam + 1982)

• 90% = Galactic foreground.

• Coldest regions: T ~ 100z)^-2.6 K

• 10% = Egal. radio sources = 1 source/deg^2 with S140 > 1 Jy

Solution: spectral decomposition (eg. Morales, Gnedin…)

Foreground = non-thermal = featureless over ~ 100 MHz

Signal = fine scale structure on scales ~ few MHz

10’ FoV; SKA 1000hrs

Xcorrelation/Power spectral analysis in 3D – different symmetries in freq space

Freq

Signal

Foreground

Signal/Sky ~ 2e-5

‘Isoplanatic patch’ = few deg = few km

Phase variation proportional to wavelength^2

74MHz Lane 03

Challenge II: Ionospheric phase errors – varying e- content

TID

Solution:

Wide field ‘rubber screen’ phase self-calibration = ‘peeling’

Virgo A VLA 74 MHz Lane + 02

QuickTime™ and aCinepak decompressor

are needed to see this picture.

15’

Ionospheric phase errors: The Movie

Challenge III: Interference

100 MHz z=13

200 MHz z=6

Solutions -- RFI Mitigation (Ellingson06)

Digital filtering: multi-bit sampling for high dynamic range (>50dB)

Beam nulling/Real-time ‘reference beam’

LOCATION!

Beam nulling -- ASTRON/Dwingeloo (van Ardenne)

Factor 300 reduction in power

VLA-VHF: 180 – 200 MHz Prime focus CSS search Greenhill, Blundell (SAO); Carilli, Perley (NRAO)

Leverage: existing telescopes, IF, correlator, operations

$110K D+D/construction (CfA)

First light: Feb 16, 05

Four element interferometry: May 05

First limits: Winter 06/07

Project abandoned: Digital TV

KNMD Ch 9

150W at 100km

RFI mitigation: location, location location…

100 people km^-2

1 km^-2

0.01 km^-2

(Briggs 2005)

Challenge IV: Extreme computing

LOFAR: IBM Blue Gene/L

“Stella” (Falcke)

• 0.5 Tbit/s input data rate

• 30 Tflop

• ~ 12000 PCs

• Occupying 6 m2

• 150 KW power consumption

~1.7% slower than #1 in Europe

(Barcelona) …

Dutch minister of science

Blue Gene

Focus: Reionization (power spec,CSS,abs)

PAPER: Staged Engineering Approach

• Broad band sleeve dipole => 2x2 tile

• 8 dipole test array in GB (06/07) => 64 station array in WA (07/08)

• FPGA-based ‘pocket correlator’ from Berkeley wireless lab => custom design.

BEE2: 5 FPGAs, 500 Gops/s

• S/W Imaging, calibration, PS analysis: Miriad => Python + CASA, including ionospheric ‘peeling’ calibration + MFS

• ‘Peel the problem onion’

100MHz 200MHz

PAPER: First images/spectra

Cygnus A

1e4Jy

Cas A 1e4Jy

3C392

200Jy

3C348 400Jy

140MHz

180MHz

CygA 1e4Jy

Destination: Moon!

RAE2 1973

No interference

No ionosphere (?)

Easy to deploy and maintain (high tolerance electroncs + no moving parts)

10MHz

Radio astronomy – Probing Cosmic Reionization

•‘Twilight zone’: study of first light limited to near-IR to radio

• First constraints: GP, CMBpol => reionization is complex and extended:

z_reion = 6 to 11

• HI 21cm: most direct probe of reionization

•Low freq pathfinders:

All-sky, PS, CSS

• SKA: imaging of IGM

European Aeronautic Defence and Space Corporation/ASTRON (Falcke)

• Payload = 1000 kg (Ariane V)

• 100 antennas at 1-10 MHz ~ 1/10 SKA

QuickTime™ and aYUV420 codec decompressor

are needed to see this picture.

END

•IPS/ISS angular/temporal broadening: 1MHz => 1deg, 5years

•Faraday rotation => no linear polarization

•High sky temperature

•Low power super computing: LOFAR/Blue Gene = 0.15MW

•Lunar ionosphere: p = 0.2 to 1MHz (LUNA19,20 1970’s)?

•Diffraction limits: how sharp is knife’s edge?

Very low frequencies (<10MHz): Lunar challenges

ARTICLE 22(ITU Radio Regulations)

Space servicesSection V – Radio astronomy in the shielded zone of the Moon

22.22 § 8 1) In the shielded zone of the Moon31 emissions causing harmful inter ference to radio astronomy observations32 and to other users of passive services shall be prohibited in the entire frequency spectrum except in the following bands:

22.23 a) the frequency bands allocated to the space research service using active sensors;

22.24 b) the frequency bands allocated to the space operation service, the Earth exploration-satellite service using active sensors, and the radiolocation service using stations on spaceborne platforms, which are required for the support of space research, as well as for radiocommunications and space research transmissions within the lunar shielded zone.

22.25 2) In frequency bands in which emissions are not prohibited by Nos. 22.22 to 22.24, radio astronomy observations and passive space research in the shielded zone of the Moon may be protected from harmful interference by agreement between administrations concerned.

22.22.1 The shielded zone of the Moon comprises the area of the Moon’s surface and an adjacent volume of space which are shielded from emissions originating within a distance of 100 000 km from the centre of the Earth.

32 22.22.2 The level of harmful interference is determined by agreement between the administrations concerned, with the guidance of the relevant ITU-R Recommendations.

Good “news” …The Moon is radio protected!

• The back side of the moon is declared as a radio protected site within the ITU Radio Regulations

– The IT Radio Regulations are an international treaty within the UN.

– Details are specified in a published ITU Recommendation (this is a non-mandatory recommendation, but is typically adhered to).

Radio astronomy on the moon has been a long-standing goal, protected by international treaties!

Steps need to be taken to protect the pristine and clean nature of the moon.

Lunar communication on the far side needs to be radio quiet.

Sources responsible for reionization

Luminous AGN: No

Star forming galaxies: maybe -- dwarf galaxies (Bowens05; Yan04)?

mini-QSOs -- unlikely (soft Xray BG; Dijkstra04)

Decaying sterile neutrinos -- unlikely (various BGs; Mapelli05)

Pop III stars z>10? midIR BG (Kashlinsky05), but trecomb < tuniv at z~10

GP => Reionization occurs in ‘twilight zone’, opaque for obs <0.9 m

Needed for reion.

Radio galaxy spectra: Smooth powerlaw (eg. Cygnus A)

Tsiolkovsky crater

(100 km diameter)

20°S 129°E

Apollo 15

Tsiolkovsky crater