Epoch of Reionization

•last phase of cosmic evolution to be explored

•bench-mark in cosmic structure formation indicating the first luminous structures

Cosmic reionization and other lunar radio studies

Chris Carilli (NRAO)

z=5.80

z=5.82

z=5.99

z=6.28

Large scale CMB pol: zEoR=11+/-3

First observational constraints on cosmic reionization

T

TE

EE

Gunn-Peterson Effect: zEoR >= 6

Fan

Page

TT

Current observations: zEoR = 14 to 6 (Fan, Carilli, Keating 2006)

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

GP => occurs in ‘twilight zone’, opaque _obs< 0.9 um

Limited Diagnostics

•GP: Ly > 1e4 for f(HI)> 1e-3 => low f(HI)

•CMB pol = integral measure of e => high f(HI)

Studying the pristine IGM into the EOR, and beyond: redshifted HI 21cm observations in range 30 – 200 MHz

SKA goal: Jy at 200 MHz Large scale structure: density, f(HI), T_spin

1e12Mo

1e9Mo

Lunar Advantage I: Interference

100 MHz z=13

200 MHz z=6

Destination: Moon!RAE-2 1973

• Ionospheric Opacity: p ~1 to 10 MHz

TIDs – ‘fuzz-out’ sources

‘Isoplanatic patch’ = few deg = few km

Phase variation proportional to ^-2

Solution: ‘Rubber screen’ phase self-calibration

Virgo A VLA 74 MHz Lane + 02

Lunar Advantage II: Ionospheric phase distortions

Remaining challenge: Low frequency backgroundColdest regions: T = 100z)^-2.7 K

Highly ‘confused’: 3 sources/arcmin^2 with S_0.2 > 0.1 mJy

Eberg 408 MHz Image (Haslam82)

Solution: fitting in the spectral domain

HI 21cm Tomography of IGM Zaldarriaga + 2003

z=12 9 7.6

T_B(2’) = 10’s mK => DNR > 1e5

LOFAR rms (1000hr) = 80mK

SKA rms(100hr) = 4mK

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 (IGM) after reionization = Ly alpha forest ( <= 10))

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

• Expect 0.05 to 0.5 sources/deg^2 at z> 6 with S_151 > 6 mJy

z=12 z=8

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

S230 = 0.5Jy;

rms (20km/s) = 5 mJy

z(CO)

0924-2201 8GHz

1”

Van Breugel et al.

RFI = 20 kiloJy !

N(HI) < 1e20 (Ts/100) cm^-2

Only direct probe of host galaxy: dust, molecular gas

Coeval starburst/AGN: SFR ~ 1e3 Mo/yr

2e10 Mo of molecular gas = fuel for star formation

Early enrichment of heavy elements/dust: zsf > 8

J1148 VLA CO 3-2

2.5”

IRAM

Molecular gas + fine structure lines: J1148+5251 z=6.42

tuniv=0.87 Gyr[CII]

CO 6-5

1148+5251

Cosmic Stromgren Spheres

• 1148+5251: Accurate z_host from CO: z=6.419+/0.001

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

•‘time bounded’ Stromgren sphere: R = 4.7 Mpc

• f(HI) = 1e-5 R^-3 (tqso/1e7) yrs

White et al. 2003

Loeb & Rybicki 2000

Largest ‘bubbles’ at end of reionization

HI imaging of Cosmic Stromgren spheres around z > 6 QSOs

0.5 mJy

LOFAR ‘observation’: 0.5 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

VLA-VHF: 180 – 200 MHz Prime focus X-dipole Greenhill, Blundell (SAO Rx lab); 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

Project abandoned: Digital TV

KNMD Ch 9

150W at 100km

• Focus: EoR signal (power spec, CSS, abs)

• Very wide field: full cross correlation of all dipoles

• Staged engineering approach: GB Mileura07

PAPER: First images/spectra

Cygnus A

1e4Jy

Cas A 1e4Jy

3C392

200Jy

3C348

400 Jy

140MHz180MHz

Very low frequency (<30MHz): pre-reionization HI signal

Lunar imperative; eg. Baryon Oscillations (Barkana & Loeb)

Very difficult to detect

Signal: 10 arcmin, 10mk => S_30MHz = 0.02 mJy

SKA sens in 1000hrs:

T= 100(/200 MHz)^-2.7 K

= 20000K at 30MHz =>

rms = 0.2 mJy

Need > 10 SKAs

Need DNR > 1e6

z=50

z=150

Lunar VLF science: 0.1 to 10 MHz

Advantages

• Between Earth’s ionospheric cutoff and heliosphere/Galactic free-free cutoff

•Blocked from earth auroral emission

•RFI Protected ‘volume’ (ITU 22.22 – 22.25)

•Easy deployment: Javelins, Roll-out, Rover, Inflatables

•Easy maintenance: ‘cheap’, high tolerance electronics, no moving parts

VLF science

Coronal Mass Ejections and space weather ‘early warning system’ – passive + remote sensing (Bastian)

Extrasolar planetary radio bursts (Lazio)

~ 1 – 100 MHz

S ~ 0.1 – 100 mJy

Array of lunar sensors

Cherenkov radiation from neutrinos in lunar regolith

Geophones: lunar seismology

•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

ALMA on the moon: Why?

• No Troposphere – phase and opacity, eg. 650GHz (350m): Trx = 125K, =0.5, Tsky=150K => Same sensitivity with 16 ants vs. 64

• No wind, less gravity: lighter dishes

• Stable platform for interferometry

Why not?• Cryogenics: need 4K (HeII) for SIS

• Power: ALMA = 5-8 MW

Radio astronomy – Probing Cosmic Reionization

•First constraints: GP, CMBpol=> zEoR = 6 to 14

• HI 21cm: most direct probe of reionization

•Low freq pathfinders:

All-sky, PS, CSS, Abs.

•SKA: imaging of IGM

• Lunar advantages:

Interference

No ionosphere

Relatively ‘easy’

European Aeronautic Defence and Space Corporation/ASTRON (Falcke)

• Payload = 1000 kg (Ariane V)

• 100 antennas at 1-10 MHz ~ 1/10 SKA

END

All sky: SI deviations = 0.001

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

10’ FoV; SKA 1000hrs

Power spectral analysis: Fourier analysis in 3D – different symmetries in freq space (ie. Different spectral chan-chan correlation)

Freq

Signal Foreground

Solution – RFI mitigation: location, location location…

100 people km^-2

1 km^-2

0.01 km^-2

‘Pathfinders’: PAST, LOFAR, MWA, VLA-VHF, …

MWA prototype (MIT/ANU)

LOFAR (NL)

PAST (CMU/China) VLA-VHF (CfA/NRAO)

Main Experiment: Cosmic Stromgren spheres around z=6 to 6.5 SDSS QSOs (Wyithe & Loeb 2004)

VLA-VHF 190MHz 250hrs

15’

20 f(HI) mK

0.50+/-0.12 mJy

VLA spectral/spatial resolution well matched to expected signal: 7’, 1000 km/s

Set first hard limits on f(HI) at end of cosmic reionization (f(HI) < 0.3)

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

LOFAR Hi-Band Antenna (110-240 MHz)LOFAR Hi-Band Antenna (110-240 MHz)

Westerbork Westerbork Radio Radio

ObservatoryObservatory

Paradigm shift: from steel to silicon.

Past: a lot of steel to focus radiation on a single electronic receiver

Future: many digital receivers and massive data processing synthesize virtual telescope in software

ARTICLE 22(ITU Radio Regulations)

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

Moon22.22 § 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.

Lunar LOFAR:Distributed array of radio sensors

Start with N=100 antennas Collecting area:

Aeff=N2/8 (3 MHz; ~100 m)Aeff~ 0.125 km2

(17 football fields or ~400 m dish) First prototype phase:

Antennas, power, computers, communication, dispatcher

Weight ~1000 kg (payload) Needs only one Ariane V launch

Separation D = 1 km → 1000 km Resolution (/D):

~1.6° (D=1 km, 10 MHz) ~6’’ (D=1000 km, 10

MHz) ~ 1’ (D=1000 km, 1

MHz )• Remote antennas are added later

Ionosphere Opacity:

p ~ 1 to 10MHz

Phase errors

TIDs – ‘fuzz-out’ sources

‘Isoplanatic patch’ = few deg = few km

Phase variation proportional to wavelength^2

Global reionization signature in low frequency HI spectra

(Gnedin & Shaver 2003)

double

fast21cm ‘deviations’ at

1e-4 wrt foreground

Spectral index deviations of 0.001