Ionized

Neutral

Reionized

Update: HI 21cm cosmic reionization experimentsChris Carilli (NRAO) MPIA July 2008

• Last phase of cosmic evolution to be explored

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

• GP + CMBpol => z ~ 7 to 11

HI 21cm Tomography of IGM: freq ~ 100 to 200 MHz

z=12

9

7.6

)1()10

1)((008.0 2/1 δτ +

+= HI

S

CMB fz

TT

• Large scale structure: f(HI) , Temp (K, CMB, Spin)

• Advantages: 3D, optically thin, dominant baryon component

• Tomography requires SKA

TB(2’) = 10’s mK

SKA rms(100hr) = 4mK

LOFAR rms (1000hr) = 80mK

Furlanetto, Zaldarriaga + 2004

0.5Mpc

Global (‘all sky’) reionization signature

Signal ~ 20mK < 1e-4 sky

Possible higher z absorption signal via Lya coupling of Ts -- TK due to first luminous objects

Feedback in Galaxy formation

No Feedback

Furlanetto, Oh, Briggs 06

•21cm forest•Radio GP

Absorption

QSO Cosmic Stromgren Spheres

5Mpc

LOFAR

SKA

Signal ~ 0.5mJyrms(MWA) ~ 0.1mJy

10%

Pathfinders: 1% to 10% SKAMWA (MIT/CfA/ANU)

32 Tile array deployment in WA 2009

21CMA (China): 10,000 Dipole array working in Western China 2008

Site Type Freq MHz Area m2 Goal Date

GMRT India Parabola 150-165 4e4 CSS 2009

21CMA China Dipole 70-200 1e5 PS 2008

PAPER GB/Oz/SA? Dipole 110-200 5e3 PS/CSS 2009

MWAdemo Oz Aperture array

80-300 1e4 PS/CSS 2009

LOFAR NL Aperture array

115-240 1e5 PS/CSS 2010

Challenge: Low frequency foreground – hot, confused sky

Eberg 408 MHz Image (Haslam + 1982)

•Coldest regions: T ~ 100z)^-2.6 K

•Highly ‘confused’: 1 source/deg^2 with S140 > 1 Jy

• Synch. smooth ~ 100MHz vs. 21cm lines ~ 1 MHz

0.5 to 5.0 GHz

•Frequency differencing with MHz channels doesn’t work well for far-out sidelobes due to chromatic aberration.

•Require < 0.2% calibration errors each day to reach thermal noise

1MHz separation

Rphys ~ 1.7Mpc

5MHz separation

10o

Datta+ 09

0.1% 1%

Challenge: Interference

100 MHz z=13

200 MHz z=6

Solutions -- RFI Mitigation (Ellingson06)

Digital filtering

Beam nulling

Real-time ‘reference beam’

LOCATION!

Aircraft

Orbcom

TV

VLA-VHF: 180 – 200 MHz Prime focus X-dipole 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

Detect CSS by 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

Chippendale & Beresford 2007

Precisions Array to Probe the Epoch of Reionization (PAPER)PI Backer, Bradley

Western Australian deployment in 2008

• Optimize for reionization PS/CSS

• FoV ~ 30deg, short baselines < 0.6km

• Staged engineering: GB06 8 stations WA09 32 stations

PAPER: Staged Engineering• Broad band sleeve dipole + flaps

• FPGA-based ‘pocket correlator’ from Berkeley wireless lab

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

100MHz 200MHz

BEE2: 5 FPGAs, 500 Gops/s

Beam response

CygA 1e4Jy

PAPER/WA -- 4 Ant, July 2007

RMS ~ 1Jy; DNR ~ 1e4

Parsons et al. 2009

120MHz 180MHz

Destination: Moon!

RAE2 1973

No interference

No ionosphere

Only place to study ‘dark ages’

Recognized as top astronomy priority for NASA initiative to return Man to Moon (Livio 2007)

NASA concept study: DALI/LAMA (NRL + MIT + NRAO…)

10MHz

J. Burns PI Colorado

TIDs – ‘fuzz-out’ sources

‘Isoplanatic patch’ = few deg = few km

Phase variation proportional to ^2

Solution:

Reionization requires only short baselines (< 1km)

Wide field ‘rubber screen’ phase self-calibration

Challenge II: Ionospheric phase errors – varying e- content

Virgo A VLA 74 MHz Lane + 02

15’

Say, its only a PAPER moonSailing over a cardboard seaBut it wouldn't be make-believeIf you believed in me