Hydrogen Epoch of Reionization Array

(HERA)DESCRIPTION AND INITIAL COMMISSIONING RESULTS

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Bojan Nikolic on behalf of the HERA collaboration

WITH PARTICULAR THANKS TO C. CARILLI , D. DEBOER AND K. GALE-SIDES FOR FIGURES/SLIDES

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HERA Collaboration

FUNDING BODIES ACADEMIC PARTNERS PI: A. PARSONS

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Science Driver: Cosmic Reionisation

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𝑓 H I ~ 0

z=1100400 kyr

z ~ 6 to 300.3 to 1 Gyr

z < 61Gyr to 13.7Gyr

Reionisation

Figure credit: A. Loeb

𝑓 H I ~ 1 𝑓 H I ~ 10−5

HERA Site: Karoo Radio Astronomy Reserve, SA

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HERA Site: Karoo Radio Astronomy Reserve, SA

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HERA Site: Karoo Radio Astronomy Reserve, SA

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HERA: 351 x 14m parabolic transit antennas, 50 to 250MHzCollecting area of Arecibo but 450x Field of View, configured for very high number of redundant & short spacings

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HERA Description•HERA is one of the four official SKA Precursors (MWA, ASKAP, MeerKAT & HERA)

• Design optimised for EoR: frequency & bandwidth, high sensitivity, delay spectrum response

•Highly compact & redundant configuration

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Focus on the Delay Spectrum▪Blue solid lines: example wavenumbers sampled in delay only

▪Black solid lines: example wavenumbers sampled in uv only

▪Green shaded region: part of the wavenumber-redshift space on which HERA will initially focus

HERA focuses on short spacings and the frequency/delay measurement

Greatly reduces the effect of smooth spectrum foregrounds

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See DeBoer (2016) arXiv:1606.07473v2

Initial Focus for

HERA

An Aside: The “Wedge"

Spatial wavenumberk = kx + ky + kz

k = kx + ky (baseline)

k = kz (delay)

HERA Block Diagram

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Monitor & Control

Feed Analog Digital Real Time Processor

Librarian

Power and Fibre Post Processing

Cambridge is contributing to the design:

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Monitor & Control

Feed Analog Digital Real Time Processor

Librarian

Power and Fibre Post Processing

Array FoVdeg2

Area m2

Type PS S/N*FG Avoidance

PS S/N*FG Removal

FWHM150

arcminStartdate

PAPER-128 1600 1200 Dipole 1.2 4.8 23 2013

MWA-128 300 3600 Tile 0.6 6.4 10 2013

LOFAR 25 37000 Tile 1.4 17 5 2013

HERA-331 64 54000 Dish 23 91 20 2018

SKA1 Low 30 420000 Tile 13 140 5 2021+

*Power spectrum sensitivity to ‘vanilla’ model: Pober 2014, ‘21cmSense’ cosmology calculator

PAPER - SA MWA - Aus

Reionisation experiments compared

Timeline

Kavli III

HERA COMISSIONINGINITIAL RESULTS WITH SKY CALIBRATION AND CLOSURE PHASE

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Summary of commissioning analysis work at Cambridge

All based on the HERA-19 data acquired during 2016 and done in collaboration with NRAO

1. Sky-based calibration and imaging

2. Closure-phase analysis

3. Processing strategy using CASA

Lots of other activities wider in the project

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HERA first image: Galactic Centre (Nikolic/Carilli)

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18ants1.2o resDNR ~ 200

PAPER 64 imaging, 20’ res

PB

See: Nikolic, Carilli & Sims 2016, HERA Memo 22

Closure Phase Analysis

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A calibration-independent measure of non-redundancyIndicates around 2% non- redundancy

See Carilli & Nikolic, HERA memo forthcoming

Task-based parallelisation of CASACross over of ideas from SKA Science Data Processor design effort (dataflow execution)

CASA task-based distribution & parallelisation

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Efficient computing scale-out to deal with ~100s TB of raw data

Seehttp://www.mrao.cam.ac.uk/~bn204/publications/2017/2017-08-

casaswift.pdf

SummaryHERA is:

•SKA Precursor with major UK involvement

•Addresses EoR one of the key SKA Science drivers

•Taking data now, being built-out rapidly to 100 antennas by end of year

•From end of the year to full SKA1-Low operations, HERA is expected to be the most sensitive telescope to the redshifted 21cm EoR signal

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