1 100 SKA stations (2020)

Projets avec SKA

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Telescope

Project (~2020) for a giant radiotelescope in the centimetre-metre range• one square kilometre collecting surface 100 x more sensitive than present radio telescopes for spectral line observations 1000 x more sensitive than present radio telescopes for continuum observations• frequencies: 0.15 – 25 GHz ( 1.2cm – 2m)• field of view: 1 ( 100?) square degrees at 21 cm / 1.4 GHz 8 independent fields of view• angular resolution: 0.01 arcsec at 21 cm / 1.4 GHz 100 ‘stations’ of 100m diameter, baselines up to ~ 3000 km

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Extra-galactic Key Projects

KP-4 Galaxy evolution and cosmology (surveys in HI at z up to 2, CO and continuum; nature of dark energy)

KP-5 Probing the dark ages (Epoch of Reionisation) (HI in emission/absorption, CO, continuum)

Wiggles, for tackling dark energy

reionization

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Project Time-line

Proposed sites: Argentina, Australia, China, South AfricaSite ranking/description: 09/2006Proposed concepts: phased array, large parabolas/cylinders, LNSDConcept selection: 2009

Design studies under way: AUS, RSA; CAN, CHN; USA; Europe (EC FP6 SKA Design Study; 10 MEUR EC)French participation:

• Construction of EMBRACE, a demonstrator of the european phased array SKA concept (at Westerbork and Nançay in 2007)• R&D towards the choice of this concept for the SKA• Scientific modeling (cosmology – Horizon team)

Start construction 100,000 m2 SKA pathfinder on the site: 2010Construction of full-scale SKA : 2014-2020

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Field of view

At least 1 square degreeGoal 50-100 sq deg.

Point source sensitivity of 10 nano-Jy in 8hours

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Multi-Beam

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EMBRACE

THEA array of 1 sq m, built at ASTRONBeamforming system below, to form 2 fields of view Schematic view of EMBRACE demonstrator (fibre network) 100 m2

Electronic MultiBeam Radio Astronomy ConcEpt

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1- HI line surveys

All-sky survey would contain a billion galaxies out to z~1.5

Galaxy evolution studies using the most abundant element

2- ‘Dark Energy-measuring-machine’

- acoustic peaks in baryons as function of z

- weak gravitational lensing in large fields

Measure DE parameters w0 and w1 to 1% accuracy

KP 4 - Galaxy evolution and cosmology

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HI surveys

main reservoir of star formation, galaxy evolution stage

tracer of DM in galaxies

various environments, groups, clusters, interactions

All-sky HI surveys presently out to z~0.04, no evolution information

SKA: All-sky HI survey is needed out to cosmological distances,

to distinguish between various evolution models

- All-sky survey would contain a billion galaxies out to z~1.5

- Deeper, targeted surveys ten million galaxies at 2.5<z<3.5

Feasible in 1 year if field-of-view large enough (>10 deg2)

HI Line surveys

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Dark energy measuring machine: I-Wiggles

Billion galaxies at z ~1-2

II- Weak Shear10 billion galaxies, 10 nanoJy

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SNAP and SKA compared

Resolution andSky area

2000 SN 0.1<z<1.7

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1- Epoch of Reionisation (EoR) occurs at z~6 (?)

HI line observations at high z to study ionisation as function of z

HI emission tomography

HI absorption towards first radio-loud objects

2- First luminous objects: CO line and continuum detections

at <20 GHz: CO(1-0) at z>5, detection rate like ALMA for high transitions

unobscured views of unprecedented numbers of AGNs etc.

KP 5 - Probing the dark ages

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Possible double re-ionization scenario

Furlanetto et al 2004

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Simulation of Reionization

log(f_HI)

Ionizing - Background

log(gas density)log TGnedin (2000)

z=11.5

z=7 z=4.9

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When is the re-ionisation completed?

Mass

Volume

Gnedin 2004

Different ionisation historiesWith the same zrei

OTVET method for RT

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Signal from the EoR period, at 21cm

Gnedin & Shaver 2004

20x20 °, Scale in T(mK)

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Probing the dark age

Problems

• The intensity of neutral hydrogen at high redshifts is 100 to 1000 times smaller than foreground sources.

• Incomplete modeling available for foreground sources in power spectra and evolution.

• need to remove the signals from brighter sources– Radio Galaxies– Radio Relics Synchrotron Emission– Radio Halos Synchrotron Emission– Free-free and line emission from the interstellar medium

•Use redshifted 21 cm emission to find the tomography

of neutral hydrogen.

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Removal of foregrounds

Final angular correlation function derived from calculations, observations, and lots of simulations with several assumptions (even on emission of stars!)

The 21 cm line is much weaker than several of the other signals…however with processes for data analysis and simulations, it might be possible to meet the challenge…

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LOFAR: precursor of SKA

New generation of radio-telescopes, with phased arrays > 1.2mLow-cost antennae:15000 over 100km, then 25000 over 350kmCost from electronics: A few Terabits/s, CPU 10s of Teraflops

Operated ny Netherlands: Astro, Geophysics, Agro-technologies« sensors » will use optic fiber arrays, and IBM processors

(1) Reionisation epoch (2) Large extra-galactic surveys : galaxy clusters, galaxies starbursts, with wide field(3) Transient phenomena (GRB, SN, LIGO...) instantaneous beam (4) UHE cosmic rays, recently detected with LOPES (LOFAR prototype station) (5) Pulsars

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In the middle of band1 arsec resolution100 sqdeg field1mJy sensitivity

Demonstration antennae areoperationnal

Construction begins end of 20055 spiral arms with compact core

Will serve to learn how to observe with SKA

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Timeline