1 100 SKA stations (2020 ) Projets avec SKA

2 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

3 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

4 Project Time-line  Proposed sites: Argentina, Australia, China, South Africa Site ranking/description: 09/2006  Proposed concepts: phased array, large parabolas/cylinders, LNSD Concept 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: 2010 Construction of full-scale SKA :

5 Field of view At least 1 square degree Goal sq deg. Point source sensitivity of 10 nano-Jy in 8hours

6 Multi-Beam

7 EMBRACE  THEA array of 1 sq m, built at ASTRON Beamforming system below, to form 2 fields of view  Schematic view of EMBRACE demonstrator (fibre network) 100 m 2 Electronic MultiBeam Radio Astronomy ConcEpt

8 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 w 0 and w 1 to 1% accuracy KP 4 - Galaxy evolution and cosmology

9 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 deg 2 ) HI Line surveys

10 Dark energy measuring machine: I-Wiggles Billion galaxies at z ~1-2 II- Weak Shear 10 billion galaxies, 10 nanoJy

11 SNAP and SKA compared Resolution and Sky area 2000 SN 0.1<z<1.7

12 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 5, detection rate like ALMA for high transitions unobscured views of unprecedented numbers of AGNs etc. KP 5 - Probing the dark ages

13 Possible double re-ionization scenario Furlanetto et al 2004

14 Simulation of Reionization log(f_HI) Ionizing - Background log(gas density) log T Gnedin (2000) z=11.5 z=7 z=4.9

15 When is the re-ionisation completed? Mass Volume Gnedin 2004 Different ionisation histories With the same z rei OTVET method for RT

16 Signal from the EoR period, at 21cm Gnedin & Shaver x20 °, Scale in T(mK)

17 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.

18 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…

19 LOFAR: precursor of SKA New generation of radio-telescopes, with phased arrays  > 1.2m Low-cost antennae:15000 over 100km, then over 350km Cost 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

20 In the middle of band 1 arsec resolution 100 sqdeg field 1mJy sensitivity Demonstration antennae are operationnal Construction begins end of spiral arms with compact core Will serve to learn how to observe with SKA

21 Timeline