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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
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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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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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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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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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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