1. The Square Kilometre Array A technology-enabled approach to `Hubble Volume’ Redshift Surveys A phased roll-out of an array that has seriously started (that will involve phased arrays).

2. Will only discuss the Cosmology & Galaxy Evolution Key Science Project
See Carilli & Rawlings (2004) for everything else:
Pulsars, GR & Gravitational waves
Magnetic Universe
Epoch of Reionisation
Cradle of Life

3. Whether Dark Energy is Einstein’s Cosmological Constant
Some important things that need both Planck and ‘Hubble Volume’ Redshift Surveys
Whether Dark Energy is Einstein’s
Cosmological Constant
The neutrino (Hot Dark Matter) mass
Whether the geometry of the Universe is precisely Spatially Flat (see Knox 2006)

6. ? ? ? ? ?

7. Need Redshift Resolution
Geometric effects give systematic patterns in z for a given w
Beware non-linearity/bias effects, at high k and low z
Percival’s 2 evidence for w<-1 very exciting

8. Need multiple measures of P(k)
mn= 0.05 eV
mn= 0.25 eV
mn=0.5 eV
Z = 0.5 – 1
Z = 1.5 – 2
Z = 1 – 1.5
Abdalla & Rawlings (2007)

9. Some good things about radio methods
Time coherence of electric field means 3D redshift surveys for free: photometric surveys lose information on k-modes parallel to the line-of-sight: loss of effective cosmic volume; loss of velocity-space distortion information that greatly aids marginalisation over galaxy bias
Spatial coherence of electric field means a growing array can ‘zoom in’ to get direct (`rotation curve’) information on host dark- matter haloes
Higher redshift maps to lower frequency, HI at 1.4 GHz at z=0 to ~300 MHz at z~4, collecting area becomes cheaper

10. State-of-the-art
Verheijen et al. get ~10 objects to z~0.2 in ~200 WSRT: Abell 963/2192

11. Technology and the Phased Approach
Cosmic volume ~ (time) x (FOV) x (A/T)2 for radio HI
If we rely on time, errors on P(k) improve by an order of magnitude every 100 years!
Technology I: increase dish FOV by ~100 and `dedicate’ array, ~105 galaxies to z~0.2 (1% SKA pathfinders ~2010)
Technology 2: increase A/T by ~10. ~107 galaxies over 20,000 deg2 to z~0.75 (10% SKA in dishes ~2015)
Technology 3: Change in technology ( MHz). Further increase in A/T and FOV. ~109 galaxies to z~2 (100% SKA in aperture arrays ~2020).
Technology 4: Benefit from increased processing power as you integrate ( MHz). >1010 galaxies to z~4 ( )

12. Phased and `All Digital’ Aperture Arrays
Simulation by Michael Kramer (Manchester)
Recent D&C exercise delivers 250 deg2 FOV!

13. Picture & Joke Credit: Paul Alexander
The SKA on one slide
processor
Picture & Joke Credit: Paul Alexander

14. SKADS Universe in a Box
Obreshkow et al, in prep. and Wilman et al, in prep.

15. Uncertain HI Evolution

16. Milestone 1: ~1% SKA (~2010)
in ~100 days >105 galaxies: an ~1000 deg2 survey to z~0.2;
gives P(k) and hence bias

17. Milestone 2: ~1% SKA+FMOS/AA
‘Radio stacking’ on optical/near-IR redshifts out to z~1
Wiggle-z: ~400 targets per deg2 over large (~30 deg2) patches: √12000~100 gain on star-forming subset of galaxies
FMOS: 12,000 deg-2, √12000~100 gain on ALL galaxies in deg2 patches
Should provide statistical detections of HI emission to z~1 (alongside HI absorption experiments to higher z)

18. Milestone 3: ~10% SKA (~2015)
Dishes: >107 galaxies over ~20,000 deg2 to z~0.75 (or 800 MHz); multiple P(k) to z~0.35, stacked analyses to z~2
Likely to be similar cosmic volumes to optical redshift surveys (e.g WFMOS: combination very powerful for studying galaxy evolution and bias).
Survey Volumes then grow, at best, linearly with t, hence P(k) accuracy grows as t0.5

19. Milestone 4: SKA (~2020)
In ~100 days, phased arrays deliver >109 galaxies over ~20,000 deg2 to z~2 (and multiple P(k) to at least z~1)

20. SKA(100 days)+Planck

21. Measurement of Neutrino masses and hierarchies
Abdalla & Rawlings (2007)
If Smn is ~0.05 eV, SKA+Planck sufficient and necessary to measure it, and hierarchy must be normal
If Smn > 0.25 eV, direct measurement of Nn too!
With particle physics experiments, prospect of evidence for sterile neutrinos

22. SPARSE AA CRITICALLY- DISHES SAMPLED AA
Milestone 5: SKA
~300 MHz: HI at z~4
Aeff
~800 MHz: HI at z~0.75: ~day with dish-SKA to get multiple P(k): perfect because few x 365~20,000/30
~500 MHz: HI at z~2: ~month with the AA-SKA to get multiple P(k): perfect because 10x12~20,000/250)
SPARSE AA CRITICALLY- DISHES SAMPLED AA
Frequency
Collecting area below 500 MHz rises as (1+z)2 for sparse arrays, but only worth going to z~4 because of sky temperature (Braun 2006)
Using multi-beaming to ‘shape’ FOV a (1+z)4 gives ~constant mapping speed, and a plausible FOV at the lowest frequency

23. Why? Curvature
z~2-4 ruler z~1000 ruler

24. There are other strategies
Gravitational lensing (e.g. LSST, JDEM, DUNE, SKA), Supernovae (e.g. JDEM) etc
Overcoming systematics is the key: P(k)/BAO method seems to be accepted to be the cleanest, but get all measures of growth/geometry!
For large-volume P(k)/BAO: brute-force replication is plausible or space (ADEPT?)