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THE NEED FOR A SQUARE KILOMETER ARRAY

THE NEED FOR A SQUARE KILOMETER ARRAY. What is the SKA? Why build the SKA? Science Goals & Payoffs Configurations, Modes and Sites Development Plan (International, US). For the US SKA Consortium Jim Cordes, Cornell University CfA talk, 3 April 2001. The SKA Concept.

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THE NEED FOR A SQUARE KILOMETER ARRAY

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  1. THE NEED FOR A SQUARE KILOMETER ARRAY • What is the SKA? • Why build the SKA? • Science Goals & Payoffs • Configurations, Modes and Sites • Development Plan (International, US) For the US SKA Consortium Jim Cordes, Cornell University CfA talk, 3 April 2001

  2. The SKA Concept Initiated in early 1990s through considerations of: • high redshift science • needed sensitivity (Ae / Tsys) • coverage of obs. phase space for many science goals • complementarity with other  (LOFAR, EVLA, ATA, ALMA, LSST, VLT, NGST, EXIST, GLAST, CELT, OWL . . . ) • advances in digital hardware & RF devices • mitigation of RFI  innovation needed

  3. China KARST Canadian aerostat US Large N Australian Luneburg Lenses Dutch fixed planar array Current Concepts (cf. Allen Telescope Array, Extended VLA) (cf. LOFAR = Low Freqency Array)

  4. Photos: R.N. Manchester

  5. Canadian Aerostat & Paraboloid

  6. China KARST Canadian aerostat US Large N Australian Luneburg Lenses Dutch fixed planar array Current Concepts (cf. Allen Telescope Array, Extended VLA) (cf. LOFAR = Low Freqency Array)

  7. Previous Actions • 1993 URSI Large Telescope Working Group • 1997 International Memo. of Agreement • 1997- Workshops on science & technology • 1999 US SKA Consortium established to mobilize US participation • late 90s Endorsements by review panels (Australia, Canada, China, Eur. Union) • 1999- Presentations to Decadal Review Panel (Jackie Hewitt)

  8. Astronomy & Astrophysics in the New Millenium Recommends: “…that a program be established to plan and develop technology for the Square Kilometer Array, an international centimeter wavelength radio telescope for the second decade of the century.”

  9. Current Baseline Specifications

  10. Figures of merit for current telescope developments SKA VLBI Circle radius = target or best Arrows: Blue = current best Cyan = target SKA SKA SKA BATSE GLAST VLTI, KECKI GLAST CELT,OWL GLAST

  11. Key Science Areas • High Redshift Universe • Transient Universe • Galactic Census • Solar System Inventories Science document (c. 1998): Science with the SKA: A Next Generation World Radio Observatory (AR Taylor, R Braun) http://www.skatelescope.org/ska_science.shtml

  12. The High-z Universe • End of the Dark Ages: z ~ 6 - 20 (?) • Resolution: 0.1 arcsec ~ 1 kpc (z=1) • Identify: • pregalactic structures • competition between mergers and galaxy winds (size, mass distributions) • distribution of luminous matter w.r.t. dark matter potentials

  13. The High-z Universe Detectability: 1. 21-cm HI out of equilibrium with CBR 2. Earliest star bursts (synchrotron) 3. Early CO (z > 4.2 for 10, 8.4 for 2 1) HI Column Densities: 1017 cm-2 Typical L* galaxy to z~2  ~ 105 galaxies / deg2 rotation curves to z~1 CO: L* to z~20 (should they exist!)

  14. The High-z Universe (2) Other High-z Science: • Large scale structure studies • Gravitational lensing of large samples • Weak-lensing studies of dark matter dist’ns. • Tests of the unified AGN model and routine polarization mapping (m.a.s. and larger) • Megamasers to z~2 (OH) and z~0.15 (H2O) to track merger activity.

  15. TRANSIENT SOURCES Sky Surveys: The X-and--ray sky has been monitored highly successfully with wide FOV detectors (e.g. RXTE/ASM, CGRO/BATSE). The transient radio sky (e.g. t < 1 month) is largely unexplored. New objects/phenomena are likely to be discovered as well as the predictable classes of objects.

  16. TRANSIENT SOURCES (2) • TARGET OBJECTS: • Neutron star magnetospheres • Accretion disk transients (NS, blackholes) • Supernovae • Gamma-ray burst sources • Brown dwarf flares (astro-ph/0102301) • Planetary magnetospheres & atmospheres • Maser spikes • ETI

  17. TRANSIENT SOURCES (3) • Certain detections: • Analogs to giant pulses from the Crab pulsar out to ~5 Mpc • Flares from brown dwarfs out to at least 100 pc. • GRB afterglows to 1 µJy in 10 hours at 10 . • Possibilities: • -ray quiet bursts and afterglows? • Intermittent ETI signals? • Planetary flares?

  18. OBSERVABLE DISTANCES OF CRAB PULSAR’S GIANT PULSES

  19. Methods with the SKA I. Target individual SNRs in galaxies to 5-10 Mpc II. Blind Surveys: trade FOV against gain by multiplexing SKA into subarrays. III. In all cases, exploit coincidence tests to ferret out RFI

  20. Milky Way Census Targets: Molecular cloud regions YSOs, jets Main sequence stars (thermal!) Evolving & evolved stars Full Galactic Census: microquasars radio pulsars (P-DM searches, SKA-VLBI astrometry) SNR-NS connections (SGRs, magnetars, etc.)

  21. Surveys with Parkes, Arecibo & GBT. Simulated & actual Yield ~ 2000 pulsars.

  22. SKA pulsar survey 600 s per beam ~104 psr’s

  23. Pulsar Yield Up to 104 pulsars (~105 in MW, 20% beaming) NS-NS binaries (~ 100, merger rate) NS-BH binaries (?) Planets, magnetars etc. Pulsars as probes of entire Galaxy: • spiral arms • pulsar locations vs. age • electron density map (all large HII regions sampled) • magnetic field map from Faraday rotation • turbulence map for WIM (warm ionized medium)

  24. Solar System Inventories:KBOs & Tracking NEOs • Thermal detection of KBOs out to 100 AU (> 350 km)  SKA needs to go to ~20 GHz • Orbital elements of NEOs (>200m): SKA as receiver element of bistatic radar configuration

  25. The Main Technology Challenges 1. Cost per unit Ae / Tsys • Arecibo (~$150M)  $3G • EVLA I (~$200M)  $15G  Need to reduce costs to < $1G ( 5 to 15)

  26. The Main Technology Challenges 2. Fully digital solutions to: • sampling • beam forming • RFI rejection • signal processing • real time • post processing  Concept studies + Moore’s Law

  27. The Main Technology Challenges 3. Promoting & Maintaining radio-quiet sites.  Campaigning & working with governmental and international agencies and industry.

  28. The Main Technology Challenges 4. Operations & Data Management of a highly multiplexed, wide-bandwidth instrument.  Automated operations, large-scale data mining and storage.

  29. Future Timeline (1) • 2001 White Paper to NSF for technology development ( 2006) • 2002 Prioritized science goals (international) Design requirements SKA Management Plan established • 2003 Strawman designs Site requirements • 2005 Design Choice Site selection

  30. Future Timeline (2) • 2006-2010: Prototype array(s) • 2010 SKA construction begins • 2015 Completion

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