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The Square Kilometer Array: Discovery and Timing of Pulsars Jim Cordes, Cornell University

 20. 50. The Square Kilometer Array: Discovery and Timing of Pulsars Jim Cordes, Cornell University. The SKA Project SKA science case Fundamental questions in physics, astrophysics and astrobiology Unprecedented capacity for discovery International and US activity

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The Square Kilometer Array: Discovery and Timing of Pulsars Jim Cordes, Cornell University

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  1. 20 50 The Square Kilometer Array: Discovery and Timing of PulsarsJim Cordes, Cornell University • The SKA Project • SKA science case • Fundamental questions in physics, astrophysics and astrobiology • Unprecedented capacity for discovery • International and US activity • The Pulsar Key Science Project • Massive census of the Galaxy, globular clusters and nearby galaxies • Generalized search algorithms • Issues for precision timing Jim Cordes: SKA: Pulsars and Gravity

  2. 20 50 SKA: What is It? • An array telescope that combines complete sampling of the time, frequency and spatial domains with a 20 to 50 increase in collecting area (~ 1 km2) over existing telescopes. • Frequency range 0.1 – 25 GHz (nominal) • Limited gains from reducing receiver noise or increasing bandwidth once the EVLA is finished • Innovative design needed to reduce cost • 106 meter2 ~ €1,000 per meter2 • c.f. existing arrays ~ €10,000 per meter2 • An international project from the start • International funding • Cost goal ~ € 1 billion • 17-country international consortium • Executive, engineering, science, siting, simulation groups • Timeline for construction extends to 2020 • Can be phased for different frequency ranges • Can do science as you build Jim Cordes: SKA: Pulsars and Gravity

  3. Science with the Square Kilometer Arrayedited by Chris CarilliSteve RawlingsSpecial issue of New Astronomy ReviewsVolume 48, December 2004, 979-1605(48 chapters) • Five key science projects • Discovery science • Enabling understanding in fundamental physics and origins Jim Cordes: SKA: Pulsars and Gravity

  4. Five Key Science Areas for the SKA Jim Cordes: SKA: Pulsars and Gravity

  5. Jim Cordes: SKA: Pulsars and Gravity

  6. Other References “Strong-field tests of gravity using pulsars and black holes,” Kramer et al. 2004 “Pulsars as tools for fundamental physics and astrophysics,” Cordes et al 2004 In Science with the Square Kilometer Array, Eds. C. Carilli and S. Rawlings (~50 articles) Available at www.skatelescope.org and on arXiv/astro-ph Jim Cordes: SKA: Pulsars and Gravity

  7. Surveys: past, present and future Jim Cordes: SKA: Pulsars and Gravity

  8. Was Einstein Right About Gravity?The SKA as a Pulsar/Gravity Machine • Relativistic binaries (NS-NS, NS-BH) for probing strong-field gravity • Orbit evolution + propagation effects of pulsars near Sgr A* • Millisecond pulsars < 1.5 ms (EOS) • MSPs suitable for gravitational wave detection • 100s of NS masses (vs. evolutionary path, EOS, etc) • Galactic tomography of electron density and magnetic field; definition of Milky Way’s spiral structure • Target classes for multiwavelength and non-EM studies (future gamma-ray missions, gravitational wave detectors) Millisecond Pulsars Relativistic Binaries Today Future Today Future SKA SKA Blue points: SKA simulation Black points: known pulsars only 6! ~104 pulsar detections Jim Cordes: SKA: Pulsars and Gravity

  9. High sensitivity: Large processing FOV , , t, pol , , t Combine Greater Sensitivity with Wide Field of View Processing The SKA combines a > 20 boost in sensitivity with unprecedented utilization of the field of view Jim Cordes: SKA: Pulsars and Gravity

  10. DM Frequency time time Pulsar Periodicity Search FFT each DM’s time series |FFT(f)| 1/P 2/P 3/P    Jim Cordes: SKA: Pulsars and Gravity

  11. The power of ALFA: I(, t, j) j=1,7 Jim Cordes: SKA: Pulsars and Gravity

  12. A pulsar found through its single-pulse emission, not its periodicity (c.f. Crab giant pulses). Algorithm: matched filtering in the DM-t plane. ALFA’s 7 beams provide powerful discrimination between celestial and RFI transients Jim Cordes: SKA: Pulsars and Gravity

  13. Comparison of maximum detectable distance vs. P and pulsar luminosity Jim Cordes: SKA: Pulsars and Gravity

  14. Jim Cordes: SKA: Pulsars and Gravity

  15. SKA Development in the US US Concept: Large-N/Small-D (LNSD) • The US SKA Consortium prepares whitepapers on the LNSD concept for consideration by the International SKA Steering Committee and also for a SW US high-frequency SKA site • Allen Telescope Array • Low-frequency arrays (MWA, LWA) = science and technology precursors • Deep Space Network Array: closely related to US SKA concept, strong possibilities for economies of scale • Explicit SKA development: • NSF ATI Grant: ($1.5M) 2002-2005 • Technology Development Project (TDP) • $32M over 5 years (NSF proposal pending) • End to end development, costing, preliminary design • Organized through the US SKA Consortium (17 institutions) • Managed by NAIC/Cornell • Facilitates and unifies SKA development at NRAO, NAIC, and institutions involved with low-frequency array development Jim Cordes: SKA: Pulsars and Gravity

  16. Siting the SKA • Current siting decision is late 2006 (ISPO) • Argentina, Australia, China, South Africa: proposals expected by end of 2005 • Working plan: single site for all frequencies, covered with 2 to 3 antenna technologies (subject to optimization vs. cost/performance) • Dipoles  ≤ 0.3 GHz • Aperture array 0.3 ≤  ≤ 2 GHz • Paraboloids 1 ≤  ≤ 25 GHz • US perspective: • SKA low-frequency array in southern hemisphere • radio quiet zone •  ≤ 2 GHz • SKA high-frequency array built upon the EVLA+VLBA • Better tropospheric properties than southern sites, RFI less an issue • leverages existing investments • recognizes international utilization of EVLA, VLBA • Proposed by the US SKA Consortium to the International SKA Steering Committee as a Discussion Document (2005 April) Jim Cordes: SKA: Pulsars and Gravity

  17. Issues for SKA Searching and Timing • Collecting area needs a significant fraction in a compact core array to allow wide FOV searches with acceptable data rates (10 yr from now!) • Beam forming + pulsar search analysis in > 104 pixels • ~ 1015 op s-1 (scales with diameter2 of core array) • Need high-frequency capability to search/time pulsars in the star cluster around SgrA* • Interstellar multipath: d ~ 300 s -4 ( in GHz) •  10 to 15 GHz (higher?) c.f. pulsar steep spectra, but some are ~flat • Timing: above a single-pulse S/N ~ few, timing precision is determined by factors other than S/N: • Single pulse amplitude and phase fluctuations • Interstellar scattering effects • Polarization calibration • So many pulsars to time! • need to exploit multiple beaming capability of a large scale, distributed array or time only the best objects All can be mitigated to some extent Jim Cordes: SKA: Pulsars and Gravity

  18. Blind Surveys with SKA • (pulsars, transients, ETI) ≥104 beams needed for full-FOV sampling • Number of pixels needed to cover FOV: Npix~(bmax/D)2 ~104-109 • Number of operations Nops~ petaop/s • Post processing per beam: single-pulse and periodicity analysis Dedisperse (~1024 trial DM values) + FFT + harmonic sum (+ orbital searches + RFI excision) • Correlation is more efficient than direct beam formation • Requires signal transport of individual antennas to correlator Jim Cordes: SKA: Pulsars and Gravity

  19. Sampling the pulsar luminosity function in Sgr A* and other galaxies GC = GC++ Pulsar detectability with the SKA for GC pulsars and extragalactic pulsars High frequencies are needed for searches of the Galactic Center owing to intense radio wave scattering Jim Cordes: SKA: Pulsars and Gravity

  20. Pulsar Astrometry with the SKA • Pulse timing models and reference frame definition • Proper motions and parallaxes for objects across the Galaxy  monitoring programs over ~ 2 yr/pulsar • Optimize steep pulsar spectra against -dependence of ionospheric and tropospheric and interstellar phase perturbations ( 2 to 8 GHz) • In-beam calibrators (available for all fields with SKA) • 10% of A/T on transcontinental baselines implies 20 times greater sensitivity over existing dedicated VLB arrays Jim Cordes: SKA: Pulsars and Gravity

  21. Issues: Spin stability of NS (spin noise) Spin rate Orientation effects (precession) Glitches Stability of the radiation beam “attached’’ to the spinning NS Beam wavering from precession Pulse amplitude and phase jitter (radiation coherence effects) Effects on propagating pulses by the intervening ISM (plasma effects) Time tagging of measured pulses Pulsar Timing Jim Cordes: SKA: Pulsars and Gravity

  22. Mitigation of TOA Estimation Errors • Polarization purity • need -40dB accuracy after hardware and post processing across the entire FOV used for timing • Pulse amplitude/phase jitter •  limitations on optimality of matched filtering • Error-correction algorithms: use correlations of pulse shape perturbation with TOA perturbation (unpublished) • Electron density fluctuations in the ISM • 103 km to > pc (~Kolmogorov) • DM(t) … correctable • Time-variable pulse-broadening function … partly correctable • Secular (months, years): refractive modulation • N effects from finite number of scintles in the f-t plane • Time-variable angle of arrival • Refraction from large-scale structures in the ISM Jim Cordes: SKA: Pulsars and Gravity

  23. Discussion Issues • Pulsar timing precision: how to improve? • Choice of frequency vs. pulsar • State of the art polarization calibration • DM(t), scintillation corrections • Error correction for intrinsic pulse fluctuations • Pulsar array: • Large N of pulsars vs. pulsars of opportunity (small N)? Jim Cordes: SKA: Pulsars and Gravity

  24. Discussion Issues • Design and usage issues for the SKA • Size of core array usable for searching • Polarization calibration across wide FOV • How to deal with the huge number of new pulsars: • Time only the best after initial quick assessment? • Require multibeam capability? Jim Cordes: SKA: Pulsars and Gravity

  25. Discussion Issues • Astrofinance and politics: • Need to jointly promote gravity studies: • Laboratory and spacecraft gravitational wave detectors • Pulsars as clocks and gravitational laboratories • Sometimes perceived as having no connection and/or in competition • Joint SKA and LISA meeting? (Kramer) Jim Cordes: SKA: Pulsars and Gravity

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