23 June 2005Jim Cordes: SKA: Pulsars and Gravity 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 The Pulsar Key Science Project Massive census of the Galaxy, globular clusters and nearby galaxies Generalized search algorithms Issues for precision timing  20  50

23 June 2005Jim Cordes: SKA: Pulsars and Gravity 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 km 2 ) 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 10 6 meter 2  ~ €1,000 per meter 2 c.f. existing arrays ~ €10,000 per meter 2 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  20  50

23 June 2005Jim Cordes: SKA: Pulsars and Gravity Science with the Square Kilometer Array edited by Chris Carilli Steve Rawlings Special issue of New Astronomy Reviews Volume 48, December 2004, (48 chapters) Five key science projects Discovery science Enabling understanding in fundamental physics and origins

23 June 2005Jim Cordes: SKA: Pulsars and Gravity Five Key Science Areas for the SKA TopicGoals Probing the Dark Ages 1. Map out structure formation using HI from the era of reionization (6 < z < 13) 2. Probe early star formation using high-z CO 3. Detect the first active galactic nuclei Gravity: Pulsars & Black Holes 1. Precision timing of pulsars to test theories of gravity approaching the strong-field limit (NS-NS, NS-BH binaries, incl Sgr A*) 2. Millisecond pulsar timing array for detecting long-wavelength gravitational waves Cosmic Structure 1. Understand dark energy [e.g. eqn. of state; W(z)] 2. Understand structure formation and galaxy evolution 3. Map and understand dark matter Cosmic Magnetism Determine the structure and origins of cosmic magnetic fields (in galaxies and in the intergalactic medium) vs. redshift z The Cradle of Life 1. Understand the formation of Earth-like planets 2. Understand the chemistry of organic molecules and their roles in planet formation and generation of life 3. Detect signals from ET

23 June 2005Jim Cordes: SKA: Pulsars and Gravity

23 June 2005Jim Cordes: SKA: Pulsars and Gravity Other References “Strong-field tests of gravity using pulsars and black holes,” Kramer et al “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 and on arXiv/astro-phwww.skatelescope.org

23 June 2005Jim Cordes: SKA: Pulsars and Gravity Surveys: past, present and future

23 June 2005Jim Cordes: SKA: Pulsars and Gravity 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) Blue points: SKA simulation Black points: known pulsars Millisecond Pulsars Relativistic Binaries Today Future SKA SKA only 6! ~10 4 pulsar detections

23 June 2005Jim Cordes: SKA: Pulsars and Gravity ,, t, pol , ,  t Large processing FOV High sensitivity : 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

23 June 2005 Jim Cordes: SKA: Pulsars and Gravity Pulsar Periodicity Search time Frequency time DM |FFT(f)| FFT each DM’s time series 1/P2/P3/P   

23 June 2005Jim Cordes: SKA: Pulsars and Gravity The power of ALFA: I(, t,  j ) j=1,7

23 June 2005Jim Cordes: SKA: Pulsars and Gravity ALFA pulsar surveys will be the deepest surveys of the Galaxy until the SKA is built: Blue: known pulsars (prior to Parkes MB) Red: Parkes MB Green: PALFA simulated pulsars

23 June 2005Jim Cordes: SKA: Pulsars and Gravity 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

23 June 2005Jim Cordes: SKA: Pulsars and Gravity Comparison of maximum detectable distance vs. P and pulsar luminosity

23 June 2005Jim Cordes: SKA: Pulsars and Gravity

23 June 2005Jim Cordes: SKA: Pulsars and Gravity 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) 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

23 June 2005Jim Cordes: SKA: Pulsars and Gravity 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 array0.3 ≤ ≤ 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)

23 June 2005Jim Cordes: SKA: Pulsars and Gravity Notional Time Line

23 June 2005Jim Cordes: SKA: Pulsars and Gravity 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 > 10 4 pixels ~ op s -1 (scales with diameter 2 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

23 June 2005Jim Cordes: SKA: Pulsars and Gravity Blind Surveys with SKA Number of pixels needed to cover FOV: N pix ~(b max /D) 2 ~ Number of operations N ops ~ 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 (pulsars, transients, ETI) ≥10 4 beams needed for full-FOV sampling

23 June 2005Jim Cordes: SKA: Pulsars and Gravity Sampling the pulsar luminosity function in Sgr A* and other galaxies 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 GC = GC++

23 June 2005Jim Cordes: SKA: Pulsars and Gravity 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

23 June 2005Jim Cordes: SKA: Pulsars and Gravity Pulsar Timing 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

23 June 2005Jim Cordes: SKA: Pulsars and Gravity Times of Arrival (TOAs) Issues in time tagging: Accurate pulse shape Minimize distortions from instrumental polarization, etc. Minimize distortions from interstellar propagation Large signal-to-noise ratio Number of pulses in summed pulse shape Matched filtering of template pulse shape

23 June 2005Jim Cordes: SKA: Pulsars and Gravity Pulse Timing Can never have too much timing precision!  TOA << 100 ns is desirable TOA fluctuations: Radiometer noise:  TOA  W  SEFD (P/T) 1/2 Pulse phase jitter:  TOA  f j W(P/T) 1/2 Scattering-induced errors: DM variations, variable pulse broadening:  TOA (DM)  -2,  TOA (PB)  -4 Pulse polarization + calibration errors  pulse shape changes  TOA errors –Need Stokes total I precision  1% or voltage polarization purity to better than (-40 dB)

23 June 2005Jim Cordes: SKA: Pulsars and Gravity 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 10 3 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

23 June 2005Jim Cordes: SKA: Pulsars and Gravity Pulse Timing Multiple beaming and multiple FOV: –Follow up timing required to varying degrees on the ~ 1-2x10 4 pulsars discoverable with SKA Spin parameters, DM and initial astrometry Orbital evolution for relativistic binaries Gravitational wave detection using MSPs –Each deg 2 will contain only a few pulsars  efficient timing requires large solid-angle coverage (lower frequencies, subarrays, wide intrinsic FOV, or multiple FOVs)

23 June 2005Jim Cordes: SKA: Pulsars and Gravity 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)?

23 June 2005Jim Cordes: SKA: Pulsars and Gravity 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?

23 June 2005Jim Cordes: SKA: Pulsars and Gravity 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)

23 June 2005Jim Cordes: SKA: Pulsars and Gravity B l,b = 91.3 o, 52.3 o D = kpc V  = km s -1 P = 0.74 s B = 2x10 12 G  s = P/2Pdot = 2.36 Myr The highest measured velocity using direct distance measurement 2.5x further than electron density model based distance estimate (NE2001) Chatterjee et al. submitted Possibly born in Cyg OB 7

23 June 2005Jim Cordes: SKA: Pulsars and Gravity Progress towards AANM Initiatives Prior Decade ALMA: under construction Major Initiatives EVLA: Phase I underway; Phase II under review Moderate Initiatives SKA: Multithreaded technology development in the US and around the world. CARMA: under construction FASR: proposal for D&D about to be submitted SPT: under construction Small Initiatives Low-f arrays: : Several initiatives underway/pending CMB experiments Numerous, on-going New Ground Based Initiatives

23 June 2005Jim Cordes: SKA: Pulsars and Gravity Questions that the SKA can address Fundamental Physics What is dark matter? What is dark energy? Did Einstein have the last word on Gravity? How do cosmic accelerators work and what are they accelerating? What are the new states of matter at exceedingly high density and temperature? Is a new theory of light and matter needed at the highest energies? Complexity in the Universe How does a ‘simple’ big bang turn into a universe with stars, planets and life? How do planetary systems form? How common are planetary systems? What is the role of interstellar molecules in jump starting life on planets? Is intelligent technological life common or rare?

23 June 2005Jim Cordes: SKA: Pulsars and Gravity The Collecting Area Plateau in Radio Astronomy Recent growth in sensitivity has exploited low-noise devices, developments in digital signal processing bandwidth, and calibration and imaging techniques. Increased collecting area enables: Detection of L* galaxies in HI at z ~2 Epoch of Reionization analysis GRB afterglows  100 fainter than currently Detection/timing of pulsars near Sgr A* Gap structure in young, protoplanetary disks

23 June 2005Jim Cordes: SKA: Pulsars and Gravity SKA Frequencies and Technologies

23 June 2005Jim Cordes: SKA: Pulsars and Gravity The International SKA Project International SKA Project Office (ISPO) Richard Schilizzi (Director) Peter Hall (Project Engineer) Project Scientist (TBD) Is conducting site testing in advance of site selection International SKA Steering Committee (ISSC) 21 total members 7 US members (reflects anticipated funding level) Working groups: Science, Simulations, Site Evaluation, Engineering, Operations, Outreach Advisory Committees (Science, Site Selection, …) 1/3 representation

23 June 2005Jim Cordes: SKA: Pulsars and Gravity SKA Challenges Technology Project Management Wideband, efficient antennas Fast, long-distance, data transport High performance DSP & computing hardware New data processing and visualization techniques Evolving science goals High levels of technical risk International politics –Funding mechanisms Ambitious delivery timescale Industry liaison –Pre-competitive alliances + procurement + project delivery Performance + Cost

23 June 2005Jim Cordes: SKA: Pulsars and Gravity Roles of Arecibo and the GBT on the Path to the SKA Arecibo: low frequencies, high sensitivity, radar capability Surveys with ALFA: galactic and extragalactic Transient and pulsar surveys, timing: tests of GR largest pulsar survey until SKA surveys commence High Sensitivity Array (HSA) for VLBI: time domain, mJy VLBI Solar System radar: NEOs, planetary surfaces, rings SKA testbed: wide bandwidth (2-11 GHz) focal plane array Partnerships for surveys, instrumentation and software Data management of large-scale surveys (PALFA ~ 1 Petabyte) GBT: Roles for EVLA, ALMA and SKA Beam-forming array: Galactic HI Penn Array: pathfinder for SZ, dust Heterodyne array: CO, HCN, HCO+ in star forming regions Multibeam at 30 GHz: blind high-z CO (Finding surveys for EVLA, ALMA) Targeted pulsar surveys (globular clusters) and shallow blind surveys High frequency VLBI: H 2 0 masers Bi-static radar: NEO’s, Titan

23 June 2005Jim Cordes: SKA: Pulsars and Gravity Low Frequency Arrays The low frequency regime (< 300 MHz) largely unexplored Exciting Science: “Dark Ages”: neutral hydrogen First supermassive blackholes Continuum transients Solar/ionospheric phenomena Dutch pursuing low frequency array (LOFAR) on European site Several US projects now in preliminary stages (see URLs at end) Primeval Structure Telescope (prototyping stage, proposal under review) Mileura Widefield Array (prototyping, proposal under review) Long Wavelength Array (prototyping and funding now being sought) Modest investment in next 3-5 years : Detection of neutral hydrogen during the “Dark Ages” Low-f transient sky (GRBs? Cosmic ray events. Blind Surveys) Science and technology pathfinder towards the low-frequency portion of the SKA

23 June 2005Jim Cordes: SKA: Pulsars and Gravity RMS Roadmap to the SKA: The EVLA+VLBA Complete and support EVLA Pursue aggressively the SKA concept as the next generation radio telescope The high-frequency SKA can build upon the EVLA and VLBA, as is now being promoted by the US SKA Consortium to the international SKA community

23 June 2005Jim Cordes: SKA: Pulsars and Gravity RMS Roadmap Technology Development Area Source/Venue Antenna ManufactureCommercial, DSNA, SKA-TDP Data transportEVLA, eVLBI, SKA(Int) Broadband feeds/rcvrsATA, AO, GBT, SKA-TDP Correlator designEVLA, ATA, LOFAR, SKA(Int) Algorithms: Time domain Spectral domain Imaging domain ATA, EVLA, ALMA, LOFAR, MWA, LWA, SKA-TDP Matched filtering, wide FOV Wide field, high resolution Wide field, high res, high dynamic range Data ManagementAO/ALFA, ATA, EVLA, ALMA, SKA-TDP Large-N/Small D conceptATA, DSNA Operations research of large N arrays University OR, commercial, SKA-TDP Towards the SKA: Technology Pathway

23 June 2005Jim Cordes: SKA: Pulsars and Gravity RMS Roadmap Science AreaInstrument Epoch of ReionizationPaST, MWA, LWA, LOFAR Gravity, pulsarsAO/ALFA, GBT, ATA, SKA-demos First AGNsEVLA/VLBA+OIR cross catalog, LWA, SKA- demos Protoplanetary disksEVLA, GBT Cosmic magnetismEVLA, VLBA+GLAST,ATA, GBT, LWA, SKA- demos Transient universeAO/ALFA, GBT, EVLA, MWA, LWA, ATA, LOFAR Galaxy evolution, e.g. HI mass distribution Weak lensing Dark energy EOS EVLA, VLBA, GBT, AO/ALFA, ATA, MWA, LWA, SKA demos Towards the SKA: Science Pathway Plus connections to ALMA, JWST, GSMT, GLAST, etc

23 June 2005Jim Cordes: SKA: Pulsars and Gravity The Radio Astronomy Plan (cm/m) The US can build upon its highly successful investment in RA for its participation in the SKA, a telescope too large to be built by any one country. Science and technology development and demonstrators should make use of the existing portfolio of facilities, where appropriate, combined with new investment in pathfinder arrays and technology development. The metric for success is the scientific discovery and understanding that can be expected in a “go as you grow” mode from now through SKA operations. Fundamental physics (gravity, cosmology, dark energy) Fundamental astrophysics (magnetism, structure formation, first black holes) Astrobiology (organic molecules, planet formation, SETI) Radio facilities will be used synergistically with those across the entire EM spectrum + non-EM (gravitational waves, neutrinos, cosmic rays) in forefront science areas, both now and with the SKA. Radio astronomy will help define the forefront Phase out of existing facilities or near-term pathfinders is expected but would be a strong function of SKA capabilities and time frame

23 June 2005Jim Cordes: SKA: Pulsars and Gravity URLs for cm/m Radio Astronomy ATA (Allen Telescope Array) Arecibo/NAIChttp:// DSN Arrayhttp://dsnarray.jpl.nasa.govhttp://dsnarray.jpl.nasa.gov EVLAhttp:// GBThttp:// LWA (Long Wavelength Array) MWA (Mileura Widefield Array) PaST (Primeval Structure Tel) SKA (International) (US SKA Consortium) VLBAhttp://

23 June 2005Jim Cordes: SKA: Pulsars and Gravity Primary beam & synthesized beams Blind surveys require full FOV sampling

23 June 2005Jim Cordes: SKA: Pulsars and Gravity Arecibo + SKA Surveys