Pulsars and Transients: ALFA and Beyond Jim Cordes Cornell University • Arecibo and ALFA surveys • Galactic plane pulsar and transient survey • PALFA Consortium • Prospects • Context within the era of SKA pathfinders • Campaigning for Arecibo 17 August 2007 Pulsars 40th Montreal 1 17 August 2007 Pulsars 40th Montreal 2 17 August 2007 Pulsars 40th Montreal 3 Focal Plane 17 August 2007 Pulsars 40th Montreal 4 ALFA Science Goals: Massive Surveys • Extragalactic atomic hydrogen (H I) surveys: • • • • • • • Interstellar turbulence Disk-halo connection (chimneys & fountains) Galactic structure and dynamics Continuum surveys • Galactic synchrotron radiation (magnetoionic medium) Pulsar science: • • (G-ALFA) Low-and-high-latitude H I surveys • • Zone of avoidance galaxies All (Arecibo) sky search for low-mass H I clouds and galaxies High-velocity clouds Galactic science: • (E-ALFA) (P-ALFA) Deep surveys + follow up pulse timing studies SETI: to be done simultaneously with pulsar surveys http://alfa.naic.edu/ (specifications, memos, consortia) 17 August 2007 Pulsars 40th Montreal 5 PALFA Survey Goals Arecibo can provide the most sensitive high-frequency surveys until the SKA (but c.f. sky coverage) 500 - 103 pulsars – – – – – – Galactic plane survey: |b|<5, 32 < l < 77, ~300s dwell times Intermediate latitude survey: 5 < |b| < 15 for MSPs, NS-NS 64 s, 256 channels across 100 MHz with current spectrometers Reach edge of Galactic population for much of luminosity function High sensitivity to millisecond pulsars (smearing 120 s for DM = 100) Dmax = 2 to 3 times greater than for Parkes MB Sensitivity to transient sources (algorithms) Data management – – – – Keep all raw data ~ 1 Petabyte after 5 years at the Cornell Theory Center Database of raw data, data products, end products Virtual observatory linkage eventually 17 August 2007 Pulsars 40th Montreal 6 PALFA Survey Goals Pulsars and Gravity: – Relativistic binaries (NS-WD, NS-NS, NS-BH): as laboratories for testing GR in the strong-gravity limit » J1906+0746 (second born NS in NS-NS system) 144 ms, 3.98 hr orbit » Paper in preparation (Kasian et al.) – Pulsar timing array objects: millisecond pulsars with low “timing noise” that allow detection or strong limits on nHz gravitationalwave backgrounds » J1903+03, 2.15 ms (Champion et al.) High-energy/radio-pulsar synergies: » J1928+1746 (68 ms pulsar in EGRET error box) Intermittent pulsars (RRAT like) » J0628+09 + 7 others Galaxy/Interstellar Medium: – Large number of pulsars allows modeling of electron density and magnetic field (DM, SM, RM + multi- obs) 17 August 2007 Pulsars 40th Montreal 7 First Results 11 new pulsars: 1 binary, 1 w/ possible gamma-ray counterpart, 1 transient source Exploited database of Parkes Multibeam survey + multiobservatory followup 17 August 2007 Pulsars 40th Montreal 8 The FIRST PALFA Millisecond Pulsar: J1903+03 (Champion et al. in preparation) P = 2.15 ms DM = 297 pc cm-3 (highest for any MSP) S/N = 24.2 Binary parameters: Porb = 95 days e = 0.44 Found in McGill search pipeline Confirmed in Cornell pipeline with same S/N 17 August 2007 Pulsars 40th Montreal 9 J1903+03 = distant MSP • Total mass = 2.5 Msun • Minimum companion mass = 1.0 Msun • e = 0.44 • High DM pulsar in the Galactic plane: • narrow channels in survey spectrometers • number of implied MSPs depends on origin (from GC or from disk?) 17 August 2007 Pulsars 40th Montreal 10 PALFA Survey Pipeline Main steps: • Recording and quicklook analysis • Shipping data from AO to CTC • Full resolution processing at Cornell and other sites • Consolidation of processing results into db • Filtering candidates for reobservation http://arecibo.tc.cornell.edu/PALFA PALFA Databases at Cornell Center for Advanced Computing 17 August 2007 Pulsars 40th Montreal 12 PALFA Status • • • • • Galactic plane survey requires 48k pointings To date: 14k pointings 120 known pulsars “rediscovered” 36 confirmed discoveries ~ 100 candidates to reobserve 2007 Fall • Arecibo downtime summer 2007 for painting 17 August 2007 Pulsars 40th Montreal 13 Signal Signatures • Classic: sharp pulses, steady amplitudes • Realism: expect low duty cycle pulsars • Nearly aligned rotators • Highly scattered pulsars (large DM, distant) • Orbitally broadened (mitigated by acceleration search) • Neo: • highly intermittent objects (e.g. “RRATs”) • other source classes: – Pulsars: TOE simultaneous, TOA differential (dispersion) – Other transients: TOE simultaneous, TOA differential • Realism II: RFI 17 August 2007 Pulsars 40th Montreal 14 DM Frequency Pulsar Periodicity Search time time FFT each DM’s time series |FFT(f)| 1/P 17 August 2007 Pulsars 40th Montreal 2/P 3/P 15 Single pulse searches 17 August 2007 Pulsars 40th Montreal 16 Two pulsars in one beam 17 August 2007 Pulsars 40th Montreal 17 17 August 2007 Pulsars 40th Montreal 18 17 August 2007 Pulsars 40th Montreal 19 17 August 2007 Pulsars 40th Montreal 20 17 August 2007 Pulsars 40th Montreal 21 17 August 2007 Pulsars 40th Montreal 22 17 August 2007 Pulsars 40th Montreal 23 17 August 2007 Pulsars 40th Montreal 25 17 August 2007 Pulsars 40th Montreal 26 Signal detection through stacked multiple single pulses (dedispersed) Stacked signal in the frequency-time plane (dispersion signature) 17 August 2007 Pulsars 40th Montreal 27 Single-pulse vs. Periodicity Detection Have pulsars been missed? r = (S/N)SP / (S/N)FFT Higher S/N from SP detection r>1 implies SP detection more efficacious Depends on number of periods Np in the data set Higher S/N from FFT analysis SP detection tends to be superior for small Np Implication for future telescopes (e.g. SKA) Julia Deneva, work in progress 17 August 2007 Pulsars 40th Montreal 28 Near and Longer Term • Observations will re-commence ~ 1 Oct ’07 • New spectrometers available this Fall • 300 MHz total bandwidth vs. 100 MHz of WAPPs • polyphase filter banks vs. correlators » May be less affected by RFI • Timing follow up at Arecibo, GBT (Nice, Stairs, Lorimer et al.) • Can expect GP survey and mid-latitude surveys to continue for many years • Transient surveys can run simultaneously with the all-SKY ALFALFA (HI) survey, along with SETI, etc. 17 August 2007 Pulsars 40th Montreal 29 MeerKAT Timeline 10% SKA Phase I ATA LOFAR MWA/LFD MIRA ASKAP Full SKA LWA Now 2008 2009 2014 2020 ATA Size LOFAR MeerKAT MIRA 100-m class Full SKA SKA Phase I Arecibo class SKA A community meeting to promote Arecibo science over the next 5 -15 years The NSF is seeking new business models for its facilities Need to reconvince ourselves and the community of Arecibo’s importance 17 August 2007 Pulsars 40th Montreal 32 Extra Slides 17 August 2007 Pulsars 40th Montreal 33 Dmax vs P Dmax = maximum detectable distance for period P given luminosity Lp Detection curves take into account interstellar scattering (NE2001 model) instrumental effects, additive noise 17 August 2007 Pulsars 40th Montreal 34 A pulsar found through its singlepulse 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 17 August 2007 Pulsars 40th Montreal 35 Matched filtering in the t-RF plane Allow more signal classes than is typical c.f. cluster analysis in LIGO t-f plane for unmodeled bursts Post-detection dedispersion: sum intensity along dispersion path Coherent dedispersion: unwrap phases 17 August 2007 Pulsars 40th Montreal 36 17 August 2007 Pulsars 40th Montreal 40 Figure of Merit for Radio Survey Capabilities 17 August 2007 Pulsars 40th Montreal 41 For 1.4 GHz 17 August 2007 Pulsars 40th Montreal 42 Blind Surveys with SKA • Number of pixels needed to cover FOV: • Npix~(bmax/D)2 ~104 • Number of operations to form beams • Nops~ petaop/s ≥104 beams needed for full-FOV sampling • Post processing per beam: • • • • • Single-pulse and periodicity analysis Dedisperse (~1024 trial DM values) FFT + harmonic sum Orbital searches (acceleration ++) RFI excision • Correlation is more efficient than direct beam formation • Requires signal transport of individual antennas to correlator • Post processing ~ 10% of beam forming 17 August 2007 Pulsars 40th Montreal 43 SKA Program Plan A personal take on what should be proposed to the Decadal Survey • EoR Array: < 0.3 GHz – Science goal: detection and imaging of EoR – Array optimized for this goal, separable from (the rest of) the SKA – Context: Informed by LOFAR, MWA, PAPER (detection!) – Expand later as imaging array contingent on results from current arrays – Substantial U.S. contribution next decade • Radio Synoptic Survey Telescope: 0.3 – 3 GHz (higher desireable) – Survey oriented: Dark Energy, Gravity/Pulsars, Transients, Magnetism, Relativistic objects – Consistent with Reference Design but needs technology decisions and optimization – U.S. a significant partner with specific deliverables consistent with funding and time line (E.g., antenna/feed designs, processing algorithms, backends) • High-frequency Array: 1–25 GHz – Science goals: Imaging protoplanetary disks, high-z CO, SETI; – Follow-on to EVLA, ALMA; complementary to JWST, TPF, etc. – Consistent with Reference Design – Siting re-evaluated based on characteristics of RSST array site – Substantial U.S. contribution – Deferred construction 17 August 2007 Pulsars 40th Montreal 44 Summary • Target classes for transients • • • • Relativistic objects (stellar, AGN) Planets, brown dwarfs ETI other? • Keys to discovery at radio wavelengths • Time-frequency (t-) • Wide-field sampling () • Low-mid-high sensitivity (smin) • Blind surveys of the radio sky • Expand AeT • Comprehensive matched filtering (computing) • Start now (Arecibo, GBT, Parkes ATA,LWA,MWASKA1SKA • The SKA Program: • RSST for parallel key science • Cross correlations with other synoptic surveys (EM, CR, GW) 17 August 2007 Pulsars 40th Montreal 45 SKA Science Before the SKA • Pulsars: • • • • Strive for full Galactic census (including GCs and GC) Pulsar timing array: Roadmap from now to the SKA Techniques for improving timing precision Faraday RMs • Transients • Monitor the sky as much as possible with flexible analysis of the time-frequency plane • Solid angle + t-f analysis more important at this stage than sensitivity • Explore cross- synergies 17 August 2007 Pulsars 40th Montreal 47 Asteroids around Pulsars: Relevance to SKA Asteroid belts can produce significant timing noise in MSPs from orbital recoil, influencing the convergence of relativity tests, mass determinations, etc. Long-P pulsars: accreted asteroids will produce a random walk in spin phase from torque pulses Direct detection of tenuous disks is difficult with current telescopes but may be likely with the SKA: 17 August 2007 Pulsars 40th Montreal 48 Initial Ideas About Radio Pulsations • • • • LGMs 1, 2, 3 and 4 White dwarf oscillations Orbital motion of white dwarfs Neutron star spins • Electromagnetic radiation at the spin frequency • Lighthouse model (spinning beam): T. Gold • Similar richness of interpretations for Gamma-ray bursts up to 1990s 17 August 2007 Pulsars 40th Montreal 50 Pulsars and Transients: ALFA and Beyond Jim Cordes Cornell University • • ALFA and consortium science Ongoing pulsar and transient survey • Survey goals • Discoveries so far » PDM » SP • RFI » Examples, summary of variability etc. • Data Management » End to end pipeline » Now » Future • Prospects • Current PALFA survey » New spectrometer » Data delivery by network • • • • 17 August 2007 Out of plane surveys PTA linkage Generalized analyses SKA context Pulsars 40th Montreal 52 Ending Points • The SKA is an ambitious, revolutionary project for tackling fundamental questions in physics, astrophysics and astrobiology • The SKA is likely to be built in three bands with phased construction over the next 15 years • SKA-low • SKA-mid • SKA-high <100 MHz to 300 MHz 0.3 to 3 GHz (or higher) 1 to 25 GHz (or higher) extend EVLA? • SKA-mid can operate as a Radio Synoptic Survey Telescope that does a billion-galaxy survey while also doing gravity/pulsars, magnetic fields and transient science • Building the SKA is a challenge in technology development, in funding and in international politics • Initial arrays will begin construction this decade. • Action: develop science roadmaps that link current facilities with SKA pathfinders and the SKA itself 17 August 2007 Pulsars 40th Montreal 54