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ALFA Pulsar Surveys Jim Cordes, Cornell University GALFA Workshop, Arecibo 20 March 2003

ALFA Pulsar Surveys Jim Cordes, Cornell University GALFA Workshop, Arecibo 20 March 2003. Pulsar Consortium meeting 1-2 Nov 2002 http://alfa.naic.edu/alfa_pulsar.html Preliminary survey descriptions Spectrometer needs Organization of the consortium & working groups Data management

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ALFA Pulsar Surveys Jim Cordes, Cornell University GALFA Workshop, Arecibo 20 March 2003

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  1. ALFA Pulsar SurveysJim Cordes, Cornell UniversityGALFA Workshop, Arecibo 20 March 2003 • Pulsar Consortium meeting 1-2 Nov 2002 http://alfa.naic.edu/alfa_pulsar.html • Preliminary survey descriptions • Spectrometer needs • Organization of the consortium & working groups • Data management • how to serve 1 Pbyte of data? • long-term archiving

  2. Boundary Conditions etc. • ALFA surveys can be viewed as part of a long-term, grander effort (“Full Galactic Census”) (LOFAR, SKA, ) • ALFA surveys usher in a new NAIC mode of operation (not business as usual) • RFI mitigation required and provides general purpose tools • Data & data products = long term resources  data management policy & resources • The scientific pie is large enough for shared glory but … • A focused, concerted, committed effort is needed for (a) the best surveys (b) legacy results • Exploit telescope time fully (transients, piggybacking)

  3. Why more pulsars? • Extreme Pulsars: • P < 1 ms P > 5 sec • Porb < hours B > 1014 • V > 1000 km s-1 • Physics payoff (GR, LIGO, GRBs…) • Population & Stellar Evolution Issues • Use pulsars to probe the ISM (ne, B) • The high-energy connection (e.g. GLAST) • Serendipity (strange stars, transient sources)

  4. Targeted Classes of Pulsars • Young, canonical pulsars (Galactic plane) • Recycled pulsars (MSPs) (out of plane) • High-velocity pulsars • NS-NS and NS-BH binaries • Pulsars ‘beyond the death line’ (radio magnetars?) • Precessing pulsars • Globular cluster MSPs • X-and--ray selected pulsars • Transient sources (e.g. giant pulses)

  5. ALFA Pulsar Surveys • Galactic plane |b| < bmax~ 3 to 5 deg • Intermediate latitudes (bmax |b|  15 to 25 deg) • Deep surveys toward specific objects - high-energy selected targets (multibeam for RFI) - extended targets (clusters, HII complexes, spiral-arm tangents) • Extragalactic targets - giant pulses from M33 (~24 ALFA pointings) • Pulsar/transients survey piggybacked on high b HI survey? (multiple passes) • Other

  6. Dmax vs. Flux Density Threshold Scattering limited  Dispersion limited Luminosity limited PMB (2100 s)

  7. Dmax vs. Flux Density Threshold Scattering limited   Dispersion limited Luminosity limited ALFA (300 s) PMB (2100 s)

  8. Pulse broadening from multipath

  9. Implications: • Optimal integration time:stay close to the luminosity-limited regime • Fast-dump spectrometers:need sufficient number of channels so that search is not DM limited • Better to cover more solid angle than integrating longer on a given direction(as long as all solid angles contain pulsars)

  10. Comparison of AO, GBT & Parkes (Smin1 held fixed) *Ssys = 3.6 Jy for Pix > 0 2.8 Jy for Pix=0 ~ 2.3 Jy for new LBW

  11. Comparison of AO, GBT & ParkesSmin1 (AO) << Smin1 (Parkes) Ssys Dn Nch T Smin1 dt/d (Jy) (MHz) (s) (Jy) (hr/deg2) AO 3.6 300 1024 300 85 29/Nb=4.2 GBT 16 400 1024 900 190 4.5/Nb Parkes 36 288 96 2100 360 1 (Nb=13)

  12. Nominal Parameters of Galactic Plane Survey • 300 MHz bandwidth • 1024 channels • 64 s dump time • polarizations summed • ~4 bits/sample • 7 beams • 300 s dwell time • 400 TB in 2000 hr 30< l < 80 deg |b| < 5 deg  56 (Nbits/4) MB/s 3 yr @ 50%

  13. Surveys with Parkes, Arecibo & GBT. Simulated & actual Yield ~ 1000 pulsars.

  14. Spectrometer Requirements • Input to spectrometer (FPGA based): • 7 beams x 2 polarizations x 300 MHz •  8 bit samples • Output to disk: • 1024 spectral channels ( 0.3 MHz) • Spectral normalization (S / S - 1) • Polarizations summed • Selectable output bits (2, 4, 8 …) • 64 s dump times • Desirable features: • Selectable polyphase filter shapes • Selectable number of channels • Subbanding (~100 MHz, variable overlap) • Selectable dumptimes (e.g. 4-256 s)

  15. II. Intermediate Latitude Survey Search for: • Millisecond pulsars (z scale height ~ 0.5 kpc) • High-velocity pulsars (50% escape) (scale height = ) • NS-NS binaries (typical z ~ 5 kpc) • NS-BH binaries (typical z ~ few kpc ?) ~ 1500 hours (~60 sec, piggyback, filler time?)

  16. Search processing  High Performance Computing + well-organized data management t: 107 : 103 >2004: a cluster of Beowulf clusters can keep up with real time at observing duty cycle 2002: single processor  200 x real time

  17. Data Management • Raw data • Local processing (inc. quicklook) • Processing at Consortium member institutions • Short and long-term archiving (disk/tape) • Central mainland location with high-bw pipe? • Database catalog system • Web based data selection • Intermediate Data products • candidate lists • RFI identification • diagnostic plots • Final products (catalogs, pulse profiles, timing models) Implied Linkage to the National Virtual Observatory as appropriate

  18. What Next? • New survey simulations • Population issues (PMB), NE2001 • Optimize number of detections vs l,b,T,scintillations, etc • Design at-the-telescope survey modes • Beam interlace, hour angles, feed rotation • RFI studies, pilot observations, simulations • Search code development (~TEMPO, not AIPS++) • Data management plan • Plan survey follow-up (timing, multi-)

  19. Issues for Optimizing Surveys • RFI management • Characterization, test obs & algorithms, multibeam schemes (ALFA + other?) • Diffractive ISS •  multiple passes favored for low DM • -t weighting for intermediate DM • no action for high DM • Refractive ISS •  multiple passes for low to intermediate DM • Nulling  multiple passes • “Search” vs. “confirmation” • Historically two different phases • PMB: candidate density  Tconfirm ~Tsearch  do two “searches” = two passes on sky

  20. Pulsar Consortium Working Groups • Surveys (J. Cordes) • Data acquisition (I. Stairs) • Post processing (D. Lorimer) • Data Management (S. Ransom) • Follow-up observations (B. Gaensler)

  21. Preliminary Protocols • Consortium membership: • open policy early on, by application later • protection of student projects • Data access: • open to all members during proprietary period • by application from nonmembers (during proprietary period) • uniform, baseline processing for legacy goal • encourage innovative new approaches • Authorship: • rotating lead, equitable • all consortium members • opt out by inactive members (honor system) • Follow up observations:similar to Authorship • Discovery of exotica:full consortium involvement

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