Transcript PPT

ALFA Pulsar Surveys
Jim Cordes, Cornell University
Arecibo 16 March 2003
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Pulsar Consortium meeting 1-2 Nov 2002
Preliminary survey plans
Hardware needs
Organization of the consortium & working groups
Synergies with other science goals (EALFA, GALFA)
Data management (how to serve 1 Pbyte of data?,
long-term archiving)
Targeted Classes of Pulsars
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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)
Why more pulsars?
• Extreme Pulsars:
• P < 1 ms
P > 5 sec
• Porb < hours
B > 1014 G
• V > 1000 km s-1
• Population & Stellar Evolution Issues
• Using pulsars to probe the ISM (gas & magnetic field)
• The high-energy connection (e.g. GLAST)
• Physics payoff (GR, LIGO, GRBs…)
• Serendipity (strange stars, transient sources)
Search processing  High Performance Computing +
well-organized data management
t: 107 : 103
2002: single processor
 200 x real time
>2004: a cluster of
Beowulf clusters can
keep up with real time
at observing duty cycle
Pulse broadening from multipath
Dmax vs. Flux Density Threshold
Scattering
limited
Dispersion
limited
ALFA
Luminosity
limited
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)
ALFA Pulsar Surveys
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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)
IV. Extragalactic targets
- giant pulses from M33 (~24 ALFA pointings)
V.
Piggyback pulsar/transients survey on high b
HI survey? (multiple passes)
VI. Other
Nominal Parameters of Galactic
Plane Survey
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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 MB/s
3 yr @ 50%
Comparison of AO, GBT & Parkes
(Smin1 held fixed)
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Site
GHz
Ssys

Nch
t
s
Tint
s
hr/deg2
330
3.6
2.0/Nb
330
9
4.7/Nb
2100 330
14
13.6/Nb
MHz
3.6*
300
1024
64
20
GBT 1.4
16
400
1024
64
300
PMB 1.4
36
288
*S
1.4
sys =
3.6 Jy for Pix > 0
96 250
Jy
FWHM dT/d
arcmin
Jy
AO
Smin1
2.8Jy for Pix=0
~ 2.3 Jy for new LBW
Comparison of AO, GBT & Parkes
Smin1 (AO) << Smin1 (Parkes)
Ssys

(Jy)
(MHz)
Nch
T Smin1
dt/d
(s)
(Jy)
(hr/deg2)
85
AO
3.6
300 1024
300
GBT
16
400 1024
900 190
Parkes
36
288
96
2100 360
29/Nb=4.2
4.5/Nb
1 (Nb=13)
Surveys
with Parkes,
Arecibo &
GBT.
Simulated &
actual
Yield ~ 1000
pulsars.
Spectrometer Requirements
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300 MHz bandwidth (full feed)
<0.3 MHz channels
FPGA Correlator or
FPGA-FFT or Polyphase filter approach
Fast dump capability
Polarization summing mode
Needs rapid decision (this month)
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 (piggyback, filler time?)
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
What Next?
• New survey simulations
• Population issues (PMB), NE2001
• Optimize number of detections vs l,b,t,etc
• Design at-the-telescope survey modes
• Beam interlace, hour angles, feed rotation
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RFI studies, pilot observations, simulations
Search code development (~TEMPO, not AIPS++)
Data management plan
Plan survey follow-up (timing, multi-)
Pulsar Consortium Working Groups
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Surveys
Data acquisition
Post processing
Data Management
Follow-up observations
(J. Cordes)
(I. Stairs)
(D. Lorimer)
(S. Ransom)
(B. Gaensler)
Preliminary Protocols
• Consortium membership:
– open policy early on, by application later
– protection of student projects
• Data access:
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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
Data Management
• Raw data
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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
Implied Linkage
Web based data selection
to the National
Intermediate Data products
Virtual
– candidate lists
Observatory as
– RFI identification
appropriate
– diagnostic plots
• Final products (catalogs, pulse profiles, timing
models)
Pilot Database Storage
(Cornell Theory Center)
Database information:
• Microsoft SQL Server
• Hosted at the Cornell Theory Center
• Stores both raw data and heavily processed data
• For the raw data simple queries will select chunks
to serve out for users
• The processed data can be searched and analyzed
with complex queries
• Database will be tuned to perform better for
common/expected queries
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)