joint ligo-virgo data analysis inspiral and burst summary of the first project results overview of...
DESCRIPTION
Coincidence search – simulated data set Noise: 24 hours of Virgo, Hanford and Livingston noise at nominal sensitivities Signals: –Inspiral: [1-3] M from 2 Galaxies NGC 6744 at 10 Mpc M87 at 16 Mpc (Virgo cluster) Random polarization & orbital plane inclination 2PN chirp inspiral generation –Burst: Galactic center direction 2 core collapse simulated waveforms 2 Gaussian peaks 2 CosineGaussians Random polarization Normalization: only one event seen at SNR > 10 In the 3 ITFs over 24 hours.TRANSCRIPT
Joint LIGO-Virgo data analysisInspiral and Burst
Summary of the first project results
Overview of the future activities
M.-A. Bizouard (LAL-Orsay)
on behalf of the LSC-Virgo working group
Hanford Livingston Virgo
Goals - introduction• Benefits of using multiple detectors
– Decrease false alarm– Increase sky coverage – Source location reconstruction with at least 3 detectors– Confirm or eventually kill a “golden” candidate
• Before real data joint analysis: many issues– Different search pipelines comparison– Different sampling rate and sensitivities– What are the expected benefits and performance of the network?– How well can we estimate signal parameters/source location
• Goal of the working group:– Address all the potential issues– Coincidence and coherent analysis– Define a strategy for a burst/inspiral discovery?
SIMULATED DATA!
Project Ia
Project Ib
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Coincidence search – simulated data set
• Noise: 24 hours of Virgo, Hanford and Livingston noise at nominal sensitivities
• Signals:– Inspiral: [1-3] M from 2 Galaxies
• NGC 6744 at 10 Mpc• M87 at 16 Mpc (Virgo cluster)Random polarization & orbital plane inclination2PN chirp inspiral generation
– Burst: Galactic center direction• 2 core collapse simulated waveforms• 2 Gaussian peaks• 2 CosineGaussiansRandom polarizationNormalization: only one event seen at SNR > 10In the 3 ITFs over 24 hours
.
Inspiral search
• Pipelines– Virgo: MultiBandTemplateAnalysis (MBTA) & flat search (Merlino)– LIGO: flat search
• Cross-check that all pipelines are working well and have similar performance running on Virgo and LIGO data.
• Solve few signal generation discrepancies: – G value must be the same– Chirps length must be computed in the same way at 2PN– inspiral end frequency definition: LSO or ISCO
Inspiral coincidence analysis resultsHanford-Livingston-Virgo network performance
• Single interferometer results:– SNR threshold at 6– False alarm rate 0.1 Hz
• Coincidence:– Require time and mass
coincidence
– Triple coincidence• False alarm in 24 hours: 0
– Double coincidence:• False alarm in 24 hours: 1• Adding Virgo gives ~25%
increase in efficiency for M87
H L V HLV
61% 62% 56% 75%
HL HV LV HLHVLV
42% 32% 30% 56%
MBTA efficiencies
M87(16 Mpc)
NGC 6744(10 Mpc)
HLV 24% 48%
quite high source locationoften possible!
M87
Inspiral source reconstruction
• Timing accuracy and binary parameters dependence issue• Improvement obtained by requesting a mass correlation between
the 3 ITFs template triggers (pseudo coherent follow up)
Without asking any mass correlation in The 3 ITFs triggers
Fitted direction using the sametemplate for the 3 ITFs
M87
NGC
Inspiral search – open issues
• Timing estimation bias observed in LIGO / Virgo pipelines– Signal: time domain generation both for Virgo and
LIGO data sets– Template: LIGO: stationary phase approximation
(frequency domain)Virgo: Fourier transform of time domain templates
• MBTA / LIGO SNR ratio
Burst search - pipelines
• Time frequency– Power Filter (PF), Q Transform (QT), Kleine Welle (KW)
• Time domain– Mean Filter (MF), Alternative Linear Fit Filter (ALF)
• Correlators– Gaussian templates (PC), Complex Exponential Gaussian templates (EGC)
A battery of filters used to cover a large variety of possible waveforms.
– Performance comparison: different efficiencies according to the waveform“robustness” tests
– Can we gain by combining the different filters? AND/OR analysis?
Burst LIGO-Virgo network sky coverageSource in the direction of the Galactic center
24 hours
Virgo and LIGO ITFs do not see the Galaxy centerat the same time …
is there an interest of coincidence analysis?
Burst SNR seen in each ITF as function of time
Burst coincidence search resultsperformance of the HLV network
HL HV LV HLHVLV
41% 22% 22% 60%
H L V63% 60% 55%
• Example: A2B4G1 waveform• Single interferometer results:
– Best efficiency among 5 filters– False alarm rate 0.1 Hz
(~10 000 FA per day)
• Coincidence:– Require time (and frequency)
coincidence– Double coincidence:
• False alarm: 10-6 Hz
– Triple coincidence:• False alarm: 10-6 Hz HLV
19%
Adding Virgo to LIGO increases the network efficiency by ~50%
efficiency
efficiency
efficiency
Burst AND/OR analysis (on-going work)
OR: can we “recover” events by combining several algorithm triggers?
PRELIMINARY!
At high FAR (0.1Hz) :small efficiency increase
At low FAR: no gain …
Filter “robustness” tests Goal: assess filters performance over a class of signals spanning the
duration, central frequency and frequency band parameters
Band passWhite noise + SineGaussian
• Some signal location depends on the parameter’s definition …• A filter can have different efficiency response depending on the waveform …
shows that the 3 parameters do not fully describe a signal and/or the response of a filter …
Example: PF signal SNR=10
DFM
Burst source location
• 2 “classical” methods using arrival time and SNR information of triple coincidence triggers. (χ2 minimization and likelihood maximization).– Comparison to be done!– Talks of F. Cavalier & S. Klimenko
Example: burst from GC using the χ2 method using triple coincidence events over 24 hours (HLV eff=19%)
GC: α GC = 266.4˚ δGC = -28.98˚
Rec: α GC = 266.4˚ +/- 0.70˚ δGC = -28.98˚ +/- 0.97˚
angular error ~ 1˚
Present activities
• 2 papers in preparation containing all results obtained so far
• Coherent analysis: under test and/or development
Burst: – 2 LIGO pipelines (Likelihood and NULL streams methods)– 1 Virgo pipeline (J. Sylvestre PRD 68 (2003))
Inspiral: – 1 LIGO pipeline – 1 Virgo pipeline – LIGO: coherent inspiral parameter estimation (Markov chains)
S. Klimenko talkA. Searle talk
S. Bose, S. Dhurandhar & A. Pai Int. J. Mod Phys D9, 25 (2000)}
The next project: real data exchange
• Project 1 demonstrates the benefits and the feasibility of a joint data analysis
• Pipelines are ready both in LIGO and Virgo
Project 2: real data analysis! – 2a : exchange of 3 hours of data for technical validation (S4 and C7 f.i.)– 2b: exchange of 24 hours of coincident real data
coincidence and coherent burst and inspiral searches face real noise issues!
However, many issues still open:– which data? (similar sensitivity? or at least above few hundreds of Hz)
when? wait for Virgo is back this spring!– joint data analysis coordination: the LSC-Virgo data analysis group– publication policy?– detector knowledge spreading enhancement?
Conclusions
• Inspiral and burst pipelines succesfully tested (up to source location reconstruction)!• Coincidence analysis shows clear benefits to add Virgo to LIGO network.• Coherent analysis in progress …
Work scientifically sound!
Consensus for real data exchange in the next years !
Political agreements to be signed
Good prospect for joint data set and analysis in 2006