Probing the Fast Radio Burst Population(s?) with CHIME · CHIME/FRB Collaboration UBC Dr. Davor...
Transcript of Probing the Fast Radio Burst Population(s?) with CHIME · CHIME/FRB Collaboration UBC Dr. Davor...
ProbingtheFastRadioBurstPopulation(s?)withCHIMESHRIHARSH P.TENDULKAR
+CHIME-FRBTEAM
Canadian Hydrogen Intensity Mapping Experiment
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CHIME/FRBCollaboration
UBCDr. Davor CubranicDeborah Good, PhD studentProf. Mark HalpernProf. Gary HinshawDr. Kiyo MasuiDr. Cherry NgProf. Kris SigurdsonProf. Ingrid Stairs
DRAODr. Tom LandeckerDr. Paul Scholz
Perimeter InstituteUtkarsh Giri, PhD studentDr. Dustin LangMasoud Ravandi, PhD studentProf. Kendrick Smith
WVUProf. Kevin Bandura
NRAODr. Paul DemorestDr. Scott Ransom
University of TorontoProf. Dick BondNolan Denman, PhD studentProf. Bryan GaenslerProf. Ue-Li PenAndre RecnikProf. Keith Vanderlinde
McGillDr. Michelle BoyceDr. Jojo BoyleShiny BrarProf. Matt DobbsDr. Emmanuel FonsecaProf. David HannaAlex Josephy, MSc studentProf. Vicky KaspiDr. Arun NaiduChitrang PatelZiggy Pleunis, PhD studentDr. Shriharsh Tendulkar
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Arewefightingonehorse-sizedduckor
ahundredduck-sizedhorses?
FRBZoo(Repetition)Aretheretwodistinctpopulationsofrepeatersandsinglebursts?
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Orisitasmoothdistribution?
Rateparameter
FRBpo
pulatio
n
RepeatersSinglebursts
Rateparameter
FRBpo
pulatio
n
RapidRepeatersRareRepeaters
Temporalclusteringmakesit*very*challengingtodrawconclusions(Opperman &Pen2017)
FRBdesert
Also,propagationaffectsdetectablerepetition.
FRBZoo(Polarization)Unpolarized/Lowpolarization
Stronglinearpolarization
Strongcircularpolarization
FRB140514— ~23%circ polzn(Petroff et al 2017)
FRB150215— 43%Polzn (Petroff et al 2017)
FRB150418— Lin polzn 8.5%(Keane et al 2016)
FRB150807— 80%Polzn (Ravi et al 2017)
FRB110523— 44%Polzn (Masui et al 2017)
FRB121102— 100%Polzn (Michilli etal2018)
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Noinformationabouttherest
5
FRBZoo(RadioFrequency)MostFRBsurveyshavebeenatLband(1.4GHz)◦ Reasonablywell-determinedrate
4detectionsat~800MHz(GBT+UTMOST)
Butnodetectionsat350MHzwiththeGBNCCsurvey(Chawlaetal2017)
Isthisduetofree-freeabsorption,scatteringorisitintrinsic?
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FRBZoo— Propagationeffects• Interveningmediumaffects• Intensity,• Scattering,hencedetectability• Alsopolarization
• Boostingduetodiffractivescintillation• Suppressionduetofree-freeabsorption
• Somestatisticalevidenceofhigherratesathighgalacticlatitudes(VanderWeiletal2016butseeMacquart+2018)
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21&
10
Figure 10. Simulation of detections vs Galactic coordinates. Thecolor scale shows the number of sources detected out of a total of1.5 ⇥ 1010 sources. The luminosities and distances of the popula-tion are set up so that no sources are detectable in the absence ofISS. The results are for a power-law ↵ = 0 with cutoffs of 100 and750 Jy Mpc2 and a homogeneous population between 50 and 2000Mreshold pc. The survey threshold is 0.3 Jy and bandwidth aver-aging has been included over a 300 MHz bandwidth centered on1.5 GHz. Reduction of survey sensitivity by temporal broadeninghas not been included, so that dearth of detections at low latitudestoward the inner Galaxy is more severe than is shown.
Figure 11. Number of detected sources vs. Galactic latitude, ob-tained by summing the values shown in Figure 10 over longitude.
sampled from the population distribution is ⌘Tng , so themean number of detections is
Nd,s = ⌘TngPL(Ssd2/gng )id (24)
The relevant value of gng (and thus ng) needs to be solvedfor to match Nd,s to the actual number of survey detections.
Figure 12. (Top) Plot of the number of survey trials vs. scintillationgain gng for the ng largest values in a survey. Eq. ?? is evaluated forISS with an exponential PDF for Nd,s = 10 and for different valuesof ru = Su/Ss, the ratio of the largest possible unscintillated fluxdensity to the survey threshold Ss. Burst amplitudes have a power-law PDF with a dynamic range RS = 103 and a power-law index↵ = 5/2. (Bottom) Upper limits on ⌘T from the lack of multipleburst detections in a survey observation that yields one burst on aparticular source. Different curves correspond to different values ofthe single-source ru1 . The single-source ampitude PDF is a powerlaw with ↵1 = 2 and dynamic range RS1 = 100.
Using ng = NgPg(gng ), the number of sampled sources is
n⌦⌦s =Nd,s
⌘TPg(gng )PL(Ssd2/gng )id(25)
which is an implicit equation for n⌦⌦s because gng dependson it. We therefore investigate the dependence of populationparameters on gng . This allows us to identify the minimum
population size required to explain survey results.
6.4. Exponential DISS
Though DISS with an exponential probability Pg(g >gng ) = e�gng is not realistic for surveys with bandwidthaveraging, it illustrates some important trends.
Figure 12 (top panel) shows Nevents,s plotted vs. gng forRS = 103, ↵ = 5/2, and several values of ru. There is aminimum value of Nevents,s at gng given by solving g↵�1
ng�
(↵ � 1)g↵�2ng
= r�(↵�1)u (for ↵ 6= 1). For ↵ = 2, gng =
1 + 1/ru.The curves of N (s)
events increase with gng for large gng be-cause a large population is needed to make large gng likely.The curves also increase at smaller gng when gngru ! 1 be-cause scintillated flux densities are then just above threshold,requiring large ⌘T to make a detectable amplitude probable.Thus the rate factor ⌘T must be large when ISS is small butat large gng , the population size must be large.
The no-ISS case discussed in § 4 corresponds to points onthe curves where gng = 1. Of course for ru < 1 there is
Detec.on&of&FRBs&favored&at&high&la.tudes:&&DISS&is&quenched&by&bandwidth&averaging&and&possibly&sourceRsize&suppression&&Simula.ons&include&luminosity&func.on,&steady&burst&rate,&and&DISS&with&bandwidth&averaging&(but&point&sources,&no&pulse&broadening)&&No&FRBs&detectable&without&DISS&
13/6/17 FRB Scintillations/Lensing: Near and Far
FigurefromJimCordes(Cordes etal,inpreparation)
Whatdowewant?*1. RateofFRBs(withagoodunderstandingofcompletenessandsensitivity)
1. Asafunctionofgalacticlatitude2. Asafunctionoffluence (w/otelescopebeampattern)3. AsafunctionofDMexcess
4. Asafunctionoffrequency(say,400-600MHzvs600-800MHz)
2. Repetition!1. Arethereotherrepeaters?2. Dotheyclusteratlowgalacticlatitudes?3. Ratesandtemporalclusteringproperties
3. Spectral,polarizationandscatteringproperties1. Distributionsandcorrelations
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*incompletelist
Howdowegetit?
1. Singlelargesurvey
2. Carefulinstrument+pipelinedesign
3. Sensitivitytestingandmonitoring
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CHIME:CanadianHydrogenIntensityMappingExperimentTransittelescopedesignedtostudyBaryonAcousticOscillationsatz=0.8-2.5
Four20mx100mcylinders
256dual-polfeedsoneachcylinder
400-800MHz
FOV:E-W~2.5o–1.3o,N-S~120o
Beamsize0.5o–0.3o
CFIfundedFRBbackendforreal-timedetection:“CHIME/FRB”
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≈220sq.deg.
CHIMEFRBRates
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FromP.Chawla
BasedonLawrenceetal2017rates(5.9× 102 sky−1 day−1 @1.4GHz,1Jy)
CHIMEisexpectedtodetect0.6-11FRBsperday (above10-sigma)
(andmoreat8-sigma)
FRBsandCHIMEWhatwewant CanCHIMEdeliver?
Thousandsofeventsforeventrate,fluxdistribution,angulardistribution,DMdistribution,scatteringvs DM,…
Yes
Repeatedobservations Yes
Real-time triggers Yesà GCN,VO, ATel Digest
Sensitivity topolzn vsfreq,vs time Yes
Localization:
Absolutelynecessaryfordistinguishing models
Arcminutes:WithinCHIME(SNRdependent)
Arcseconds: Maybe,ifoptical/X-raycounterparts exist,arelong-lived&brightORVLBI(downtheroad,outriggers?)
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CHIME
F-Engine F-Engine
Analogsignalchain
Digitizers+FPGAs
X-Engine X-EngineGPUcorrelator
CHIMECosmology CHIME-FRB CHIME-Pulsar
Eastandwestreceiverhuts
NorthandsouthGPUcans
1024freq channelsn2 visibilities30sec
16kfreq channels1024stationaryintensitybeams1-mssampling
1024freq channels10trackingvoltagebeams2.5-ussampling
13Tbps
130Gbps
• Cylinder focuses light only in EW direction
• Gives us large FOV2/26/18 SHRIHARSHTENDULKAR– FRB2018 14
• FFT telescope in NS direction
• 256 beams per cylinder2/26/18 SHRIHARSHTENDULKAR– FRB2018 15
\
• 1024 beams from full 4-cylinder CHIME
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CHIME-FRBPipeline
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L0node
L0 L1 L2 L3 L4FFTBeamforming1024intensitybeams
RFIremovalDedispersionMoreRFIrejection
Multi-beamgroupingMulti-beamRFIremovalLocalization
IdentificationActionchoice
DatabaseforheadersIntensitydataBasebanddataOfflineanalysis
L0node
L0node
L1Node
L1Node
L1Node
L2/L3Node Archiver+DB
Basebandcallback
Intensitycallback
128streams
64freq chanx8beams
Pulsartrackingbeam
Realtime (dispersionsweep+2-3seconds)AdaptedfromadiagrambyCherryNg
WorkbyC.Ng,K.Smith,M.Rafaiei,U.Giri,A.Josephy,SPT,P.Scholz,C.Patel,Z.Pleunis,E.Fonseca,S.Brar,P.Boyle,M.Boyce,V.Kaspi
Buffer Buffer
RFIexcision&filtering
ThreestagesofRFIdetection:Intensitydata,singlebeameventinformationandmulti-beaminformation
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Example
• Next step is “sifting”: we decide whether an event is astrophysical or RFI, based on its profile in the (DM, time) plane.
• Currently a placeholder until initial filtering is finalized.
• We expect that the computational cost will be very small, of order 0.01 cores/beam.
L1B code
M.Rafaiei,U.Giri,K.Smith A.Josephy SPT
Verynon-analyticselectioneffects!
KeepingtabsoncompletenessAcarefulpopulationstudyneedsanunderstandingofsensitivityandcompleteness.
Wewantto:
1. Maintaindetailed configurationhistorydatabase(re-runnable)◦ Whichsoftwareversion,whichconfiguration(bothversionedwithgit)
2. Runinjectiontestsinrealdatafortestingcompleteness
3. Logallinstrument&dataqualityparameters◦ Trackexposure,sensitivity
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LiveSensitivityTestingGoal
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L1’ L2’ L3’
L1’Node
L1’NodeL2’/L3’Node
InjectionServer
Copyof16beams
InjectFRBsintotheintensitydatawithfullbeammodel.Includebeamsensitivitywithfrequency,positionetc.Varyfluence,width,specidx
Exactlythesameconfiguration
Detections
Injections
Getsensitivity+completenessmeasurementEvery~10min
L0node
L0 L1 L2 L3 L4
L0node
L1Node
L1NodeL2/L3Node Archiver+DB
1024beams
LoggingDataQuality&Health
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L0node
L0 L1 L2 L3 L4
L0node
L1Node
L1NodeL2/L3Node Archiver+DB
1024beams
CentralLogger
#activefrequencychannels(sensitivity)#activefeeds(beamshape)ADCscaling(sensitivity)
#nodesalive(searchskyarea)L0-L1packetloss(sensitivity)RFImetrics(sensitivity,falsealarmrate)Spectrum,MaskFractionEvent/reject/acceptrate(sensitivity,sanitycheck)Processingdelays,latencies
L1nodedelays (sanitycheck)Eventrate (sanitycheck)Knownsourcesinthepasthour/day (sanitycheck)
L3/L4EventrateIntensitydatacallbackrateSuccessful/unsuccessfulactionsDiagnosticplots
MonitoringDashboards
Prometheus+Grafanabasedmonitoringdashboards• Fordataquality• Sanitychecks• Hardwarehealthchecks
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CHIME-FRBPilot
• Commissioninga8-nodepilotclusterwith64beamsonsky
• Thoroughlytestthesystemarchitectureandsoftwarepipeline
• 64beamsà 0.06– 0.6FRBsperday(1-10per2weeks,atLawrenceetalrates)
• Nodes+storageetc installedonsite.• Datapathtestedwithincoherentbeam.
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Crab
B0329+54
B0823+26
B1508+55
B2021+51
PRELIMINARY
52hourrunwiththeincoherentbeam~halftheCHIMEdesignbandwidth
B0329+54
PreliminaryRFIcleaning
Missingchannelsfilledwithmedianvalues
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PRELIMINARY
CHIMEStatus
•Workinghardtodebugandcommissionphase-coherentbeams
• Phasecoherentsolutionsbeingtestedaswespeak
• Acquiringfull128-nodesystem
Staytuned!
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