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CosmicMagnetismImpactofcostcontroloptions,andSWGupdate
CSIRO ASTRONOMYANDSPACESCIENCE
GeorgeHealdOnbehalfoftheCosmicMagnetismScienceWorkingGroup(chairs:AnnMao&RussTaylor)19May2017
• Stellarevolution• pulsars andcollapsedstellarobjects• Jovianplanets• cloudcollapse&starformation• stellaractivity&outflows
• Galaxyevolution• ISMturbulenceandenergytransport• stabilityofgalacticdisks• acceleration,propagation&confinementofcosmicrays
• Inter-Galacticphenomena• energytransportingalaxyclustermedia• AGNandIGMfeedback
CosmicMagnetismMagnetismiscentraltoastrophysicsonallscales
Cosmicmagnetism|GeorgeHeald2 |
CMKeyScienceProjects1. OriginandEvolutionofMagneticFieldsinLargeScaleStructures
(Mpc scales)• TheMagneticFieldinclusters,filamentsandtheirevolution• Magneticcosmicweb• ProbingtheNatureofDarkMatterandFundamentalPhysics
2.OriginandEvolutionofMagneticfieldsinGalaxies(kpc,<kpcscales)• Emergenceandevolutionofmagneticfieldsingalaxiesfrom
absorptionandemissionexperiments• Broad-bandpolarimetryasaprobeofAGNPhysicsatallredshifts
andluminosities• MagneticFieldsinNearbyGalaxies• Multi-scalemagnetismintheMilkyWay
3. MagneticFieldsandstellarevolution(stellarscales)• Roleofmagneticfieldsinstarformation,stellarevolution,
exoplanets
Cosmicmagnetism|GeorgeHeald3 |
4 |
• Pol.Synchrotronemission• RMGrid:Faradayrotationofbackgroundextragal sources
• Broadbandradiopolarimetryopensabrandnewwindow:• ImplementationofnewalgorithmsComplementaryuseofRMSynthesis&qu-fitting
• Characterise Bfields,densityandturbulenceinarangeofdifferentobjects
• 19magnetismsciencechaptersintheSKAsciencebook
HPSO:SKA1-MIDBand2RMGrid
Cosmicmagnetism|GeorgeHeald
5 |
• Nominalcharacteristics:• Band2,950-1760MHz• rms 4µJy/beam• resolution2”• goal:7-14millionRMs– EitherfromSDP,orpost-processing
HPSO:SKA1-MIDBand2RMGrid
Cosmicmagnetism|GeorgeHeald
CourtesyL.Rudnick
6 |
• RMGrid– ourHPSO• Band2largelyunaffectedincurrentplanning,somajorimpactnotanticipated• But,documulativereductionsinsensitivityimpingeontransformationalimpact?• Lossinbandwidthmeansmorethanmerelysensitivity(RMuncertainties)
• LOW• BothfrequencycoverageandBmax important,particularlyincombination
• MID• ImportanceofBand5forsupplementaryscience• NB:impactsonpulsarsciencearealsokeyformagnetismsciencecapability(pulsarsarehighlyeffectiveprobesoftheISM)
• SDP• Commensalityiskeyformagnetismobservations!
Take-homepointsformagnetism
Cosmicmagnetism|GeorgeHeald
StockholmKSObservationMatrix
Cosmicmagnetism|GeorgeHeald7 |
• Needscience-drivendetailedspecifications• ComplementaritywithKSOsforotherKSPs
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Scienceprojectindex&overview
8 | Cosmicmagnetism|GeorgeHeald
Goal RMGrid2 Extras Time Area
KSP1
1 Themagneticfieldinclustersandfilaments Yes LOW+1 2000 30k(+)
2 ProbingthenatureofDarkMatter Yes Targeted 3000 10
3 Themagneticcosmicweb Yes Deep1,2 1000 100
KSP2
4 LoS probesofevolutionofcosmicmagnetism Yes Band3?
5 Emergenceandevolutionofthemagneticfieldsingalaxydisks(andhalos)
No Deep 2 4300 10
6 Broad-bandpolprobing AGN/Galaxyphysics Yes Max λ2 5000 30k
7 MagneticfieldsinAGNatallzandluminosities Yes VLBI
8 EmergenceofmagneticfieldsintheUniverse Yes LOW+1 2-4k 30k
9 Magneticfieldsinnearbygalaxies Yes Deep2,5 4-6k 25-30
10 MagneticfieldsintheheartoftheMilkyWay Yes Deep1,2,5 3000 4k
11 Multi-scalemagnetismintheMilkyWay Yes Deep1 30k
KSP3 12 Role ofmagneticfieldsinstellarevolution
9 |
• 5.31:Reducebandwidth300->200MHzSubstantialreductioninλ2 coverageLargeimpactforscienceprojects1,8(clusters,emergenceofmagnetism)
• 2:Dipoledesign(logperiodicvsdipole)primaryimpactthrougheffectonavailable/sensitivebandpass
• 5.30.0:Bmax reductionto50or40kmReducedresolutionismorecriticalforLOWthanforMIDImpactsparticularlycluster/filamentscience(project1)particularimpactifcombinedwithreducedbandwidthoption
• 5.30:Remove54or108stationsfromcoreLose20-40%ofsurfacebrightnesssensitivityParticularimpactfor1(cluster/filaments),also8(emergence)
Costcontroloptions:LOW
Cosmicmagnetism|GeorgeHeald
10 |
• Improvedresolutionmaycriticallycombatbeamdepolarisationforresolvedsources,butthishasnotbeenquantified• Lowerλ2 (higherfrequency)maybecriticalforrecoveringpolarizedsourcepopulation(incasesaffectedbyafrequency-dependentdepolarizationmechanism)• Expectedriseinsourcecountstatisticsfrom250-350MHz;chartingthistransitionisnewandilluminatingscience!• Particularlybadtorestrictto<=250MHzifouterstationsarelost– wewouldstronglydisfavourthatcombinationofoptions
LOW:bandwidthabove250MHz
Cosmicmagnetism|GeorgeHeald
11 |
• 5.24.1-3:reductionofBmax from150to120km• Nominalresolutionreducedby20%,
andperhapsmoreimportantlyaneffectivelossofsensitivity• Resolutiondirectlyimpacts6individualprojectstargetingsingleobjects
• 5.13.2/5.35:Band5bandwidthreducedto2.5or1.4GHz• largereductioninλ2 coverage• impactprojects9,10(galaxies,MilkyWay);hugeincreaseinsurveytime
• 5.5.2:Band5onlyinspiralarms,notincore• Lossofsurfacebrightnesssensitivity• Strongimpacton9,10(criticalquestioniswhetherSKA1remainstransformationalcf JVLA)
• 5.24:Remove11or22dishesfromcorearea• decreasecoresensitivityby10-20%• Impactseveryprojectthatprobesextendedemission;esp.MW,MC,CenA,NG
• 5.5.1,2:removeallband1or5• Eliminatesallsciencerequiringthosefrequencyranges(clusters/fil.,emergence,galaxies)
Costcontroloptions:MID
Cosmicmagnetism|GeorgeHeald
12 |
• Generally,magnetismcallsforlargeλ2 coverage(forimprovedRMprecision)
• ShiftingtohigherportionofBand2(by250MHz,tocombatconfusion)resultsinRMerrordegradingfrom2.8to4.9rad/m2
– Lossofabilitytodetectandprobeweakmagneticfields(e.g.nG forfilaments)– RemovalofforegroundRMsisalsoimpacted!(twofoldimpactonRMerrors)– Ifsystematicuncertaintieshavetobecompensatedbyaveragingovermanysources,thenweloseRMGridinformationatsmallangularseparation(loseprobesofsmallscalephysicalstructureinnearbyobjects,anddistantsources)
MID:impactofbandpass&reductions
Cosmicmagnetism|GeorgeHeald
�RM / 1
��2
1
2 · (S/N)
Hammond+(2012)
13 |
• SDP-HPCcapabilitytoenablemulti-purposedataprocessing• Strongdesiretoretainabilitytoaccommodatepolarisation workontopof“main”purpose
• Anticipatetheabilitytoperformpost-processinginregionalcentres
• 8:Deploy200,150,100,50Pflops• WorryintheSWGthatobservationsintendedtobepursuedcommensallywillbemorestronglyimpacted
• CommensalityanticipatedwithHI– e.g.nearbygalaxies,aswellascontinuumsurveys,forexample.• Related:howtomanagejointlyagreedselectionofcentralfrequency,inthelightofpotentiallycompetinginterestsregardingconfusion/localisation (totalintensity)vsRMprecision(polarization)?
Commensality:SDPandothereffects
Cosmicmagnetism|GeorgeHeald
Impacttable
14 | Cosmicmagnetism|GeorgeHeald
Goal LOWBW
LOWBmax
LOWcore
MIDBmax
MID5BW
MID5core
MIDcore
MIDB15
SDP
KSP1
1 Themagneticfieldinclustersandfilaments
2 ProbingthenatureofDarkMatter
3 Themagneticcosmicweb
KSP2
4 LoS probesofevolutionofcosmicmagnetism
5 Emergenceandevolutionofthemagneticfieldsingalaxydisks(andhalos)
6 Broad-bandpolprobing AGN/Galaxyphysics
7 MagneticfieldsinAGNatallzandluminosities
8 EmergenceofmagneticfieldsintheUniverse
9 Magneticfieldsinnearbygalaxies
10 MagneticfieldsintheheartoftheMilkyWay
11 Multi-scalemagnetismintheMilkyWay
KSP3 12 Role ofmagneticfieldsinstellarevolution
=moderateimpact
=strongimpact
15 |
• RMGrid– ourHPSO• Band2largelyunaffectedincurrentplanning,somajorimpactnotanticipated• But,documulativereductionsinsensitivityimpingeontransformationalimpact?• Lossinbandwidthmeansmorethanmerelysensitivity(RMuncertainties)
• LOW• BothfrequencycoverageandBmax important,particularlyincombination
• MID• ImportanceofBand5forsupplementaryscience• NB:impactsonpulsarsciencearealsokeyformagnetismsciencecapability(pulsarsarehighlyeffectiveprobesoftheISM)
• SDP• Commensalityiskeyformagnetismobservations!
Take-homepointsformagnetism
Cosmicmagnetism|GeorgeHeald
CosmicMagnetismSWGWorkshopPerth,ARRCbuilding– July17-212017• AttachedtoSKAPathfinderContinuumSurveys(SPARCS)meeting• SPARCSVII:ThePathfindersAwaken• http://www.icrar.org/conferences/sparcs7/
• Abstractdeadline:May12• Registrationdeadline:May30
Cosmicmagnetism|GeorgeHeald16 |
SWGupdate
Progresswithpathfinder/precursorprojects
Cosmicmagnetism|GeorgeHeald17 |
PrecursorandPathfinderSurveyProjects• LOFAR– polarization• MWA- polarization• ASKAP– POSSUM• MeerKAT– MIGHTEE• JVLA– VLASS
TechnicalandScientificpathfinderstoSKA1CMKSPs• Calibrationandimagingchallenges• dataplans,algorithmsandprocessing• Scientificdiscovery
SKA-LOW
SKA-MID
Cosmicmagnetism|GeorgeHeald18 |
19 |
• More-or-lessroutineimagingw/36beamsnow
• Bandwidthalreadysufficientforpolarimetrytestingandearlyscience
ASKAP:Nextsteptothe“allsky”RMGrid
Anderson,Raja
Cosmicmagnetism|GeorgeHeald
20 |
• CentralportionofFornaxfield:
ASKAP:Nextsteptothe“allsky”RMGrid
ATCA(~250uJy /beamRMS) ASKAP(~60uJy /beamRMS)
Anderson,Raja
Cosmicmagnetism|GeorgeHeald
21 |
• On-axispolarisation calibrationmethodhasbeendeveloped.Initialresultslookpromising.
• LeakageofStokesIintoVestimatedat~0.3%forbrightsourceslocatedrandomlyinthefield
• HighdegreeofcommonalitybetweenlinearlypolarisedsourcesdetectedwithASKAP,andlinearlypolarised sourcesinothercatalogues(NVSSRMcatalogue,Andersonetal.2015ATCAFornaxfield)
• Detailedsourcepropertycomparisonsarenowunderway,withtheaimofquantifyingoff-axiseffects
ASKAP:Polarimetryprogress
Cosmicmagnetism|GeorgeHeald
22 |
• VLASkySurvey(VLASS)• A21stcenturyversionoftheNVSSandFIRST,all-skyabovedeclination−40o.• Resolution:2.5”(Bconfiguration),covering2-4GHz• RMS:69μJy/beam(co-addedover3epochs)• Observations:2017-2024• Mainscienceprograms:polarisation,time-domainscience• MIGHTEE(MeerKAT)• MIDL-band(2uJy,18sq deg),S-band(1uJy,5sq deg)• DEEPL-band&UHFto0.1uJy (1sq deg,commensalwithLADUMA)
Otherkeyforthcomingpolarizationplans
Cosmicmagnetism|GeorgeHeald
CSIROAstronomy&SpaceScienceGeorgeHealdt +61864368758e [email protected] www.csiro.au
ASTRONOMYANDSPACESCIENCE
Thankyou