d2am2 heald cosmag - ska indico (indico) · 2017-05-19 · •rm grid: faraday rotation of...

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


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


CourtesyL.Rudnick

6 |

• RMGrid– ourHPSO• Band2largelyunaffectedincurrentplanning,somajorimpactnotanticipated• But,documulativereductionsinsensitivityimpingeontransformationalimpact?• Lossinbandwidthmeansmorethanmerelysensitivity(RMuncertainties)

• LOW• BothfrequencycoverageandBmax important,particularlyincombination

• MID• ImportanceofBand5forsupplementaryscience• NB:impactsonpulsarsciencearealsokeyformagnetismsciencecapability(pulsarsarehighlyeffectiveprobesoftheISM)

• SDP• Commensalityiskeyformagnetismobservations!

Take-homepointsformagnetism


StockholmKSObservationMatrix


• 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


10 |

• Improvedresolutionmaycriticallycombatbeamdepolarisationforresolvedsources,butthishasnotbeenquantified• Lowerλ2 (higherfrequency)maybecriticalforrecoveringpolarizedsourcepopulation(incasesaffectedbyafrequency-dependentdepolarizationmechanism)• Expectedriseinsourcecountstatisticsfrom250-350MHz;chartingthistransitionisnewandilluminatingscience!• Particularlybadtorestrictto<=250MHzifouterstationsarelost– wewouldstronglydisfavourthatcombinationofoptions

LOW:bandwidthabove250MHz


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


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


�RM / 1

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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


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


CosmicMagnetismSWGWorkshopPerth,ARRCbuilding– July17-212017• AttachedtoSKAPathfinderContinuumSurveys(SPARCS)meeting• SPARCSVII:ThePathfindersAwaken• http://www.icrar.org/conferences/sparcs7/

• Abstractdeadline:May12• Registrationdeadline:May30


SWGupdate

Progresswithpathfinder/precursorprojects


PrecursorandPathfinderSurveyProjects• LOFAR– polarization• MWA- polarization• ASKAP– POSSUM• MeerKAT– MIGHTEE• JVLA– VLASS

TechnicalandScientificpathfinderstoSKA1CMKSPs• Calibrationandimagingchallenges• dataplans,algorithmsandprocessing• Scientificdiscovery

SKA-LOW

SKA-MID


19 |

• More-or-lessroutineimagingw/36beamsnow

• Bandwidthalreadysufficientforpolarimetrytestingandearlyscience

ASKAP:Nextsteptothe“allsky”RMGrid

Anderson,Raja


20 |

• CentralportionofFornaxfield:

ASKAP:Nextsteptothe“allsky”RMGrid

ATCA(~250uJy /beamRMS) ASKAP(~60uJy /beamRMS)

Anderson,Raja


21 |

• On-axispolarisation calibrationmethodhasbeendeveloped.Initialresultslookpromising.

• LeakageofStokesIintoVestimatedat~0.3%forbrightsourceslocatedrandomlyinthefield

• HighdegreeofcommonalitybetweenlinearlypolarisedsourcesdetectedwithASKAP,andlinearlypolarised sourcesinothercatalogues(NVSSRMcatalogue,Andersonetal.2015ATCAFornaxfield)

• Detailedsourcepropertycomparisonsarenowunderway,withtheaimofquantifyingoff-axiseffects

ASKAP:Polarimetryprogress


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


CSIROAstronomy&SpaceScienceGeorgeHealdt +61864368758e [email protected] www.csiro.au

ASTRONOMYANDSPACESCIENCE

Thankyou

d2am2 heald cosmag - ska indico (indico) · 2017-05-19 · •rm grid: faraday rotation of...

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