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AconciseoverviewoftheMaunakeaSpectroscopicExplorer

Version1.0,2016-05-27

AlanW.McConnachie1,2(MSEProjectScientist)

ScienceTeamContributors:CarineBabusiaux3,MichaelBalogh4,ElisabettaCaffau3,PatCôté2,SimonDriver5,AaronRobotham5,ElseStarkenburg6,KimVenn7,MatthewWalker8;ProjectOfficeContributors:StevenE.Bauman1,NicolasFlagey1,KevinHo1,SidikIsani1,MaryBethLaychak1,ShanMignot3,RickMurowinski1,DerrickSalmon1,DougSimons1,

KeiSzeto1,TomVermeulen1,KanoaWithington1

1CFHTCorporation,65-1238MamalahoaHwy,Kamuela,Hawaii96743,USA2NationalResearchCouncilofCanada,5071WestSaanichRoad,Victoria,BC,V9E2E7,Canada3GEPI,Obs.deParis,PSLResearchUniv.,CNRS,Univ.ParisDiderot,SorbonneParisCité;5PlaceJulesJanssen92195Meudon,France4DepartmentofPhysicsandAstronomy,UniversityofWaterloo,Waterloo,Ontario,N2L3G1,Canada5ICRAR,TheUniversityofWesternAustralia,M468,35StirlingHighway,Crawley,Australia,WA60096Leibniz-InstitutfürAstrophysikPotsdam(AIP),AnderSternwarte16,14482Potsdam,Germany7Dept.ofPhysicsandAstronomy,UniversityofVictoria,P.O.Box3055,STNCSC,VictoriaBCV8W3P6,Canada8McWilliamsCenterforCosmology,Dept.ofPhysics,CarnegieMellonUniversity,5000ForbesAve.,Pittsburgh,PA15213,USA

ThisshortdocumentisintendedasacompanionandintroductiontotheDetailedScienceCase(DSC)fortheMaunakeaSpectroscopicExplorer. ItprovidesaconcisesummaryoftheessentialcharacteristicsofMSEfromtheperspectiveoftheinternationalastronomicalcommunity.MSEis a wide field telescope (1.5 square degree field of view) with an aperture of 11.25m. It isdedicatedtomulti-objectspectroscopyatseveraldifferentspectralresolutionsintherangeR~2500–40000overabroadwavelengthrange(0.36–1.8μm).MSEwillenabletransformationalscienceinareasasdiverseasexoplanetaryhostcharacterization;stellarmonitoringcampaigns;tomographicmappingoftheinterstellarandintergalacticmedia;thein-situchemicaltaggingofthedistantGalaxy;connectinggalaxies to the largescalestructureof theUniverse;measuringthemassfunctionsofcolddarkmattersub-halosingalaxyandcluster-scalehosts;reverberationmappingof supermassiveblackholes inquasars.MSE is the largest groundbasedoptical andnearinfraredtelescopeinitsclass,anditwilloccupyauniqueandcriticalroleintheemergingnetworkof astronomical facilities active in the2020s.MSE is anessential follow-up facility tocurrentandnextgenerationsofmulti-wavelengthimagingsurveys,includingLSST,Gaia,Euclid,eROSITA,SKA,andWFIRST,andisanidealfeederfacilityforE-ELT,TMTandGMT.Contacts:

• CFHTExecutiveDirector:DougSimons(simons@cfht.hawaii.edu)• MSEProjectManager:RickMurowinski(murowinski@mse.cfht.hawaii.edu)• MSEProjectScientist:AlanMcConnachie(mcconnachie@mse.cfht.hawaii.edu)• MSEProjectEngineer:KeiSzeto(szeto@mse.cfht.hawaii.edu)

Moreinformation:

• The Detailed Science Case, Science Requirements Document and all original MSE sciencedocumentsareavailableathttp://mse.cfht.hawaii.edu/docs

• MoreinformationonMSEisavailableathttp://mse.cfht.hawaii.edu

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1 SystemOverviewMSEistherealizationofthelong-heldambitionoftheinternationalastronomycommunityforhighly multiplexed, large aperture, optical and near-infrared spectroscopy on a dedicatedfacility. Such a facility is the most glaringly obvious and important missing capability in theinternationalportfolioofastronomicalfacilities.MSEisarefurbishmentoftheCFHT,upgradedtoanapertureof11.25m.Figure1showstheoverallsystemarchitectureofMSE.

Figure1:Cut-awayofMSErevealingthesystemarchitectureandmajorsub-systems.

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2 TheCompositionandDynamicsoftheFaintUniverse

2.1 DefiningcapabilitiesTable1:SummaryofmajorsciencecapabilitiesofMSE.

MSEbuildsonthesuccessoftheSDSSconcept,butisrealizedonafacilitywith~20timeslargeraperturelocatedatpossiblytheworld’sbesttelescopesite.Definingsciencecapabilitiesinclude:• Survey speed and sensitivity: The etendue of MSE is > 2 larger than its closest 8m

competitor(149vs.66m2deg2forSubaru/PFS).MSE’ssensitivityallowsefficientobservationofsub-L*galaxiestohighredshift,andhighresolutionanalysisofstarsinthedistantGalaxy.Theexcellentsiteimagequalityisessentialtoobserveefficientlythefaintestobjectsandtoensurethespectrographopticsareareasonablesizegiventhemultiplexingdemands.

• Dedicatedandspecializedoperations:MSE’sspecializedcapabilitiesenableavastrangeofnew science. Specialized observingmodes allow time domain programs such as transienttargeting, quasar reverberation mapping and precision stellar radial velocity monitoring.Theserequirewell-calibratedandstablesystemsonlypossiblewithdedicatedfacilities.

• Spectralperformance:TheextensivewavelengthcoverageofMSEfromtheUVtoH-banduniquelyenables thesametracers tobeusedtostudygalaxyandblackholegrowthatallredshiftstobeyondcosmicnoon.ChemicaltaggingwithMSEcanbeconductedacrossthefullluminosityrangeofGaiatargets,andoperationatR=40000enablestheidentificationofweaklinesinthebluetoaccessspeciessamplingadiverserangeofnucleosyntheticsites.

2.2 KeyscienceprogramsTheScienceRequirementsforMSEaredefinedasthecapabilitiesnecessarytoconductasuiteofScienceReferenceObservations,highimpactscienceprogramsthatareuniquelypossiblewithMSE. These span exoplanetary host characterization to next generation cosmological surveys.WesummarizeasmallsubsetoftheseprogramstogiveaflavorofthediversesciencethatMSEenables,andreferthereadertotheDSCforamorecomprehensivedescription.

AccessibleskyAperture(M1inm)Fieldofview(squaredegrees)Etendue=FoVxπ(M1/2)2

Modes Moderate IFU

0.36-0.95μm J,Hbands 0.36-0.45μm 0.45-0.60μm 0.60-0.95μmSpectralresolutions 2500(3000) 3000(5000) 6000 40000 40000 20000Multiplexing >3200

Spectralwindows ≈Half λc/30 λc/30 λc/15

Sensitivity m=23.5*

Velocityprecision 9km/s�Spectrophotometicaccuracy <3%relative♯Dichroicpositionsareapproximate

*SNR/resolutionelement=2 � SNR/resolutionelement=5

♮ SNR/resolutionelement=10 ★SNR/resolutionelement=30

Wavelengthrange 0.36-0.95μm0.36-0.95μm�0.36-1.8μm

Low High

IFUcapable;anticipatedsecond

generationcapability

30000squaredegrees(airmass<1.55)11.25m1.5149

>1000

m=20.0�m=24*20km/s�

<3%relative

Full>3200

<100m/s★N/A

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2.2.1 Exoplanetsandstellarastrophysics

MSEwillprovidespectroscopiccharacterizationathighresolutionandhighSNRofthefaintendof the PLATO target distribution (g~16), to allow for statistical analysis of the properties ofplanet-hosting stars as a function of stellar and chemical parameters. With high velocityaccuracyandstability,MSEtimedomainspectroscopicprogramswillallowforhighlycomplete,statisticalstudiesoftheprevalenceofstellarmultiplicityintotheregimeofhotJupitersforthisand other samples and also directly measure binary fractions away from the SolarNeighbourhood. A menagerie of rare stellar types will be identified in MSE multi-epochspectroscopic datasets that will allow for population studies of in-situ stars across allcomponentsoftheGalaxy,atallgalactocentricradiiandatallmetallicities.

2.2.2 ChemicaltaggingintheouterGalaxy:thedefinitiveGaiafollow-up

Figure2:MainpanelshowstherelativefluxofasyntheticspectrumofametalpoorredgiantstarattheintermediateMSEspectralresolutionofR~6000,alongwithsomeof thestronglinestellardiagnosticsaccessibleatthisresolution.Highlightedregionsshowthenormalizedfluxinthreewindowsobservablewith the high resolutionmode of MSE. Amagnified region of the UV window shows examples of thespecies that will be identified at high resolution. MSE chemical tagging surveys will identify speciessamplingalargeanddiversesetofnucleosyntheticpathwaysandprocesses.

MSEwill haveanunmatchedcapability for chemical taggingexperiments.Recentwork in thisfieldhasstartedtorevealthedimensionalityofchemicalspaceandhasshownthepotentialforchemistrytobeusedinadditionto,orinsteadof,phasespace,torevealthestellarassociationsthat represent the remnants of the building blocks of the Galaxy. MSE will push thesetechniques forward to help realize the “New Galaxy”, as originally envisioned by Freeman &Bland-Hawthorn (2002, ARA&A, 40, 487). MSE will focus on understanding the outercomponentsoftheGalaxy–thehalo,thickdiskandouterdisk–wheredynamicaltimesarelongand whose chemistry is inaccessible from 4-m class facilities. These components will be

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decomposedintotheirconstituentstarformationeventsbymeasuringabundancesofchemicalspecies that tracea largenumberofnucleosyntheticpathways.This includes rare speciesandheavyelementsatbluewavelengthsthroughR40Kcapabilities(Figure2).MSEistheonlyfacilitycapableofhighresolutionstudiesofstarsacrossthefullluminosityrangeofGaiatargets.

2.2.3 TheDarkMatterObservatory

Figure3:Recoveryofline-of-sightvelocitydispersion(left)anddarkmatterdensity(right)profilesasafunctionof stellar spectroscopic sample size fordwarf galaxies, demonstrating theneed for extensivedatasetswithMSE.Shadedregionsrepresent95%credible intervals fromastandardanalysisofmockdatasetsconsistingofradialvelocitiesforN=102,103and104stars(medianvelocityerrorsof2kms−1),generatedfromanequilibriumdynamicalmodelforwhichtrueprofilesareknown(thickblacklines).

MSEis theultimatefacility forprobingthedynamicsofdarkmatteroverallspatialscales.ForMilkyWaydwarfs,MSEwillobtaincompletesamplesoftensofthousandsofmemberstarstoverylargeradiusandwithmultipleepochstoremovebinarystars.Suchanalyseswillallowtheinternaldarkmatterprofiletobederivedwithhighaccuracyandwillprobetheoutskirtsofthedark matter halos accounting for external tidal perturbations as the dwarfs orbit the Galaxy(Figure3).AnewregimeofprecisionwillbereachedthroughthecombinationofwidefieldMSEradialvelocitysurveyswithprecisionastrometricstudiesofthecentralregionsusingE-ELT,TMTand GMT. In the Galactic halo, high precision radial velocitymapping of every known stellarstream will reveal the extent of heating through interactions with dark sub-halos and placestronglimitsonthemassfunctionofdarksub-halosaroundanL*galaxy.Onclusterscales,MSEwillusegalaxies,planetarynebulaeandglobularclustersasdynamicaltracerstoprovideafullyconsistentportraitofdarkmatterhalosacrossthemassfunction.

2.2.4 TheconnectionbetweengalaxiesandthelargescalestructureoftheUniverseWithin the ΛCDM paradigm, it is fundamental to understand how galaxies evolve and growrelative to thedarkmatterstructure inwhichtheyareembedded. This requiresmappingthedistributionofstellarpopulationsandsupermassiveblackholestothedarkmatterhaloesandfilamentary structures that dominate themass density of theUniverse, and to do so over allmassandspatialscales.MSEwillprovideabreakthrough inextragalacticastronomyby linking

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theformationandevolutionofgalaxiestothesurroundinglarge-scalestructure,acrossthefullrangeofrelevantspatialscales(fromkiloparsecstomegaparsecs).AlocalgalaxysurveywithMSEoutto100Mpccouldsampleourneighbourhooddowntothelowestdetectablemassesof3x105M

¤allowingforacompletecensusofmassinthelocal

Universe.Adeepnearinfraredselectedspectroscopicsurveywouldbeabletomeasurevelocitydispersionmassesforsystemsanalogoustothelocalgroupouttoz=1,i.e.,theMW,M31andM33wouldallbedetectable.Thiswillprovideadirectmeasurementofdarkmatterassemblyfor>1012M

¤halosoverhalftheageoftheUniverse.Themostmassivehaloscouldpotentially

betracedtoz=5,wherethedetectionofanysuchhaloswouldpresentmajorproblemsfortheColdDarkMatterparadigm.MSEwillfollowgalaxyevolutionacrossthepeakinstar-formationandmergeractivity,andtracethetransitionfrommerger-dominatedspheroidformationtothegrowthofdisks(Figure4).

Figure4:Leftpanel:ConeplotshowinganillustrativeMSEsurveycomparedtoothernotablebenchmarkgalaxy surveys. Cones are truncated at the redshift at which L* galaxies are no longer visible. Rightpanels: Lookback time versus cosmic star formation rate (right axis) using the parameterization ofHopkins&Beacom(2006,ApJ,651,142).GreylinesindicatethewavelengthofOII3727Å.Alsoindicatedon thiswavelengthscale is thewavelengthcoverageof themajorhighlymultiplexedspectrographs indevelopment.Theseareoffsetaccordingtotheirsystemetendue(leftaxis).ThelightconedemonstratesthereachofMSEforextragalacticsurveysusingahomogeneoussetoftracersatallredshifts.

2.2.5 TransienttargetingwithMSESpectroscopic follow-up is essential to understanding the time-variable events discovered byLSST, SKA and other all-sky transient surveys. MSE transient studies take advantage of thededicated operation of the facility to accumulate large datasets over time with only a smallfraction of science fibres ever dedicated to targets. IfN fibres in everyMSE pointing observerecently identified transients (e.g., within the past 24 hours), the observing efficiency of themainMSEsurveywilldecreaseby~[N/3200].However,thegaintotransientsciencewillbetheequivalentofN largeaperture telescopesdoingnothingbut transient spectroscopywith theirsingleobjectspectrographs. LSSTwill image ~1500deg2pernightaccessibletoMSE, inwhich

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therewill be~300newsupernovaeand>75000variable stars (Ridgwayet al. 2014,ApJ, 796,53).MSEwilldominatetheregimeoffainttransientsanditwillbeabletodedicatemoretimetotransientspectroscopythananyotherlargeaperturetelescope.

2.2.6 ThegrowthofsupermassiveblackholesMSEwill allowanunprecedented,extragalactic timedomainprogram tomeasuredirectly theaccretionratesandmassesofalargesampleofsupermassiveblackholesthroughreverberationmapping.Thisinformationisessentialforunderstandingaccretionphysicsandtracingblackholegrowthovercosmic time.Reverberationmapping is theonlydistance-independentmethodofmeasuringblackholemassesapplicableatcosmologicaldistances,andonly~60local,relativelylow-luminosity AGN currently have measurements of their black hole masses based on thistechnique.MSEwillbreaknewgroundwithacampaignof~100observationsof~5000quasarsover a period of several years (totaling~600 hours on-sky). These observationswillmap theinnerparsecofthequasarsfromtheinnermostbroad-lineregiontothedust-sublimationradius.MSEwillrevealthestructureandkinematicsintheimmediatesurroundingofalargesampleofsupermassiveblackholesactivelyaccretingduringthepeakquasarera.

3 MSEandtheInternationalNetworkofAstronomicalFacilitiesAstronomyhasenteredthemulti-wavelengthrealmofbigfacilities.Figure5showssomeofthenewobservatoriesthatcollectivelyrepresentbillionsofdollarsof investment.Eachfacilitycanoperateonastand-alonebasis.However,recenthistorydemonstratesthatitisthecombinationof data from these facilities that will produce many of the major scientific advances. MSEoccupies a critical hub in the emerging network of international astronomical facilities,whichwilldefinethefutureoffrontlineastrophysicsinthe2020sandbeyond.MSE takes advantage of its equatorial location (ℓ = 19.8°𝑁) to access the entire northernhemisphereandmorethanhalfof thesouthernhemisphere (airmass<1.55). Itwill share thesameskyasSubaru/HyperSuprimeCam;will leverage theextensivemulti-wavelengthmappingofthenorthernskiesalreadyin-hand;willaccessmorethanhalf(>10000squaredegrees)ofthemain LSST footprint (with the ecliptic survey and any northern extensions increasing thisoverlap);willsharetwothirdsoftheSKAsky;willoverlapsignificantlyinaccessibleskywithE-ELT,TMTandGMT;willprovideaground-basedcomplementtotypicallythreequartersofthesurveyareaoffuturespacemissions,includingGaia,Euclid,WFIRST,eROSITA,SPICAandPLATO.

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Figure5:MSEandotherprominentastronomical facilities in the2020sandbeyond.ThenumberandtypeofastrophysicaltargetsaccessibletoMSEaredescribedintheinsetpanels.

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4 ScienceOperationsandDataProductsMSE isadedicatedspectroscopic survey facility foroperationby itspartnercommunities.Theprimedeliverableisdata,obtainedthroughoneormoresurveyprograms.Atfirstlight,baselinescienceoperationsanticipatealargelegacysurveydesignedbythescienceteam(comprisedofadark–extragalactic–andbright–Galactic–component)thatwilloccupyallavailableobservingtime.Onceinstandardoperation,observingtimewillbemadeavailableforadditionalstrategicsurveys of flexible scope. The impact, productivity, and allocations of legacy and strategicsurveyswillbereviewedcontinuallytorespondtocommunityneedsandsciencedevelopments.Data will be available immediately to the survey teams that work with the Observatory toprovide data products for theMSE community on a short timescale. A significant proprietaryperiodonsciencedataenablestheMSEcommunitytousethedataforfrontlinesciencebeforetheirworldwiderelease.TheMSEcommunityisservedbytheirabilitytoproposefor,designandleadambitioussurveyprograms,andbyaricharchiveofdataaccessibletoMSEastronomersforscientificexploitation. It isexpectedthat>5millionastronomicalspectrawillbe ingested intothearchiveonayearlybasis(roughlyequivalenttoaSDSSLegacySurveyevery3–4months).Thescientificadvantagesprovidedtothesecommunitiesarethereforesignificant.The design of MSE foresees the need to upgrade components or instruments over the longlifetime of theObservatory and to respond to a changing scientific landscape. Amulti-objectintegralfieldunitisalreadyanticipated,andthetop-endisdesignedtobeupgradabletodeliverthiscapability.MSEwill remaintheworld’spremierresourceforastronomicalspectroscopy:aspecializedtechnicalcapability,andageneralpurposesciencefacility.

5 DevelopmentofMSE

MSE is a rebirth of the 3.6m Canada-France-Hawaii Telescope as a dedicated, 11.25m,spectroscopic facility within an expanded partnership extending beyond the originalmembership. The Mauna Kea Comprehensive Management Plan anticipates CFHTredevelopment.MSEwill reuse thecurrentbuildingandpier (minimizingworkat thesummit)and theground footprintwill remain thesame.A renderingof thecurrentCFHT facilityandaconceptualrenderingoftheMSEfacilityareshowninFigure6.

MSEisconductingDesignPhaseStudiesthatwillleadtoaConstructionProposalReviewin2018–2019. InadditiontoCanada,FranceandHawaii,workpackagesforconceptualdesignsofallmajorsubsystemsarecurrentlydistributedamong institutesand industries inAustralia,China,IndiaandSpain.TheScienceTeamhas>100membersdistributedacrossthiscollaborationandextendstoseveralothernations.NewcollaboratorstotheprojectareencouragedtoparticipateinboththescienceandtechnicalaspectsofMSEdesign.

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Figure 6: The left panel shows a rendering of the current CFHT facility and the right panel shows aconceptualrenderingoftheMSEfacility.

MSEwillbenefit fromCFHT's40yearsofexperienceonMaunakeaanda support staffdeeplyrooted in theHawaii Islandcommunity.CFHT/MSE isactivelyengaging theHawaii communitythroughout the planning process and is committed to balancing cultural and environmentalinterests in the design of the observatory and the organization of the new partnership.Withtheirsupport,MSEwillbeginconstructiononceithaspassedtheConstructionProposalReviewand the MSE partnership approves funding, and once all necessary permitting and legalrequirements have been fulfilled. This includes the approval of a new master lease for theMaunaKeaScienceReserve.