VMC–theVISTAsurveyoftheMagellanicSystem

Metallicityofstellarpopula<onsMo<onofstellarpopula<ons

DrMaria‐RosaCioni

ESO spectroscopic survey workshop ESO-Garching, Germany, 9-10 March 2009

(Gal-Exgal survey)

TheVISTAsurveyoftheMagellanicSystem

M.Cioni,K.Bekki,G.Clemen<ni,W.deBlok,J.Emerson,C.Evans,R.deGrijs,B.Gibson,L.Girardi,M.Groenewegen,V.Ivanov,M.Marconi,C.Mastropietro,B.Moore,R.Napiwotzki,T.Naylor,J.Oliveira,V.Ripepi,J.vanLoon,M.Wilkinson,P.Wood

UnitedKingdom,Italy,Belgium,Chile,France,Switzerland,SouthAfrica,Australia http://star.herts.ac.uk/~mcioni/vmc/

Theteam

Themostsensi<venear‐IRsurveyacrosstheLMC,SMC,BridgeandpartoftheStream

ESO Public Survey 2009-2014

1.5 deg2

FOV

4m Telescope

≈180deg23filters‐YJKs15epochs(12inKSand3inYJ;oncesimultaneouscolours)S/N=10at:Y=21.9,J=21.4,Ks=20.3(Ks≈19singleepoch)Seeing0.8arcsec–averageSpa<alresolu<on0.34pix/arcsec(0.51arcsecinstrumentPSF)Servicemodeobserving1840hours/240nights

http://star.herts.ac.uk/~mcioni/vmc/

0.ObservetheMagellanicSystem

I.Derivethespa<allyresolvedSFH

Synthe<cdiagramofatypicalLMCstellarfieldasexpectedfromVMCdata.

Thisfieldcovers1VISTAdetector!

Accuracy:metallicity0.1dexandage20%in0.1deg2

Kerberetal2009

http://star.herts.ac.uk/~mcioni/vmc/

S/N=10

RRLyraestarsareexcellentdistanceindicatorsinthenear‐IR

Firstapplica<ontotheLMCbartoderivetheLMCdistance(Szewczyketal2008)–0.2kpcaccuracy

ThestructureoftheMagellanicSystemwillbemeasuredusingCepheidvariables,theredclumpluminosity,the<poftheredgiantbrach,etc.

II.Tracethe3Dstructureasafunc<onof<me

http://star.herts.ac.uk/~mcioni/vmc/

The LMC is a few kpc thick and the SMC up to 20 kpc

III.IV.V.VI.VII.VIII....

Stellar Clusters and other sub-structures Planetary Nebula and other emission line objects Obscured massive stars and pre-MS stars of a few MSun The differential proper motion The distance of the Large Magellanic Cloud Simulations of the Magellanic System Etc.

A unique counterpart for existing and planned (e.g. VST) optical surveys & mid-infrared Spitzer observations

Complementary to a survey of the outer region (8-20 kpc); the VISTA-VHS will cover this area (Ks≈18)

PNedetec<on The sample of PNe across the Magellanic Clouds is very incomplete

Current samples are biased to bright (young and asymmetric) PNe

Reid & Parker (2006) have doubled the number of PNe in the central 25 deg2

VMC will detect PNe from their colours; VMC spatial resolution - good

Ks includes Brγ with very little contamination by He

Brγ traces nebulae as Hα

Spectroscopic follow-up is required for confirmation

Themetallicity(iron+)asatracerofhistoryandstructure

  Primordial gas is metal-poor.   Enrichment is due to subsequent star formation, accretion or merging.   The distribution of gas is influenced by the structure and dynamics of the host galaxy.

What is the chemical history of the Magellanic System? How and when the Bridge and Stream formed? What is the depth of the Magellanic Clouds? Are they disc galaxies with a spheroidal halo? How and when these structures formed? Etc…

Themetallicitydecreaseslinearly;aflatoutergradient? RRLyraestars,metalpoorRGBstarsandoldstellarclusterstracethesamegradientasAGBstars(outerdisc/halo?) YoungRGBstarsandyoungstellarclustersshownogradient(bareffect?)

MetallicitygradientacrosstheLMC(Cioni2009,tbs)

MetallicitygradientacrosstheSMC(Cioni2009,tbs)

Stellarclusters(youngandold),AGBstarsandRGBstarsdonotshowasignificantgradient.Bareffect? ThemetallicityisconsistentwiththatintheBridge ThemetallicityoftheSMCisthesameasthatoftheLMCat4kpc(innerdisc/outerdiscorhalotransi<on?)

AnSMCmetal‐richring?

via optical colour-magnitude diagrams Harris & Zaritsky 2004

10.6 Gy 8.7 Gy 6.3 Gy 3.9 Gy 2 Gy via magnitude distributions of AGB stars Cioni et al 2006

Propagation of star formation? Accretion of satellite? Star forming episode induced by LMC interaction? Effect of bar? α elements or oxygen enhancement?

Aviablepicture(agreement/disagreement/largeerrors/models?):

TheMagellanicCloudsexperiencedtwomajorepisodesofstarforma<on:onemanyGyragoandone2‐4Gyrago

TheoldepisodeformedtheLMCouterdisc/haloandtheSMCbar.TherecentepisodeformedtheinnerLMCdisc,theLMCbarandinducedstarforma<onintheSMCring.

TheMagellanicStreamformedoutofLMCgasintherecentepisode:[Fe/H]=‐0.6dex(Niedeveretal2008).TheMagellanicBridgeformedoutofSMCgas.

TheSMCmayhaveabulge(Subramanian&Subramaniam2009).

TheMo<onofstellarpopula<ons Theageandchemistryofgroupsofstarsarenot

sufficienttodescribetheforma<onandevolu<onofthehostgalaxy

 Thedynamicalstateisneededtorecognizesub‐structuresthatshapedtheMagellanicSystem(bulge,halo,clustersvsfieldstars)

 Thespacemo<onrequiresboththeradialvelocityandthetangen<alvelocity

 Radialvelocityobserva<onsexistonlyforsubsetsofstarslimitedintypeorloca<on

Differen<alPropermo<on

Piatek et al 2008

PMindifferentfields(HST2yr)indicatesrota<onintheLMCandradialexpansionintheSMC

WhatisthePMinspaceand<me?ΔPM=0.8‐1mas/yramongdifferentfieldsVMCcanreachPMaccuracyof0.05mas/yrcomparablewithHSTfrommanystarsandreferenceobjectsperresolu<onelement(TBD)

SMC LMC

ExtractfromshoppinglistVMCwillnaturallyleadtospectroscopicfollow‐upstudies

MCsaretheclosestexampleofinterac<nggalaxiesMCsarealaboratoryforstellarevolu<on

VMCsurvey(2009‐2014)

 totalmetallicity‐error<0.1dex age‐error20%in0.1deg2 depth‐error0.2kpc propermo<onofdifferentpopula<ons‐error0.05mas/yr

Spectroscopicsurvey

 [Fe/H]withsmallerrors Measureαandotherelementsabundances Confirm/selecttargets MeasureradialvelocityGAIA(2011‐)Metallicity,radialvelocityandpropermo<onofbrightgiants

 Short‐term:low‐res/molecules;high‐res/limitedFoV/samples Long‐term:wide‐field/faintpopula<ons

Photometry&Spectra:

 structurevs<me chemistryvs<meandstructure globalevolu<on/simula<onofthesystem