TheMetallicityGradientsintheDisksFromSEGUE

JenniferJohnsonOhioStateUniversity

Outlineoftalk

•  OverviewofSDSS/SEGUEsurvey•  MetallicitygradientsfromSEGUE– RadialgradientfromCheng,etal.2012

– VerticalgradientfromSchlesinger,etal.2012

•  APOGEEandseismology– APOKASC– CoRoT

SEGUEFootprint

Yannyetal.2009

SloanDigitalSkySurveyOverview

•  Eachplateobserves7squaredegrees•  Varietyoftargetcategories– Colorandmagnitudecutsfromphotometry

•  StellarspectraprocessedthroughtheSSPP(Leeetal.2011)

•  AllSEGUE/SEGUE2datanowreleased•  ImprovementsinstellarparametersinDataRelease9

SEGUESurveyInPerspective

•  Nowoutsidethesolarneighborhood–notoneMDF

•  Nokinematicoralphaselectionused(forthesestudies)

•  Fainterstars=lowerresolution(R~18000)abundanceinformationconsiderablyless

•  Targetselectionalgorithmbasedonpublicdata

CorrectingforSelectionBiases

•  Incompletesampling– Functionofl,b

•  Magnituderangenotsampledproportionally

•  Colorcutscorrespondtodifferentmassrangesdependingonmetallicity

•  Ageeffects(notaproblemfortheG/Ksample)

•  Correlateddistance/metallicityerrors

•  Testingby“observing”models

RadialMetallicityGradientChengetal.2012

•  22low‐latitudeplatesyielding7010stars•  Bluecolorcut•  Distancessensitivetoage•  SpectroscopicparametersforTeff,logg,and[Fe/H]usedbecauseofhighandvariablereddening

•  TestedonGalacticmodels

LocationofSampleinR‐Zplane

AgeImpactsonDistances

RadialGradientchangeswithZ

VerticalMetallicityGradientSchlesingeretal.2012

•  GandKstarswereheavilytargetedbySEGUE•  “Gdwarfs”– 0.48<g‐r0<0.55– 24,270starswithS/N>10– 1.59‐2.29kpcfor“volumecompleteness”

•  “Kdwarfs”– 0.55<g‐r0<0.75– 16,847starswithS/N>10– 1.19‐1.84kpcfor“volumecompleteness”

Correctingfortargetselection

GCSandSEGUEcomparison

RadialGradient‐‐AgreeswithChengetal.2012

MDFasafunctionofheight

Shiftduetoincreasingα‐richpopulation

AlphahistogramsfromLeeetal.2011

StrongdisagreementwithGalacticmodels

AGES

•  Powerfultestofdiskformation/evolutionmodels

•  Openclusterprovideaccurateages,butdonotcoverallofparameterspace

•  GreathopefromGaia–bothdirectandindirectimprovementinages

•  APOGEE+asteroseismologyforredgiantages

AgesforRedGiants

•  Redgiantsareluminousandcanbeseentolargedistances

•  Massofredgiant=massofstarthanjustexhausteditshydrogen

•  ButmassdifficulttodeterminebasedonpositioninHRdiagram.

SDSS3‐‐APOGEE•  H‐bandsurveyofGalacticpopulations

•  100,000stars(80%redgiants)

•  R~25,000•  15elements–includingC,N,O,Na,Mg,Ca,Mn,Fe,Co,Ni

•  Targetedfrom2MASS

KeplerLightcurve

Huberetal.2010

WithMassandMetallicity–Age!

•  UsingscalingrelationsOKtofirstorder

•  Forbetteranalysis,comparemeasuredfrequencieswithpredictedfrequenciesfrommodels,includingcompositioninformation

•  Gaietal.2010Mosseretal.2011,Kallingeretal.2010,Metcalfeetal.2010

~150,000stars,~16,000giantsLongcadence–30min3.5yrmission

LookingAcrosstheGalaxy

AbundancesfromAPOGEE

•  TheAPOKASCcollaborationwillgetH‐bandspectrafor~10,000starsintheKeplerfield– 8,000redgiantsandredclumpstars– >1,000alreadyobserved– 1,000asteroseismicdwarfs

– 1,000dwarfswithrotationages•  Inaddition,~300CoRoTtargetswillbeobserved

AlongtheSolarCircle

GC

ThickDisk

SeismicAges‐‐complementary

•  AccuratedistancesfromGaiawillbeveryusefulforincreasingthenumberofstarswithwell‐measuredages

•  Agesaredeterminedfromthemasswhichisderivedfromtheseismicfrequencies

•  Measuringfrequenciesaccuratelydependsonbrightnessofstar,notdistance

•  Agesalsoindependentofreddening•  Differentsystematicdependenceonstellarmodels

Conclusions

•  RadialgradientflattenswithincreasingZ•  Verticalmetallicitygradient– Consistentwithtransitionfrom“thin”to“thick”disk

–  InconsistentwithGalacticmodelsthataretunedtomatchGCS

•  Understandingtheformationandevolutionofthediskrequiresaccurateages

•  Poisedtomakelargeadvancesinthisarea!