StellarAbundances

MariaBergemann ResearchGroup“StellarSpectroscopyandStellarPopulations”

Max-PlanckInstituteforAstronomy,Heidelberg

Outline

• Motivation• Abundancemeasurementsincoolstars• Chemicalevolutionmodels:• successes• unknowns

• Conclusions

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MotivationLatetypestars:allstellarpopulaLons-6<[Fe/H]<+0.530-50elements:He,Li…,UseveralionizaLonstagesSunasareference

HugeobservaLonaldatasets:largestellarsurveysSEGUE,Gaia-ESO,APOGEE,Galah,total~2millionspectra

4MOST(*2021):+20millionspectra

New:extragalacLcspectroscopyofindividualstars,andstarclustersoutto70Mpc(Evansetal.2011)

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Newtechniques

Tingetal.2016,Rixetal.2016,Tingetal.inprep

Betterstatisticalmodelstodeterminestellarabundancesmaysoonyieldwaymoreinformationonrare-earths

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Newmodelsrecently,mosteffortsfocuson3D,NLTE✓ 3Dconvectionsimulations✓ Non-localthermodynamicequilibrium

∂ni∂t

+∂(ni υ)∂z

= njj≠i

N

∑ Pji −ni Pijj≠i

N

∑Bergemann+2012a,b,c,2013;Magic+2014,Collet+2012,Lind+

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H He

Li Be B C N O F

Na Mg Al Si P S

K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn

Rb Sr Y Zr Pd

Cs Ba Lu Hf Os Ir Pt Au Pb

La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb

State-of-the-art

3DNon-LTE1DNon-LTE1DLTE

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AbundancesinGalacticstars[Na/Fe]

NLTE

LTE

Lindetal.(2011),Jacobsonetal.(2015)

[O/Fe]

Amarsietal.(2015)

NLTE3D

[Mn/Fe]

[Co/Fe]

Battistini&Bensby(2015)

[Ba/Fe] [Eu/Fe]

Mashonkinaetal.(2003)

Hansenetal.(2013)

[Sr/Fe]

[Cu/Fe]

NLTE

Yanetal.(2016)

Mashonkinaetal.(2003)

NLTE

10Matteucci&Brocato(1990)

• initialconditions• stellarbirthratefunction• stellaryields• gasflows(infall,outflow,

radialflow)

ChemicalEvolutionmodelsfortheMilkyWay

11Andrewsetal.(2016)

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thecombineduncertainty:theslopeandmasslimitsoftheIMF,thenumberanddelaytimedistributionofSNIa,thepresent-daymassingasandinstars

[O/Fe]

Côtéetal.2016

[Fe/H]

13Côtéetal.2016

varyingotherparametersinthechemicalevolutionmodels

Majordisagreementforthemostchemicalelementsmeasuredincool starssuggestthecurrentnucleosyntheissyieldsareincomplete.

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Successes• Magnesium

Bergemannetal.(2016b,subm.)

[Mg/Fe]

[Fe/H]

-1 0-2

• Copper

[Fe/H]

-1 0-2

[Cu/Fe]

Yanetal.(2016)

NLTE

NLTE

Manganese• observationallychallenging:hyperfinesplitting

• strongnon-localthermodynamicequilibriumeffects

• butexcellentobservationaldatabases

• consistencycheckfortheSNIaDTD?• SNIIunderproduceMnIatallmetallicityWW95:Z-dependentyields

• Chandrasekhar-massSNIamodels(Finketal.2014):enhanced[Mn/Fe]~0.3dex

• Sub-Chandrasekhar-massSNIamodels(Woosley&Kasen2011,Seitenzahletal.2013):deficient[Mn/Fe]butincreaseswith[Fe/H]

Seitenzahletal.(2013)

near-Ch

sub-Ch

Manganese

• NLTE[Mn/Fe]trendisflat atthesolarvalueforallmetallicities

• NLTEabundancesinverymetal-poorstars(Jacobson&Frebel2016)confirmsolar[Mn/Fe]andstrongdifferentalNLTEeffect

• isconsistentwithsub-Chmodels,andtheSNIatime-delay—>SNIIyieldsareinquestion

Battistini&Bensby(2015)

Jacobson&Frebel(2016)

Cobalt

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Battistini&Bensby(2015)

Jacobson&Frebel(2016)

Chromium

Bonifacioetal.(2012)

Bensbyetal.(2014)

Themainchallengesandquestions• N,Na,Mg,K,Ti,V,NiandZnarenotproducedin

quantitiesappropriatetothesolarabundanceinanyCCSNandSNIamodel(offsets0.2to0.5dex)

• Chemicalevolutionmodelsdonotdescribetheobservedabundanceratiosformostchemicalelements:• mainproblemsforelementsproducedinexplosion

(K,Sc,Ti,V,Mn,Co,Ni);alsoC,N• low-[Z]:needforanadditionalnuclesynthesis

channel?Na,Al,Zn• Thenextmajorstep:elementswithsimilar

nucleosyntheticorigin(Fe-peak—Ti,Mn,Co,Ni)