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)