stellar abundance raos as populaon tracers€¦ · stellar abundance raos as populaon tracers 1....

Stellarabundancera-osaspopula-ontracers

1.  Basicinforma-on2.  Determina-onandtracerelements3.  Differencesingalac-cpopula-ons

1.  Galac-cDisk2.  Galac-cBulge3.  Galac-cHalo

Stellar abundance ratios as population tracers, Tina Neumann, 15.12.17

1.Basicsofmeasuringabundancera-os

•  receivedbyanalyzingspa-al&kinema-caldistribu-onfunc-onofstarsinspace,theirage&chemicalcomposi-on– MostlyF-/G-main-sequencestars&subgiants

(-3.0<[Fe/H]<0.4)•  Measuringmethods:

– Whenreliablecon-nuum:measuringequivalentwidths–  FiMngsynthe-cprofil– Uvby-β(Strömgren)-photometry


hTps://www.handprint.com/ASTRO/specclass.html Stellar abundance ratios as population tracers, Tina Neumann, 15.12.17

1.Basicsofmeasuringabundancera-os

•  receivedbyanalyzingspa-al&kinema-caldistribu-onfunc-onofstarsinspace,theirage&chemicalcomposi-on– MostlyF-/G-main-sequencestars&subgiants(-3.0<[Fe/H]<0.4)

•  Measuringmethods:

– Whenreliablecon-nuum:measuringequivalentwidths–  FiMngsynthe-cprofil–  uvby-β(Strömgren)-photometry


hTps://www.handprint.com/ASTRO/specclass.html Stellar abundance ratios as population tracers, Tina Neumann, 15.12.17

Determina-onofatmosphericparameters:•  Modelatmospheresassumed

–  ConsideringLTE(localthermodynamicequilibrium)Effec2vetemperature:determinedbycolour(nearstars)or

spectroscopy(moredistantstars)Gravity:determinedbyluminosityorspectroscopiallybyΔ[Fe/H]Inhomogeneous3D-modells:

•  Neededformorerealis-cvalues

–  Departures:couldcausechangesinabundance/metallicity


2.Determina-onandtracerelements

•  Equa-ontodeterminepopula-onofastar:

Popula)ontracerelements: •  C&O(byforbiddenlines) •  Intermediate-masselements

- Inconnec-onwithC-/O-/N-burningbytypeIISne - Fromaveragevaluemetallicityisdetermined

•  Ironelements • ObserveddifferencescouldgiveconstraintsonSnemodeling


n

P.E.Nissenetal.:Carbonandoxygenabundancesinstellarpopula-ons,2011

Pic.3/4:comparisonof[C/Fe]&[O/Fe]–[Fe/H]fordifferentgalac-cpopula-ons


Differentproper-esofsinglegalac-cparts

hTp://slideplayer.com/slide/5189502/ Stellar abundance ratios as population tracers, Tina Neumann, 15.12.17

3.1Galac-cDisk

Thin-disk•  Height:300pc•  Age:about9Gyr

Thick-disk •  Height:1.300pc •  Age:about13Gyr

Overlappingregion: •  At-0.6<[Fe/H]<-0.3 •  Onlyfewtransi-onstars •  Seemtobeconnectedtobothtypes

Gapbetweenthistwodiskcomponents: •  At[Fe/H]<0.1 •  Suggestedsystema-cdifferenceof[Mg/Fe]connectedtogapinstarforma-onbetweenboth


ChemicalAbundancesasPopula-onTracers,PoulErikNissen,2013

Kinema-c/metallicityproper-esofdiskstars


Fig.5:[α/Fe]asafunc-onof[Fe/H]StarswithorbitsRm<7kpc(filledcircles);stars(opencircles)with7<Rm<9kpc;stars(crosses)withRm>9kpc

Fig.6:Toomre-energydiagrammofstars



Scenariosofdiskdevelopment

•  Atfirstperiodofrapidstarforma-on–  Interruptedbymergingsatellitegalaxies

•  Alreadyfromedstarsheatedtothick-diskkinema-cs•  Hiatusinstarforma-on(metal-poorgaswasaccreted)-->firstthin-diskstarswereformedModelofchemicalevolu-onofgalac-cdisk:

•  Starforma-ondecreasesmonotonically,includingradialmigra-on&gasflows

•  predictsbimodaldistribu-onof[α/Fe]


3.2Galac-cbulge

2classicalforma-onscenarios:•  Coalescenceofstar-formingclumps•  Developmentof`pseudobulge`overlong-methroughdynamicaldiskinstabili-es

Pic.8:viewofmilkywaybulge

2tendenciesofregionsinthegalac2cplane:1.  metal-poorregion:

•  Behavelikethick-diskstars•  Averageage:11.2Gyr

2.metal-richgroup•  Similiarproper-estothin-diskstars•  Averageage:7.6Gyr

–  Thisassymetricdistribu-onwasalsoderivedbycomparingthisstarsbygravity-Teff

Pic.9:visuliza-onofthe[α/Fe]/[Fe/H]forKbulgestarscomparedtostarswiththick-disk&thin-diskkinema-cs



3.3Galac-chalo

•  Separa-onofhalopopula-ons:I.  popula-on:

•  Inner,older,flaTened •  Prograderota-ng(more

boundtogalaxy) •  Formedduring

dissipa-vecollapse •  Inhighrate

chemicalevolu-onregions(bySneII)

•  [Fe/H]=-1.6 •  Specialthat[Mg/Fe]

constant

II.popula-on: •  Outer,younger,

spherical •  2/3retrograderota-ng

(lessboundtogalaxy) •  Accretedbysatellite

galaxies •  Inslowrate

chemicalevolu-onregions(bySneIa)

•  [Fe/H]=-2.2 •  Declining[Mg/Fe]

Pic.10:[Mg/Fe]&[α/Fe]vs.[Fe/H]halostarsdevidedinlow-α(filledredcircles)&high-α(openbluecircles) ChemicalAbundancesasPopula-onTracers,PoulErik

Nissen,2013 Stellar abundance ratios as population tracers, Tina Neumann, 15.12.17

Summariza-on

•  Therewereactuallyalotofunexpectedproper-esfound

•  Thereexistsubclassestonormalpopula-onI/IIInfuture:•  Moredataneeded•  BeTerunderstandingof3D-/non-LTEeffects,nucleosynthesis

•  Seperatediferentspectralandluminosi-esclasses,dwarfs-giants


[α/Fe]vs.[Fe/H]forvariousstellarpopula)ons{Thin-diskstars:plussymbols;thick-diskstars:filledcircles;microlensedbulgestars:filledredsquares;high-α:openbluecirclesandlow-αhalostars:filledredcircles;starsintheSculptordSphgalaxy:filledgreentrianglesandstarsfromSagitariusgalaxy:stars}


ReferencesSource:•  T.D.Oswalt,G.Gilmore(eds.),Planets,StarsandStellarSystems.

Volume5:Galac-cStructureandStellarPopula-ons,2013•  P.E.Nissen,ChemicalAbundancesasPopula-onTracers,2013•  P.E.Nissenetal.:Carbonandoxygenabundancesinstellar

popula-ons2011•  hTp://icc.dur.ac.uk/~T/Lectures/Galaxies/TeX/lec/node27.htmlPictures:•  hTps://www.handprint.com/ASTRO/specclass.html•  hTp://slideplayer.com/slide/5189502/•  hTps://www.planet-wissen.de/technik/weltraumforschung/

astronomie/pwieunsereheimatgalaxiediemilchstrasse100.html


stellar abundance raos as populaon tracers€¦ · stellar abundance raos as populaon tracers 1....

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