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
Stellar abundance ratios as population tracers, Tina Neumann, 15.12.17
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
Stellar abundance ratios as population tracers, Tina Neumann, 15.12.17
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
Stellar abundance ratios as population tracers, Tina Neumann, 15.12.17
2.Determina-onandtracerelements
• Equa-ontodeterminepopula-onofastar:
Popula)ontracerelements: • C&O(byforbiddenlines) • Intermediate-masselements
- Inconnec-onwithC-/O-/N-burningbytypeIISne - Fromaveragevaluemetallicityisdetermined
• Ironelements • ObserveddifferencescouldgiveconstraintsonSnemodeling
Stellar abundance ratios as population tracers, Tina Neumann, 15.12.17
n
P.E.Nissenetal.:Carbonandoxygenabundancesinstellarpopula-ons,2011
Pic.3/4:comparisonof[C/Fe]&[O/Fe]–[Fe/H]fordifferentgalac-cpopula-ons
Stellar abundance ratios as population tracers, Tina Neumann, 15.12.17
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
Stellar abundance ratios as population tracers, Tina Neumann, 15.12.17
ChemicalAbundancesasPopula-onTracers,PoulErikNissen,2013
Kinema-c/metallicityproper-esofdiskstars
Stellar abundance ratios as population tracers, Tina Neumann, 15.12.17
Fig.5:[α/Fe]asafunc-onof[Fe/H]StarswithorbitsRm<7kpc(filledcircles);stars(opencircles)with7<Rm<9kpc;stars(crosses)withRm>9kpc
Fig.6:Toomre-energydiagrammofstars
ChemicalAbundancesasPopula-onTracers,PoulErikNissen,2013
Stellar abundance ratios as population tracers, Tina Neumann, 15.12.17
Scenariosofdiskdevelopment
• Atfirstperiodofrapidstarforma-on– Interruptedbymergingsatellitegalaxies
• Alreadyfromedstarsheatedtothick-diskkinema-cs• Hiatusinstarforma-on(metal-poorgaswasaccreted)-->firstthin-diskstarswereformedModelofchemicalevolu-onofgalac-cdisk:
• Starforma-ondecreasesmonotonically,includingradialmigra-on&gasflows
• predictsbimodaldistribu-onof[α/Fe]
Stellar abundance ratios as population tracers, Tina Neumann, 15.12.17
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
ChemicalAbundancesasPopula-onTracers,PoulErikNissen,2013
Stellar abundance ratios as population tracers, Tina Neumann, 15.12.17
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
ChemicalAbundancesasPopula-onTracers,PoulErikNissen,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
Stellar abundance ratios as population tracers, Tina Neumann, 15.12.17
[α/Fe]vs.[Fe/H]forvariousstellarpopula)ons{Thin-diskstars:plussymbols;thick-diskstars:filledcircles;microlensedbulgestars:filledredsquares;high-α:openbluecirclesandlow-αhalostars:filledredcircles;starsintheSculptordSphgalaxy:filledgreentrianglesandstarsfromSagitariusgalaxy:stars}
Stellar abundance ratios as population tracers, Tina Neumann, 15.12.17
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 ratios as population tracers, Tina Neumann, 15.12.17