15.30 o10 p cottrell

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Research 7: P Cottrell

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  • 1.Globular Clusters: testing stellar evolution and nucleosynthesis theories Peter Cottrell Beatrice Tinsley Institute, Dept of Physics & Astronomy University of Canterbury, Christchurch, New Zealand & Max Planck Institute for Astrophysics, Garching, Germany(mid-May to mid-August)

2.

  • Science issues:
  • globular clusters (GC) : large samples of stars for testing stellar evolution and nucleosynthesis
  • what are the variations in some key nuclear products : C, N, Na,s - &r -process elements?
  • what stars are the origin of these elements?
  • Current and recent collaborators:
  • Clare Worley , Obs Cte dAzur, France;Jeffrey Simpson , Canterbury, NZ;
  • Iain McDonald , Manchester, UK;Jacco van Loon , Keele, UK;
  • Ken Freeman, Liz Wylie de Boer , ANU, Australia

3. 4. Colour Magnitude Diagram (CMD) : Stellar EvolutionMain Sequence:H-core burning First Giant Branch:H-shell burning Asymptotic Giant Branch:H- and He-shell burning Luminosity Temperature 5. Nuclear burning in stars

  • H- (p-p and CNO-cycle) and He-burning (3
  • n -capture reactions onto Fe seeds during late stages of evolution
    • r apid,s low compared to -decay
  • nsources [13 C( , n ) 16 O and22 Ne( , n ) 25 Mg ]
  • key products around magic peaks
    • s - : light ( Y, Sr, Zr ); heavy ( La, Ba, Nd );Pb
    • r -: ( Eu )
    • plus effects on other elements ( C, N, Na )

6. Abundance distribution of the nuclides lights- Pb heavys- & Eu (r-) 7. Karakas et al 2010 nproduced by22 Ne( , n ) 25 Mg nproduced by13 C( , n ) 16 O 8. Outline

  • large scale surveys of globular clusters
    • statistically significant samples
  • C, N, Na,s -process abundance results
    • Medium and high spectral resolution
    • AAT (Australia), SALT (South Africa), VLT (Chile)
  • SALT High Resolution Spectrograph (from 2012)

9. Large scale surveys of globular clusters VLT AAT SALT AAT High resolutionsingle object Medium resolution multi-object (MOS) Fabry P rot spectrophotometry Wavelength 10. VLT dataset : 47 Tuc, NGC 6388, NGC 362 & M15 11. Y ,Zr&Euabundances : fitting synthetic spectra (coloured lines) to the data ( ) 12. CN-weak/strong pairs with Na correlation 47 Tuc AAOmega data from AAT La IINd II 13. Na, CN correlation CMD : surface gravity (logg ) vs surface temperature (T eff ) increasing Naabundance increasing CNband strength Worley & Cottrell, 2011 14. Ba abundance variation in Cen (part of Jeffrey Simpsons PhD research) Fig 4 of Villanova et al 2010 Fig 7 of Stanford et al 2010 Fig 2 of Marino et al 2011 increasing Baabundance increasing Feabundance 15. R (= ) 2,000 of 1500 Cen stars van Loon et al 2007 16. R (= ) 2,000 of 1500 Cen stars 17. Spectrum synthesis grid + real spectrum 18. Statistical test for match van Loon et al 2007 19. Spectrum synthesis grid + real spectrum 20. [Ba/Fe] variations 21. C,N abundancesC normal, N enhanced by ~10 observations () fitted to synthetic spectrum (line) CH molecular lines CN lines 22. All CN, CH molecular lines removed from synthetic spectrum (line) CH molecular lines CN lines 23. 24. S outhernA fricanL argeT elescope(SALT) is an international consortium* that has built and is operating an 11m (91 hexagonal segment) telescope in South Africa * South African, Polish, German, USA, UK, Indian institutions and the University of Canterbury in New Zealand 25. 26. SALT image from 2010following recalibration of post-primary optics 8 arc minute field of view 27. What can SALT instruments do?

  • SALT Robert Stobie Spectrograph (RSS)
    • R (= ) up to 10,000
  • SALT High Resolution Spectrograph (HRS)
    • R from 16,000 to 65,000

Teff = 4500 K log g = 4.5 SALTRSS SALTHRS 47 Tuc CMD 28. SALT HRS : designed at Canterbury, constructed at Durham in UK 29. SALT HRS@ Durham April 2011 30. Summary

  • can use globular clusters to test stellar evolution theory & stellar nucleosynthesis yields (of C, N, Na &s-andr- process elements)
  • used high- & medium-resolution studies to infer abundances
  • -47 Tuc,Cen, but also NGC 6388, NGC 362, NGC 6752
  • plans to extend to other techniques on SALT (multi-object spectroscopy,Fabry-P rot interferometry, high-resolution spectroscopy) & to other galactic & extragalactic globular clusters