15.30 o10 p cottrell

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Research 7: P Cottrell

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15.30 o10 p cottrell

  1. 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. 2. <ul><li>Science issues: </li></ul><ul><li>globular clusters (GC) : large samples of stars for testing stellar evolution and nucleosynthesis </li></ul><ul><li>what are the variations in some key nuclear products : C, N, Na, s - & r -process elements? </li></ul><ul><li>what stars are the origin of these elements? </li></ul><ul><li>Current and recent collaborators: </li></ul><ul><li>Clare Worley , Obs Côte d’Azur, France; Jeffrey Simpson , Canterbury, NZ; </li></ul><ul><li>Iain McDonald , Manchester, UK; Jacco van Loon , Keele, UK; </li></ul><ul><li>Ken Freeman, Liz Wylie de Boer , ANU, Australia </li></ul>
  3. 4. Colour Magnitude Diagram (CMD) : Stellar Evolution Main Sequence: H-core burning First Giant Branch: H-shell burning Asymptotic Giant Branch: H- and He-shell burning Luminosity   Temperature
  4. 5. Nuclear burning in stars <ul><li>H- (p-p and CNO-cycle) and He-burning (3  </li></ul><ul><li>n -capture reactions onto Fe “seeds” during late stages of evolution </li></ul><ul><ul><li>r apid, s low compared to  -decay </li></ul></ul><ul><li>n sources [ 13 C(  , n ) 16 O and 22 Ne(  , n ) 25 Mg ] </li></ul><ul><li>key products around magic peaks </li></ul><ul><ul><li>s - : light ( Y, Sr, Zr ); heavy ( La, Ba, Nd ); Pb </li></ul></ul><ul><ul><li>r - : ( Eu ) </li></ul></ul><ul><ul><li>plus effects on other elements ( C, N, Na ) </li></ul></ul>
  5. 6. Abundance distribution of the nuclides light s- Pb heavy s- & Eu (r-)
  6. 7. Karakas et al 2010 n produced by 22 Ne(  , n ) 25 Mg n produced by 13 C(  , n ) 16 O
  7. 8. Outline <ul><li>large scale surveys of globular clusters </li></ul><ul><ul><li>statistically significant samples </li></ul></ul><ul><li>C, N, Na, s -process abundance results </li></ul><ul><ul><li>Medium and high spectral resolution </li></ul></ul><ul><ul><li>AAT (Australia), SALT (South Africa), VLT (Chile) </li></ul></ul><ul><li>SALT High Resolution Spectrograph (from 2012) </li></ul>
  8. 9. Large scale surveys of globular clusters VLT AAT SALT AAT High resolution single object Medium resolution multi-object (MOS) Fabry – P é rot spectrophotometry Wavelength
  9. 10. VLT dataset : 47 Tuc, NGC 6388, NGC 362 & M15
  10. 11. Y , Zr & Eu abundances : fitting synthetic spectra (coloured lines) to the data ( ••• )
  11. 12. CN-weak/strong pairs with Na correlation 47 Tuc AAOmega data from AAT La II Nd II
  12. 13. Na, CN correlation CMD : surface gravity (log g ) vs surface temperature (T eff ) increasing Na abundance increasing CN band strength Worley & Cottrell, 2011
  13. 14. Ba abundance variation in  Cen (part of Jeffrey Simpson’s PhD research) Fig 4 of Villanova et al 2010 Fig 7 of Stanford et al 2010 Fig 2 of Marino et al 2011 increasing Ba abundance increasing Fe abundance
  14. 15. R (=  ) 2,000 of 1500  Cen stars van Loon et al 2007
  15. 16. R (=  ) 2,000 of 1500  Cen stars
  16. 17. Spectrum synthesis grid + real spectrum
  17. 18. Statistical test for match van Loon et al 2007
  18. 19. Spectrum synthesis grid + real spectrum
  19. 20. [Ba/Fe] variations
  20. 21. C,N abundances C normal, N enhanced by ~10 observations (•••) fitted to synthetic spectrum (line) CH molecular lines CN lines
  21. 22. All CN, CH molecular lines removed from synthetic spectrum (line) CH molecular lines CN lines
  22. 24. S outhern A frican L arge T 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
  23. 26. SALT image from 2010 following recalibration of post-primary optics 8 arc minute field of view
  24. 27. What can SALT instruments do? <ul><li>SALT Robert Stobie Spectrograph (RSS) </li></ul><ul><ul><li>R (=  ) up to 10,000 </li></ul></ul><ul><li>SALT High Resolution Spectrograph (HRS) </li></ul><ul><ul><li>R from 16,000 to 65,000 </li></ul></ul>Teff = 4500 K log g = 4.5 SALT RSS SALT HRS 47 Tuc CMD
  25. 28. SALT HRS : designed at Canterbury, constructed at Durham in UK
  26. 29. SALT HRS @ Durham April 2011
  27. 30. Summary <ul><li>can use globular clusters to test stellar evolution theory & stellar nucleosynthesis yields (of C, N, Na & s- and r- process elements) </li></ul><ul><li>used high- & medium-resolution studies to infer abundances </li></ul><ul><li>- 47 Tuc,  Cen, but also NGC 6388, NGC 362, NGC 6752 </li></ul><ul><li>plans to extend to other techniques on SALT (multi-object spectroscopy, Fabry-P érot interferometry, high-resolution spectroscopy) & to other galactic & extragalactic globular clusters </li></ul>

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