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Lecture 2 Abundances

Lecture 2 Abundances. Any study of nucleosynthesis must have one of its key objectives an accurate, physically motivated explanation for the pattern of abundances that we find in nature -- in the solar system (i.e., the sun) and in other locations in the cosmos

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Lecture 2 Abundances

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  1. Lecture 2 Abundances

  2. Any study of nucleosynthesis must have one of its key objectives an accurate, physically motivated explanation for the pattern of abundances that we find in nature -- in the solar system (i.e., the sun) and in other locations in the cosmos (other stars, the ISM, cosmic rays, IGM, and other galaxies) Key to that is accurate information on that pattern in the sun. For solar abundances there are three main sources: • The Earth - good for isotopic composition only • The solar spectrum • Meteorites, especially primitive ones

  3. The solar abundance distribution - should reflect the composition of the ISM when and where the sun was born Disk solar abundances: Elemental(and isotopic)compositionof Galaxy at location of solarsystem at the timeof it’s formation Halo + + Sun Bulge

  4. History: 1889, Frank W. Clarke read a paper before the PhilosophicalSociety of Washington “The Relative Abundance of the Chemical Elements” (current, not 1889) Current “abundance” distribution of elements in the earths crust:

  5. SOLAR ABUNDANCES normalized to 106 Si atoms CNO Fe

  6. The solar abundance pattern 256 “stable” isotopes 80 stable elements

  7. 1895 Rowland: relative intensities of 39 elemental signatures in solar spectrum 1929 Russell: calibrated solar spectral data to obtain table of abundances 1937 Goldschmidt: First analysis of “primordial” abundances: meteorites, sun 1956 Suess and Urey “Abundances of the Elements”, Rev. Mod. Phys. 28 (1956) 53 H. Schatz

  8. 1957 Burbidge, Burbidge, Fowler, Hoyle H. Schatz

  9. Since that time many surveys by e.g., Cameron (1970,1973) Anders and Ebihara (1982); Grevesse (1984) Anders and Grevesse (1989) - largely still in use Grevesse and Sauval (1998) Lodders (2003) Asplund, Grevesse and Sauval (2007) - assigned reading see class website

  10. H. Schatz Absorption Spectra: provide majority of data for elemental abundances because: • by far the largest number of elements can be observed • least fractionation as right at end of convection zone - still well mixed • well understood - good models available solar spectrum (Nigel Sharp, NOAO)

  11. Complications: • Oscillator strength: Needs to be measured in the laboratory - still not done with sufficient accuracyfor a number of elements. • Line width Depends on atomic properties but also thermal and turbulent broadening. Need an atmospheric model. • Ionization State

  12. H. Schatz Emission Spectra: Disadvantages: • less understood, more complicated solar regions (it is still not clear how exactly these layers are heated) • some fractionation/migration effects for example FIP: species with low first ionization potential are enhanced in respect to photosphere possibly because of fractionation between ions and neutral atoms Therefore abundances less accurate But there are elements that cannot be observed in the photosphere(for example helium is only seen in emission lines) this is how Heliumwas discovered bySir Joseph Lockyer ofEngland in 20 October 1868. Solar Chromospherered from Ha emissionlines

  13. H. Schatz Meteorites Meteorites can provide accurate information on elemental abundancesin the presolar nebula. More precise than solar spectra if data in some cases. Principal source for isotopic information. But some gases escape and cannot be determined this way (for example hydrogen, or noble gases) Not all meteorites are suitable - most of them are fractionatedand do not provide representative solar abundance information. One needs primitive meteorites that underwent little modification after forming. Classification of meteorites:

  14. H Schatz Use carbonaceous chondrites (~6% of falls) Chondrites: Have Chondrules - small ~1mm size shperical inclusions in matrix believed to have formed very early in the presolar nebula accreted together and remained largely unchanged since thenCarbonaceous Chondrites have lots of organic compounds that indicate very little heating (some were never heated above 50 degrees) Chondrule

  15. http://www.psrd.hawaii.edu/May06/meteoriteOrganics.html “Some carbonaceous chondrites smell. They contain volatile compounds that slowly give off chemicals with a distinctive organic aroma. Most types of carbonaceous chondrites (and there are lots of types) contain only about 2% organic compounds, but these are very important for understanding how organic compounds might have formed in the solar system. They even contain complex compounds such as amino acids, the building blocks of proteins.”

  16. AGS04 Lod03 Lod03 AG89 ZAMS* ZAMS* H 0.7392 0.7491 0.7110 0.7066 He 0.2486 0.2377 0.2741 0.2742 Z 0.0122 0.0133 0.0149 0.0191 * gravitational settling effects included He from Solar models Helioseismology Emission lines H II regions

  17. Grevesse andSauval (1998) quite similar to Anders and Grevesse (1989)

  18. Grevesse and Sauval, Spac. Sci. Rev., 85, 161, (1998) W Tb Differences between solar photospheric and meteoritic abundances in 1998. Most discrepancies were by then less than a factor of 30% but there were notable exceptions – Tb, In, W, Li..

  19. Bord and Cowley (Solar Physics, 211, 3 (2002)) Remaining discrepancies resolved for Ho, Lu, Tb as a consequence of better atomic physics for the spectral model. In and W remain problems. In especially a mystery. Is it volatility or atomic physics or both? W In

  20. Summary: (Lodders 2003) • 41 out of 56 rock forming elements, photospheric and meteoritic agree to within 15% • Relatively large disagreements still exist for elements with uncertain oscillator strengths - Au, Hf, In, Mn, Sn, Tm, W, and Yb - and for elements uncertain in meteorites - Cl, Ga, Rb • Most discrepant are W and In • X(4He) - protosolar - 0.2741 +- 0.012 • Li depleted in sun by factor of 150. Be and B not depleted in the sun • Ne and Ar are mainly from solar wind and flares and thus uncertain (< 0.2 dex). Ar has been seen in the solar spectrum. Kr and Xe abundances based in part on theory (n-capture cross sections)

  21. Major recent revisions: Lodders (2003) ApJ, 591, 1020 Asplund, Grevesse, and Sauval (2007) *Lower CNO abundances based upon the non-LTE 3D hydrodynamical modeling of the of the solar photosphere by Allende-Prieto et al (2001), ApJL, 556, L63 and (2002) ApJL, L137. All these papers are available on the class website!

  22. Lodders (2003)

  23. Asplund, Grevesse, and Sauval (2004)

  24. Grevesse, Asplund, and Sauval (Spac Sci Rev, 130, 105 (2007))

  25. Solar oxygen abundance based on log H = 12.0 Z O Anders and Grevesse (1989) 8.93 0.0189 Grevesse and Sauval (1995) 8.83 0.017 Grevesse, Asplund and Sauval (2007) 8.66 0.0122 (3D atmosphere; non-LTE Ni 6.23) Scott, Asplund, Grevesse and Sauval (2009) 8.71 (revised Ni abn 6.17) Many papers have noted that the large downwards revision of the solar metallicity gives a sound speed that is in discord with values inferred from solar oscillations. See Grevesse et al (2007) for a list.

  26. Grevesse, Asplund and Sauval (2007) choices for ZAMS solar Z and He Z = 0.0132 (now 0.0122) He = 0.2735

  27. CNO Fe Different processes of nucleosynthesis have their distinctive signature in the abundance distribution. r s p

  28. H. Schatz Abundances outside the solar neighborhood ? Abundances outside the solar system can be determined through: • Stellar absorption spectra of other stars than the sun • Interstellar absorption spectra • Emission lines, H II regions • Emission lines from Nebulae (Supernova remnants, Planetary nebulae, …) • g-ray detection from the decay of radioactive nuclei • Cosmic Rays • Presolar grains in meteorites

  29. E.g, metallicity gradient in Galactic disk: Hou et al. Chin. J. Astron. Astrophys. 2 (2002) 17 data from 89 open clusters radial iron gradient = -0.099 +_ 0.008 dex/kpc Many other works on this subject See e.g. Luck et al, 132, 902, AJ (2006) radial Fe gradient = - 0.068 +_ 0.003 dex/kpc from 54 Cepheids

  30. From Luck et al. Si S Ca Ti /Fe /H

  31. Y Y shows gradient Eu maybe Nd noisy La ? La Nd Eu /H /Fe

  32. Variation with metallicity Kobayashi et al, ApJ, 653, 1145, (2006)

  33. Kobayashi et al, ApJ, 653, 1145, (2006)

  34. CS 22892-052 Sneden et al, ApJ, 591, 936 (2003) [Fe/H] ~ -3.1

  35. Abundances in a damped Ly-alpha system at redshift 2.626. 20 elements. Metallicity ~ 1/3 solar Fenner, Prochaska, and Gibson, ApJ, 606, 116, (2004)

  36. Fenner et al (2004) vs WW95

  37. A&A, 416, 1117 Best fit, 0.9 B, = 1.35, mix = 0.0158, 10 - 100 solar masses Heger and Woosley 2007, in preparation) Data are for 35 giants with -4.1 < [Fe/H] < -2.7

  38. 28 metal poor stars in the Milky Way Galaxy -4 < [Fe/H] < -2; 13 are < -.26

  39. Frebel et al, ApJ, 638, 17, (2006) Aoki et al, ApJ, 639, 896, (2006)

  40. Christlieb et al 2007, in prepartion [Fe/H] = -5.1

  41. Abundances of cosmic rays arriving at Earth http://www.srl.caltech.edu/ACE/ Advanced Composition Explorer (1997 - 1998) time since acceleration about 107 yr. Note enhanced abundances of rare nuclei made by spallation

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