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The (Un)True Deuterium Abundance in the Galactic Disk

?. Tijana Prodanović, University of Novi Sad Gary Steigman , Ohio State University Brian D. Fields, University of Illinois at Urbana Champaign. The (Un)True Deuterium Abundance in the Galactic Disk. Only created in Big Bang ( Boesgaard & Steigman 1985)

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The (Un)True Deuterium Abundance in the Galactic Disk

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  1. IAU Symposium 268: Light Elements in the Universe November 9th 2009 ? Tijana Prodanović, University of Novi Sad Gary Steigman, Ohio State University Brian D. Fields, University of Illinois at Urbana Champaign The (Un)True Deuterium Abundance in the Galactic Disk

  2. Only created in Big Bang (Boesgaard & Steigman 1985) • All other processes destroy it (Epstein et al. 1976, Prodanović & Fields 2003) • Should (?) decrease monotonically from high to low z • Deuterium – a powerful tool in cosmology! • Cosmic baryometer! BBN success story • WMAP & BBN (blue) and high-z obs. (yellow) – a match! • Deuterium – a powerful tool in chemical evolution! • Probes virgin ISM fraction! IAU Symposium 268: Light Elements in the Universe, November 9th 2009 STORY ABOUt DEUTERIUM Cyburt et al. (2008)

  3. Large variations of D in local ISM over different lines of sight! IAU Symposium 268: Light Elements in the Universe, November 9th 2009 The TroublE Data from Linsky at al. (2006)

  4. Deuterium preferentially (compared to H) depleted onto dust! (Jura 1982, Draine 2004, 2006) • Measure lower bound on the “true” D • “True” ISM D abundance (Linsky at al. 2006) • “True” ISM D = 82% of PRIMORDIAL! IAU Symposium 268: Light Elements in the Universe, November 9th 2009 SOLUTION?

  5. Deuterium destroyed through stellar cycling • Astration factor (Steigman et al. 2007) • But new FUSE high ISM D • Most gas still unprocessed? • Gas observations say ~20% of present baryonic mass in ISM • But D observations say ~80% initial gas unprocessed! • Thus GCE says INFALL NEEDED IAU Symposium 268: Light Elements in the Universe November 9th 2009 Galactic chemical evolutuon

  6. Assume infall rate ~ star form. rate • D vs. gas fraction • Shaded = observations • Allowed infall rate • Almost balances out star-formation! • Still tension with GCE • Is ISM D really so high? Prodanovic & Fields 2008 IAU Symposium 268: Light Elements in the Universe, November 9th 2009 How much infall? Linsky et al. 2006

  7. Try something different – make (almost) no assumptions • Bayesian analysis (introduced by Hogan et al. 1997) • Use all available LOS • Assume only a possible (dust) depletion • Find 2-parameter maximum likelihood • - Max. D abundance consistent withobservations; a lower limit to true ISM D • - Depletion parameter IAU Symposium 268: Light Elements in the Universe November 9th 2009 A BAYESIAN approach Prodanovic, Steigman & Fields (2009) arXiv:0910.4961

  8. Know nothing about (dust) depletion distribution • Make as little assumptions • Top hat – all levels of depletion equally probable • Negative bias – favors large depletion • Positive bias – favors low depletion IAU Symposium 268: Light Elements in the Universe November 9th 2009 Choice: Depletion distributions

  9. Local Bubble very different from non-Local Bubble • LB – blue • Uniform • nLB – red • Large scatter • First treat separately IAU Symposium 268: Light Elements in the Universe November 9th 2009 LB vs. Non-LB Prodanovic, Steigman & Fields (2009) arXiv:0910.4961

  10. IAU Symposium 268: Light Elements in the Universe November 9th 2009 • Top-hat depletion distribution • 21 Local Bubble LOS • 25 non-Local Bubble LOS • All 46 LOS Results: Likelihood contours Prodanovic, Steigman & Fields (2009) arXiv:0910.4961

  11. Use all 46 LOS Top-hat depletion distribution – highest max likelihood value Marginally consistent with Releases tension with GCE models IAU Symposium 268: Light Elements in the Universe November 9th 2009 Results: true ism d abundance Linsky et al. (2006)

  12. If Local ISM D abundance close to primordial – problems with most GCE models • Bayesian analysis following Hogan et al. (1997) • Assume all variations due to (dust) depletion • Analyze all LOS • Tested 3 simple depletion distributions • Top-hat gives max likelihood value • “True” ISM D abundance new estimate: IAU Symposium 268: Light Elements in the Universe, November 9th 2009 Summary & conclusions Prodanovic, Steigman & Fields (2009) arXiv:0910.4961

  13. Uniform LB D abundance vs. large scatter in nLB? • LB - no depletion? • nLB – large depletion? • Is LB uniformily depleted? • Is nLB enriched with unmixed infall? • How do we discriminate? • Is Fe really a good depletion indicator for D? • Steigman & Prodanović (2009/10) in preparation IAU Symposium 268: Light Elements in the Universe November 9th 2009 problems

  14. IAU Symposium 268: Light Elements in the Universe, November 9th 2009 Thank You!

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