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Blue Channel spectroscopy of quasar absorption lines: Metal abundances and dust in DLYAs

Blue Channel spectroscopy of quasar absorption lines: Metal abundances and dust in DLYAs. Jill Bechtold, Jun Cui (Steward Observatory) Varsha Kulkarni, Joe Meiring, Pushpa Khare (Univ. S. Carolina) Don York (Chicago) James Lauroesch (Northwestern) And others 2004 ApJ 616, 86

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Blue Channel spectroscopy of quasar absorption lines: Metal abundances and dust in DLYAs

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  1. Blue Channel spectroscopy ofquasar absorption lines:Metal abundances and dust in DLYAs Jill Bechtold, Jun Cui (Steward Observatory) Varsha Kulkarni, Joe Meiring, Pushpa Khare (Univ. S. Carolina) Don York (Chicago) James Lauroesch (Northwestern) And others 2004 ApJ 616, 86 2005 ApJ 618, 68 2006 In press, astro-ph/0604617 NOAO public access & UA allocations

  2. Background for non-astronomers

  3. For z<1.6 (corresponding to 70% age of the Universe) Lyman alpha observed with HST; interesting lines of metals in blue from ground

  4. Use DLYAs to observe relative abundances of the elements in the interstellar gas clouds of distant galaxies as a function of cosmic time each generation of stars  supernovae, planetary nebula winds  more “heavy elements”

  5. Complication: Atoms of abundant elements freeze out onto dust grains Iron: Variable “depletion” depending on when the last supernova blast passed through

  6. Solution: Look for ZINC Doesn’t freeze out onto dust grains Zinc and Iron have similar nucleosynthetic histories In same spectra region: typically see lines from Chromium Chromium is heavily depleted, so strength tells you about dust Zn/H versus z (or equivalently look-back time)  evolution of metallicity Ground-based: Z>1.6 ~ hundred DLYAs measured Before SDSS: QSO Absorption line Key Project had ONE z<1.6 DLYA

  7. Experiment: Use SDSS quasar spectra to find very strong Mg II absorbers, with strong Mg I Follow-up with HST to look for characteristic damped Lyman alpha line (Rao+, Becker+, Kulkarni+, Bechtold+ HST programs) Measure Zinc, chromium, iron absorption lines with MMT Spectra

  8. MMT Blue Spectrograph832 l/mm 2nd order

  9. Solar 1/10 Solar 1/100 solar Lookback 7.7 10.3 11.5 12.1 time (billion years)

  10. Expect low redshift damped Ly alpha absorbers to be more metal rich • Probably due to selection effect: high Zn/H systems missing more metals  more dust, background quasar dimmed

  11. New Sample for follow-up studies Chandra X-ray Spectroscopy of absorption: • Soft X-ray absorption due to oxygen • Zn/H  iron peak elements • Pop II Stars: (old stars in Milky Way) have enhanced oxygen WRT iron peak, due to massive star supernovae early on • MAESTRO spectroscopy • detect Zn, Cr, other trace elements • history of nucleosynthesis

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