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Fe II Emission in AGN: The Role of Fe Abundance

Fe II Emission in AGN: The Role of Fe Abundance. Gregory Shields , Randi Ludwig, S arah Salviander ( arXiv:1006:2043). Abstract. Optical Fe II emission from BLR varies widely among AGN.

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Fe II Emission in AGN: The Role of Fe Abundance

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  1. Fe II Emission in AGN: The Role of Fe Abundance Gregory Shields , Randi Ludwig, SarahSalviander( arXiv:1006:2043)

  2. Abstract • Optical Fe II emission from BLR varies widely among AGN. • Composite spectra from SDSS grouped by Fe II strength allow measurement of weak narrow lines. Results rule out Fe/alpha and Fe/H as major cause of Fe II range. • Empirical correlations and photo-ionization models rule out X-ray strength as major cause. • Depletion of Fe into grains in outer BLR may be largely responsible.

  3. Intro • AGN show strong broad Fe II emission bands in optical and UV • Optical Fe II shows range 1.5 dex or more, UV somewhat less • Photoionization models have some success explaining Fe II emission but strongest Fe II is problematic. • Wide range of optical Fe II not understood. • Interest in Fe abundance in QSOs for early galactic chemical evolution.

  4. Iron Abundance • Photoionization models need enhanced Fe abundance to explain strongest Fe II objects. • Abundances in broad line region (BLR) are hard to measure. • Narrow line region (NLR) is easier. • [Fe VII]/[Ne V] good measure of Fe/Ne ratio (Nussbaumer & Osterbrock 1970) • Created composite SDSS spectra binned by Fe II/Hbeta to bring out weak • [Fe VII] line. • Results show insignificant trend in Fe/Ne with Fe II strength • Modest trend in [N II]/[S II] with Fe II strength suggests overall metallicity makes small contribution to range of Fe II strength.

  5. Fe VII and Ne V

  6. Trends with Fe II Strength

  7. Fe Depletion into Grains? • Fe/H down 1 -2 dex in ISM, planetary nebulae, H II regions. Depletions of other refractory elements vary. • Strong Fe II objects cannot have such depletions of Mg, Si, Fe (Gaskell, Shields, Wampler 1981) • Suggest that Fe depletion varies among AGN. • Dust sublimation may determine BLR radius (Netzer & Laor 1993). Indications of inflow from “dusty torus” to BLR; Fe II emission from outer BLR. • Photoionization models show optical Fe II linear in abundances, UV Fe II weaker dependence. • Raises questions about BLR relation to accretion flow, dust destruction processes, depletions of different refractory elements, BH masses.

  8. Abstract • Optical Fe II emission from BLR varies widely among AGN. • Composite spectra from SDSS grouped by Fe II strength allow measurement of weak narrow lines. Results rule out Fe/alpha and Fe/H as major cause of Fe II range. • Empirical correlations and photo-ionization models rule out X-ray strength as major cause. • Depletion of Fe into grains in outer BLR may be largely responsible.

  9. Abstract • Optical Fe II emission from BLR varies widely among AGN. • Composite spectra from SDSS grouped by Fe II strength allow measurement of weak narrow lines. Results rule out Fe/alpha and Fe/H as major cause of Fe II range. • Empirical correlations and photo-ionization models rule out X-ray strength as major cause. • Depletion of Fe into grains in outer BLR may be largely responsible.

  10. Radio Jet Interaction • Radio jets can affect the dynamics of the NLR and create double-peaked [OIII]. • J1517+33 (Rosario et al. 2010) • While 27% of our broad-line objects exhibit FIRST (limit 1 mJy) radio detection, it should be noted that an absence of detection does not necessarily mean there are no jets. VLA image of J1517+33

  11. Keck AO Images of Type 1 Binary Candidates C. Max et al. 2010 in progress

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