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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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slide1

Fe II Emission in AGN:

The Role of Fe Abundance

Gregory Shields , Randi Ludwig, SarahSalviander( arXiv:1006:2043)

slide2

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.
slide3

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.
slide4

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.
slide7

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.
slide9

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.
slide10

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.
slide12

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

slide13

Keck AO Images of Type 1 Binary Candidates

C. Max et al. 2010 in progress