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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 358660.0, MPI für Astronomie / Publikationen_mpia
Dust in the wnd: crystalline silicates, corundum, and periclase in PG 2112+059
Authors:Markwick-Kemper, F.; Gallagher, S. C.; Hines, D. C.; Bouwman, J.
Date of Publication (YYYY-MM-DD):2007
Title of Journal:The Astrophysical Journal
Start Page:L107
End Page:L110
Audience:Not Specified
Abstract / Description:We have determined the mineralogical composition of dust in the broad absorption line (BAL) quasar PG 2112+059 using mid-infrared spectroscopy obtained with the Spitzer Space Telescope. From spectral fitting of the solid state features, we find evidence for Mg-rich amorphous silicates with olivine stoichiometry, as well as the first detection of corundum (Al 2O3) and periclase (MgO) in quasars. This mixed composition provides the first direct evidence for a clumpy density structure of the grain-forming region. The silicates in total encompass 56.5% +/- 1.4% of the identified dust mass, while corundum takes up 38+/-3 wt.%. Depending on the choice of continuum, a range of mass fractions is observed for periclase ranging from 2.7% +/- 1.7% in the most conservative case to 9% +/- 2% in a less-constrained continuum. In addition, we identify a feature at 11.2 mum as the crystalline silicate forsterite, with only a minor contribution from polycyclic aromatic hydrocarbons. The 5% +/- 3% crystalline silicate fraction requires high temperatures such as those found in the immediate quasar environment in order to counteract rapid destruction from cosmic rays.
Free Keywords:ISM: Dust; Extinction; Galaxies: Active; Galaxies: Quasars: Emission Lines; Galaxies: Quasars: Individual: Alphanumeric: PG 2112+059
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
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