Pixie Dust: The Silicate Features in the Diffuse Interstellar Medium

By J. Chiar, A. Tielens. 2005

228 citations recorded by the source corpus.

We have analyzed the 9.7 and "18" μm interstellar silicate absorption features along the line of sight toward four heavily extincted galactic WC-type Wolf-Rayet (WR) stars. We construct two interstellar extinction curves from 1.25 to 25 μm using near-IR extinction measurements from the literature, along with the silicate profiles of WR 98a (representing the local ISM) and GCS 3 (representing the Galactic center). We have investigated the mineralogy of the interstellar silicates by comparing extinction profiles for amorphous silicates with olivine and pyroxene stoichiometry to the 9.7 and "18" μm absorption features in the WR 98a spectrum. In this analysis, we have considered solid and porous spheres and a continuous distribution of ellipsoids. While it is not possible to simultaneously provide a perfect match to both profiles, we find that the best match requires a mixture of these two types of compounds. We also consider iron oxides, aluminosilicates, and silicate carbide (SiC) as grain components. Iron oxides cannot be accommodated in the observed spectrum, while the amount of Si in SiC is limited to <4%. Finally, we discuss the cosmic elemental abundance constraints on the silicate mineralogy, grain shape, and porosity.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/d8e431d603d3f3f05e2bf165605367231f8b9c99

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Citations in the corpus

A Spitzer IRS Low-Resolution Spectroscopic Search for Buried AGNs in Nearby Ultraluminous Infrared Galaxies: A Constraint on Geometry between Energy Sources and Dust (2007, background): “However, the 18 m silicate profile of the Galactic, highly obscured star GCS3-I extends far beyond krest 24 m and reaches to krest 29 m (Chiar & Tielens 2006; see also Fig.”
SPITZER QUASAR AND ULIRG EVOLUTION STUDY (QUEST). IV. COMPARISON OF 1 Jy ULTRALUMINOUS INFRARED GALAXIES WITH PALOMAR-GREEN QUASARS (2009, methodology): “A modified version of the Chiar & Tielens (2006) Galactic Center extinction curve was used.”
Evolution of interstellar dust and stardust in the solar neighbourhood (2007, background): “However, metallic iron is probably unstable against oxidation in the ISM (Jones 1990), while, on the other hand, iron oxides do not seem to form a signiﬁcant species in the ISM dust mixture (Chiar & Tielens 2006).”
TORUS AND ACTIVE GALACTIC NUCLEUS PROPERTIES OF NEARBY SEYFERT GALAXIES: RESULTS FROM FITTING INFRARED SPECTRAL ENERGY DISTRIBUTIONS AND SPECTROSCOPY (2011, methodology): “We use the IR extinction curve of Chiar & Tielens (2006) of the local ISM in the wavelength range ∼ 1 − 35µm, which includes the two silicate features at 9.7 and 18µm.”
Towards a complete census of AGN in nearby Galaxies: a large population of optically unidentified AGN (2009, unknown): “32 ∼ 1.03 (Chiar & Tielens 2006).”
The Mid-Infrared Spectrum of Star-forming Galaxies: Global Properties of Polycyclic Aromatic Hydrocarbon Emission (2006, methodology): “We also explored using the Galactic center extinction curve of Chiar & Tielens (2006), with similar values of τ9.”
High-Resolution Mid-Infrared Spectroscopy of Ultraluminous Infrared Galaxies (2007, background): “The ionized gas gives rise to the finestructure lines, while the smaller dust grains produce the mid-IR continuum longward of about 10 m. Larger dust grains give rise to features such as the absorption features at 9.7 and 18 m (Lebofsky&Rieke 1979; Roche&Aitken 1985; Chiar & Tielens 2006).”
The evolution of amorphous hydrocarbons in the ISM: dust modelling from a new vantage point (2013, background): “Further, as shown by Chiar & Tielens (2006), a mix of amorphous olivine-type and pyroxene-type silicate materials can equally well explain the profiles of the interstellar silicate bands.”
TESTING THE UNIFICATION MODEL FOR ACTIVE GALACTIC NUCLEI IN THE INFRARED: ARE THE OBSCURING TORI OF TYPE 1 AND 2 SEYFERTS DIFFERENT? (2011, methodology): “20 In order to account for the extinction caused by the dust lane of AV ∼ 7-8 mag in Centaurus A, we have considered the Chiar & Tielens (2006) law in the fit fixing AV =8 mag.”
Intergalactic Photon Spectra from the Far-IR to the UV Lyman Limit for 0 < z < 6 and the Optical Depth of the Universe to High-Energy Gamma Rays (2005, background): “…disagreement is in the 12µm region, where our broadband photometry averages over the two peaks at higher spectral resolution produced by PAHs (polycyclic aromatic hydrocarbon) molecular emission bands (Peeters et al. 2005) and the 10 µm silicate absorption feature (Chiar & Tielens 2006).”