The galactic center - 16-30 micron observations and the 18 micron extinction

McCarthy, John F.; Forrest, W. J.; Briotta, D. A.; Houck, J. R.

doi:10.1086/158528

Cited by 30 publications

(15 citation statements)

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“…The agreement at 12.5 µm allows a limit on source variability to be set at less than 30% over 5 years. The data show strong silicate absorption centered near 9.7 µm (rest wavelength), but there is no clear indication of silicate absorption centered near 18 µm (rest wavelength) such as that seen toward the Galactic Center (McCarthy et al 1980). No detectable evidence of the 11.3 µm PAH emission feature (F(11.3µm)≤0.7×10 −15 W m −2 3σ) is observed.…”

Section: Resultsmentioning

confidence: 73%

The Deep Silicate Absorption Feature in IRAS 08572+3915 and Other Infrared Galaxies

Dudley

Wynn‐Williams

1997

ApJ

105

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New mid-infrared (10 and 20 km) spectrophotometry of the ultraluminous infrared galaxy IRAS 08572]3915 is presented. The 10 km spectrum reveals a deep silicate absorption feature, while the 20 km spectrum shows no clear evidence for an 18 km silicate absorption feature. An interstellar extinction curve is Ðtted to IRAS 08572]3915 and two other deep silicate infrared galaxies, NGC 4418 and Arp 220. It is found that pure extinction cannot explain the spectral energy distributions of these sources. On the other hand, both the strength of the silicate absorption and the overall spectral energy distributions of the three galaxies agree well with scaled-up models of galactic protostars. From this agreement, we conclude that the infrared emission comes from an optically thick dust shell surrounding a compact power source. The size of the power source is constrained to be smaller than a few parsecs. We argue that a signiÐcant portion of the total luminosities of these galaxies arises from an active galactic nucleus deeply embedded in dust.

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Section: Resultsmentioning

confidence: 73%

The Deep Silicate Absorption Feature in IRAS 08572+3915 and Other Infrared Galaxies

Dudley

Wynn‐Williams

1997

ApJ

105

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“…An additional problem is the ubiquitous presence of the 9.7 and 18 μm silicate absorption features toward the Galactic Center (McCarthy et al 1980;Fritz et al 2011;Roche et al 2015, and references therein). The features are attributed to the Si-O stretching and O-Si-O bending modes in silicates comprised of SiO 4 tetrahedra (Khanna et al 1981).…”

Section: Discussionmentioning

confidence: 99%

Iron: A Key Element for Understanding the Origin and Evolution of Interstellar Dust

Dwek

2016

ApJ

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The origin and depletion of iron differ from all other abundant refractory elements that make up the composition of interstellar dust. Iron is primarily synthesized in Type Ia supernovae (SNe Ia) and in core collapse supernovae (CCSN), and is present in the outflows from AGB stars. Only the latter two are observed to be sources of interstellar dust since searches for dust in SN Ia have provided strong evidence for the absence of any significant mass of dust in their ejecta. Consequently, more than 65% of the iron is injected into the ISM in gaseous form. Yet ultraviolet and X-ray observations along many lines of sight in the ISM show that iron is severely depleted in the gas phase as compared to expected solar abundances. The missing iron, comprising about 90% of the total, is believed to be locked up in interstellar dust. This suggests that most of the missing iron must have precipitated from the ISM gas by a cold accretion onto preexisting silicate, carbon, or composite grains. Iron is thus the only element that requires most of its growth to occur outside the traditional stellar condensation sources. This is a robust statement that does not depend on our evolving understanding of the dust destruction efficiency in the ISM. Reconciling the physical, optical, and chemical properties of such composite grains with their many observational manifestations is a major challenge for understanding the nature and origin of interstellar dust.

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“…This conclusion is strengthened by the fact that a 10 µm emission feature is observed in outflows from cool oxygen-rich stars (which would be expected to condense silicate dust) but not in the outflows from carbon-rich stars (where silicates do not form, because all of the oxygen is locked up in CO). There is also a broad feature at 18 µm which is presumed to be the O-Si-O bending mode in silicates (McCarthy et al 1980;Smith et al 2000).…”

Section: Silicate Featuresmentioning

confidence: 99%

Interstellar Dust Grains

Draine

2003

Annu. Rev. Astron. Astrophys.

2,214

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This review surveys the observed properties of interstellar dust grains: the wavelength-dependent extinction of starlight, including absorption features, from UV to infrared; optical luminescence; infrared emission; microwave emission; optical, UV, and X-ray scattering by dust; and polarization of starlight and of infrared emission. The relationship between presolar grains in meteorites and the interstellar grain population is discussed. Candidate grain materials and abundance constraints are considered. A dust model consisting of amorphous silicate grains, graphite grains, and polycyclic aromatic hydrocarbons is compared with observed emission and scattering. Some issues concerning evolution of interstellar dust are discussed.

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The galactic center - 16-30 micron observations and the 18 micron extinction

Cited by 30 publications

References 0 publications

The Deep Silicate Absorption Feature in IRAS 08572+3915 and Other Infrared Galaxies

The Deep Silicate Absorption Feature in IRAS 08572+3915 and Other Infrared Galaxies

Iron: A Key Element for Understanding the Origin and Evolution of Interstellar Dust

Interstellar Dust Grains

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