Chemical Evolution of Carbonaceous Material in Interstellar Clouds

Duley, W. W.

doi:10.1086/308204

Cited by 64 publications

(41 citation statements)

References 43 publications

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“…In partially graphitized coals like semianthracite that have been proposed to account for mid-infrared emission features , these BSUs are interconnected by aliphatic side-groups or by hetero-atoms. These various approaches of interstellar dust particles are really complementary, as shown by Duley (2000).…”

Section: Discussion/astrophysical Implicationsmentioning

confidence: 93%

“…But the existence of such substituted cumulene-containing aromatic molecules is quite plausible both from the chemical point of view (Norman et al 1999), and particularly from the astrophysical one, since they are suggested by the analysis of infrared spectra (Duley 2000) and free cumulene chains have been widely detected in molecular clouds (Cernicharo et al 1991;Langer et al 1997). Moreover it has been recently established that chains like C 2 H or C 4 H are also abundant in photodissociation regions, despite the strong UV field.…”

Section: Photoinduced Productsmentioning

confidence: 99%

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Photoinduced products from cold coronene clusters

Bréchignac¹,

Schmidt

Masson

et al. 2005

A&A

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Free cold pure coronene clusters have been formed in a gas aggregation source and irradiated with excimer laser pulses. Analysis of the photoproducts thanks to a reflectron time-of-flight mass spectrometer showed that new ionic compounds are formed. These species may include Polycyclic Aromatic Hydrocarbons (PAHs) larger than coronene, PAH-coronene clusters, as well as coronene clusters branched with unsaturated aliphatic chains. The relevance of these results in the context of interstellar medium chemistry, and in particular the carriers of the so-called aromatic infrared emission bands (AIBs), is discussed.

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Section: Discussion/astrophysical Implicationsmentioning

confidence: 93%

Section: Photoinduced Productsmentioning

confidence: 99%

Photoinduced products from cold coronene clusters

Bréchignac¹,

Schmidt

Masson

et al. 2005

A&A

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“…In contrast, the smaller, stochastically-heated grains, will be converted to hydrogen-poorer, lower density, smaller bandgap, aromatic-rich materials. The photo-fragmentation of the smaller, aromatic-rich grains could then be an important source of molecular aromatic species such as PAH s and molecular fragments (e.g., Jones 1990;Duley 2000;Petrie et al 2003;Pety et al 2005;Jones 2005Jones , 2009). …”

Section: The Nature Of Interstellar Carbon Grainsmentioning

confidence: 99%

The global dust SED: tracing the nature and evolution of dust with DustEM

Compiègne

Verstraete

Jones

et al. 2010

A&A

404

724

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The Planck and Herschel missions are currently measuring the far-infrared to millimeter emission of dust, which combined with existing IR data, will for the first time provide the full spectral energy distribution (SED) of the galactic interstellar medium dust emission, from the mid-IR to the mm range, with an unprecedented sensitivity and down to spatial scales ∼30 . Such a global SED will allow a systematic study of the dust evolution processes (e.g. grain growth or fragmentation) that directly affect the SED because they redistribute the dust mass among the observed grain sizes. The dust SED is also affected by variations of the radiation field intensity. Here we present a versatile numerical tool, DustEM, that predicts the emission and extinction of dust grains given their size distribution and their optical and thermal properties. In order to model dust evolution, DustEM has been designed to deal with a variety of grain types, structures and size distributions and to be able to easily include new dust physics. We use DustEM to model the dust SED and extinction in the diffuse interstellar medium at high-galactic latitude (DHGL), a natural reference SED that will allow us to study dust evolution. We present a coherent set of observations for the DHGL SED, which has been obtained by correlating the IR and HI-21 cm data. The dust components in our DHGL model are (i) polycyclic aromatic hydrocarbons; (ii) amorphous carbon and (iii) amorphous silicates. We use amorphous carbon dust, rather than graphite, because it better explains the observed high abundances of gas-phase carbon in shocked regions of the interstellar medium. Using the DustEM model, we illustrate how, in the optically thin limit, the IRAS/Planck HFI (and likewise Spitzer/Herschel for smaller spatial scales) photometric band ratios of the dust SED can disentangle the influence of the exciting radiation field intensity and constrain the abundance of small grains (a < ∼ 10 nm) relative to the larger grains. We also discuss the contributions of the different grain populations to the IRAS, Planck (and similarly to Herschel) channels. Such information is required to enable a study of the evolution of dust as well as to systematically extract the dust thermal emission from CMB data and to analyze the emission in the Planck polarized channels. The DustEM code described in this paper is publically available.

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“…Another wagging mode involving H atoms in Cu(CH) i C structures occurs near 12 mm, while other bending modes in i (CH 2 ) i (CH 2 ) i are seen at 12.8 and 13.5 mm (Colthup 1990). The role that such nonaromatic compounds might play in interstellar sources has been discussed by Duley (2000). These need not be separate molecules as groups of this kind could be attached to PAHs (see Fig.…”

Section: Results and Analysismentioning

confidence: 99%

Laboratory Simulation of 11-15 μm Spectra Associated with Polycyclic Aromatic Hydrocarbon Molecules

Hu¹,

Duley²

2007

ApJ

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We have obtained 11-15 mm spectra of thin films of hydrogenated amorphous carbon assembled from carbon nanoparticles. Well-defined, narrow features similar to the interstellar emission bands attributed to polycyclic aromatic hydrocarbons (PAHs) are observed at 11.3, 12, 12.8, 13.5, and 14.2 mm. These features are reproduced in many samples prepared under a variety of conditions, indicating that they involve common molecular components. We suggest that these are based on compact ring structures such as coronene, C 24 H 12 , but that these molecules have peripheral substitutions involving additional aromatic rings. They may also be substituted with sp-or sp 2 -bonded carbon chains. All bands exhibit slight energy shifts in different samples in response to changes in preparation conditions. These shifts replicate variations in wavelength and profile of the 11-15 mm bands seen in different type of emission source. None of the nanoparticle samples exhibit all of the 11.3, 12, 12.8, 13.5, and 14.2 mm features. This implies that the interstellar bands are produced by a limited variety of PAH structures, rather than by a single dominant species.

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Chemical Evolution of Carbonaceous Material in Interstellar Clouds

Cited by 64 publications

References 43 publications

Photoinduced products from cold coronene clusters

Photoinduced products from cold coronene clusters

The global dust SED: tracing the nature and evolution of dust with DustEM

Laboratory Simulation of 11-15 μm Spectra Associated with Polycyclic Aromatic Hydrocarbon Molecules

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