UNIDENTIFIED INFRARED EMISSION BANDS: PAHs or MAONs?

Kwok, Sun; Zhang, Yong

doi:10.1088/0004-637x/771/1/5

Cited by 109 publications

(64 citation statements)

References 83 publications

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“…These MOANs are, in essence, part of the same family of materials as a-C(:H). However, the MOANs appear to be much more open and less cross-linked structures than a-C(:H), and require the presence of O, N and S in the structure (Kwok & Zhang 2013), which is perhaps not supported by interstellar depletion studies.…”

Section: C4 Comparison Of Nm-sized A-c(:h) Particles With Pahsmentioning

confidence: 93%

The evolution of amorphous hydrocarbons in the ISM: dust modelling from a new vantage point

Jones

Fanciullo

Koehler

et al. 2013

A&A

410

871

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Context. The evolution of amorphous hydrocarbon materials, a-C(:H), principally resulting from ultraviolet (UV) photon absorptioninduced processing, are likely at the heart of the variations in the observed properties of dust in the interstellar medium. Aims. The consequences of the size-dependent and compositional variations in a-C(:H), from aliphatic-rich a-C:H to aromatic-rich a-C, are studied within the context of the interstellar dust extinction and emission. Methods. Newly-derived optical property data for a-C(:H) materials, combined with that for an amorphous forsterite-type silicate with iron nano-particle inclusions, a-Sil Fe , are used to explore dust evolution in the interstellar medium.Results. We present a new dust model that consists of a power-law distribution of small a-C grains and log-normal distributions of large a-Sil Fe and a-C(:H) grains. The model, which is firmly anchored by laboratory-data, is shown to quite naturally explain the variations in the infrared (IR) to far-ultraviolet (FUV) extinction, the 217 nm UV bump, the IR absorption and emission bands and the IR-mm dust emission. Conclusions. The major strengths of the new model are its inherent simplicity and built-in capacity to follow dust evolution in interstellar media. We show that mantle accretion in molecular clouds and UV photo-processing in photo-dominated regions are likely the major drivers of dust evolution.

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Section: C4 Comparison Of Nm-sized A-c(:h) Particles With Pahsmentioning

confidence: 93%

The evolution of amorphous hydrocarbons in the ISM: dust modelling from a new vantage point

Jones

Fanciullo

Koehler

et al. 2013

A&A

410

871

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“…Foing & Eherenfreund 1994;Gredel et al 2011;Herbig 1995 for a review). Some of those molecules have also been suggested to give rise to unidentified features seen in near-IR emission (e.g., Rouan et al 1997, Ruiterkamp et al 2005, Maier et al 2004Kwok & Zhang 2013). On the other hand, recent detailed analyses of DIB profiles have suggested that several of the stronger DIBs may be due to small molecules (≤ 7 heavy atoms) (Oka et al 2013;Huang & Oka 2015).…”

Section: Introductionmentioning

confidence: 99%

The Behavior of Selected Diffuse Interstellar Bands with Molecular Fraction in Diffuse Atomic and Molecular Clouds

Fan

Welty

York

et al. 2017

ApJ

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Abstract:We study the behavior of eight diffuse interstellar bands (DIBs) in different interstellar environments, as characterized by the fraction of hydrogen in molecular form (f H2 ), with comparisons to the corresponding behavior of various known atomic and molecular species. The equivalent widths of the five "normal" DIBs (ll5780.5, 5797.1, 6196.0, 6283.8, and 6613.6), normalized to E B-V , show a "Lambda-shaped" behavior: they increase at low f H2 , peak at f H2 ~ 0.3, and then decrease. The similarly normalized column densities of Ca, Ca + , Ti + , and CH + also decline for f H2 > 0.3. In contrast, the normalized column densities of Na, K, CH, CN, and CO increase monotonically with f H2 , and the trends exhibited by the three C 2 DIBs (ll4726.8, 4963.9, and 4984.8) lie between those two general behaviors. These trends with f H2 are accompanied by cosmic scatter, the dispersion at any given f H2 being significantly larger than the individual errors of measurement. The Lambda-shaped trends suggest the balance between creation and destruction of the DIB carriers differs dramatically between diffuse atomic and diffuse molecular clouds; additional processes besides ionization and shielding are needed to explain those observed trends. Except for several special cases, the highest W l (5780)/W l (5797) ratios, characterizing the so-called "sigma-zeta effect", occur only at f H2 < 0.2. We propose a sequence of DIBs based on trends in their pair-wise strength ratios with increasing f H2 . In order of increasing environmental density, we find the l6283.8 and l5780.5 DIBs, the l6196.0 DIB, the l6613.6 DIB, the l5797.1 DIB, and the C 2 DIBs.

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“…Such compounds may exist as PAHs in some cases, however, in general, they are not identical to PAHs in their properties (structure, shape, density, heat capacity, absorption cross section, etc.). Each model has its advantages and drawbacks, and the ultimate choice of some specific representation of dust properties is still to be made [6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Restructuring and destruction of hydrocarbon dust in the interstellar medium

Murga¹,

Khoperskov²,

Wiebe³

2016

Astron. Rep.

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A model of key processes influencing the evolution of a hydrocarbon grain of an arbitrary size under astrophysical conditions corresponding to ionized hydrogen regions (HII regions) and supernova remnants is presented. The considered processes include aromatization and photodestruction, sputtering by electrons and ions, and shattering due to collisions between grains. The model can be used to simulate the grain size distribution and the aromatization degree during the evolution of HII regions and supernova remnants for a specified radiation field, relative velocity of gas and dust, etc. The contribution of various processes to the evolution of hydrocarbon dust grains for parameters typical for the interstellar medium of our Galaxy is pre-

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UNIDENTIFIED INFRARED EMISSION BANDS: PAHs or MAONs?

Cited by 109 publications

References 83 publications

The evolution of amorphous hydrocarbons in the ISM: dust modelling from a new vantage point

The evolution of amorphous hydrocarbons in the ISM: dust modelling from a new vantage point

The Behavior of Selected Diffuse Interstellar Bands with Molecular Fraction in Diffuse Atomic and Molecular Clouds

Restructuring and destruction of hydrocarbon dust in the interstellar medium

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