Carbonaceous nano-dust emission in proto-planetary discs: the aliphatic-aromatic components

Boutéraon, Thomas; Habart, E.; Ysard, N.; Jones, A. P.; Dartois, E.; Pino, T.

doi:10.1051/0004-6361/201834016

Cited by 20 publications

(59 citation statements)

References 124 publications

(182 reference statements)

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“…weaker and/or narrower, see e.g. Boutéraon et al 2019 for more details about the variability of the IR-band widths) from those in the diffuse ISM. We here study dust that evolves from dense cloud dust in response to interaction with UV photons.…”

Section: Discrepancy In Irac 45 and Pacs 70mentioning

confidence: 99%

Dust evolution across the Horsehead nebula

Schirmer

Abergel

Verstraete

et al. 2020

A&A

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Context. Micro-physical processes on interstellar dust surfaces are tightly connected to dust properties (i.e. dust composition, size, and shape) and play a key role in numerous phenomena in the interstellar medium (ISM). The large disparity in physical conditions (i.e. density and gas temperature) in the ISM triggers an evolution of dust properties. The analysis of how dust evolves with the physical conditions is a stepping stone towards a more thorough understanding of interstellar dust. Aims. We highlight dust evolution in the Horsehead nebula photon-dominated region. Methods. We used Spitzer/IRAC (3.6, 4.5, 5.8 and 8 μm) and Spitzer/MIPS (24 μm) together with Herschel/PACS (70 and 160 μm) and Herschel/SPIRE (250, 350 and 500 μm) to map the spatial distribution of dust in the Horsehead nebula over the entire emission spectral range. We modelled dust emission and scattering using the THEMIS interstellar dust model together with the 3D radiative transfer code SOC. Results. We find that the nano-grain dust-to-gas ratio in the irradiated outer part of the Horsehead is 6–10 times lower than in the diffuse ISM. The minimum size of these grains is 2–2.25 times larger than in the diffuse ISM, and the power-law exponent of their size distribution is 1.1–1.4 times lower than in the diffuse ISM. In the denser part of the Horsehead nebula, it is necessary to use evolved grains (i.e. aggregates, with or without an ice mantle). Conclusions. It is not possible to explain the observations using grains from the diffuse medium. We therefore propose the following scenario to explain our results. In the outer part of the Horsehead nebula, all the nano-grain have not yet had time to re-form completely through photo-fragmentation of aggregates and the smallest of the nano-grain that are sensitive to the radiation field are photo-destroyed. In the inner part of the Horsehead nebula, grains most likely consist of multi-compositional mantled aggregates.

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Section: Discrepancy In Irac 45 and Pacs 70mentioning

confidence: 99%

Dust evolution across the Horsehead nebula

Schirmer

Abergel

Verstraete

et al. 2020

A&A

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“…Characterising the size and properties of these tiny grains through the disks, from internal to external regions, is thus A&A 649, A84 (2021) of prime importance to understand the structure and evolution of PPDs. Boutéraon et al (2019) recently reported several spatially extended near-IR spectral features that are related to aromatic and aliphatic hydrocarbon material in PPDs around Herbig stars, from 10 to 50-100 au, and even in inner gaps that are devoid of large grains. The correlation between aliphatic and aromatic CH stretching bands suggested common carriers for all features.…”

Section: Introductionmentioning

confidence: 99%

Spatial distribution of the aromatic and aliphatic carbonaceous nanograin features in the protoplanetary disk around HD 100546

Habart

Boutéraon

Brauer

et al. 2021

A&A

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Context. Carbonaceous nanograins are present at the surface of protoplanetary disks around Herbig Ae/Be stars, where most of the ultraviolet energy from the central star is dissipated. Efficiently coupled to the gas, they are unavoidable to understand the physics and chemistry of these disks. Furthermore, nanograins are able to trace the outer flaring parts of the disk and possibly the gaps from which the larger grains are missing. However, their evolution through the disks, from internal to external regions, is only poorly understood so far. Aims. Our aim is to examine the spatial distribution and evolution of the nanodust emission in the emblematic (pre-)transitional protoplanetary disk HD 100546. This disk shows many structures (annular gaps, rings, and spirals) and reveals very rich carbon nanodust spectroscopic signatures (aromatic, aliphatic) in a wide spatial range of the disk (~20−200 au). Methods. We analysed adaptive optics spectroscopic observations in the 3–4 μm range (angular resolution of ~0.1′′) and imaging and spectroscopic observations in the 8–12 μm range (angular resolution of ~0.3′′). The hyperspectral cube was decomposed into a sum of spatially coherent dust components using a Gaussian decomposition algorithm. We compared the data to model predictions using the heterogeneous dust evolution model for interstellar solids (THEMIS), which is integrated in the radiative transfer code POLARIS by calculating the thermal and stochastic heating of micro- and nanometre-sized dust grains for a given disk structure. Results. We find that the aromatic features at 3.3, 8.6, and 11.3 μm, and the aliphatic features between 3.4 and 3.5 μm are spatially extended; each band shows a specific morphology dependent on the local physical conditions. The aliphatic-to-aromatic band ratio, 3.4/3.3, increases with the distance from the star from ~0.2 (at 0.2′′ or 20 au) to ~0.45 (at 1′′ or 100 au), suggesting UV processing. In the 8–12 μm observed spectra, several features characteristic of aromatic particles and crystalline silicates are detected. Their relative contribution changes with the distance to the star. The model predicts that the features and adjacent continuum are due to different combinations of grain sub-populations, in most cases with a high dependence on the intensity of the UV field. The model reproduces the spatial emission profiles of the bands well, except for the inner 20-40 au, where the observed emission of the 3.3 and 3.4 μm bands is, unlike the predictions, flat and no longer increases with the UV field. Conclusions. With our approach that combines observational data in the near- to mid-IR and disk modelling, we deliver constraints on the spatial distribution of nano-dust particles as a function of the disk structure and radiation field.

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“…This crucial fact has driven a detailed consideration of how and where dust evolves in the diffuse and dense ISM (e.g., Stepnik et al 2003;Zhukovska et al 2008;Pino et al 2008;Bernard et al 2008;Jones et al 2013;Wang et al 2013Wang et al , 2014Wang et al , 2015aKöhler et al 2014Köhler et al , 2015Ysard et al 2016;Jones 2016a;Murga et al 2016) and how it evolves in response to the local physical conditions, e.g., gas temperature and density, interstellar radiation field (ISRF). This is particularly important in photo-dissociation regions (PDRs, e.g., Compiègne et al 2008;Abergel et al 2010;Arab et al 2012;Pilleri et al 2012Pilleri et al , 2015Joblin et al 2018) and proto-planetary discs (e.g., Klarmann et al 2017Klarmann et al , 2018Boutéraon et al 2019).…”

Section: Introductionmentioning

confidence: 99%

The essential elements of dust evolution

Jones

Ysard

2019

A&A

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Context. There remain many open questions relating to the depletion of elements into dust, e.g., exactly how are C and O incorporated into dust in dense clouds and, in particular, what drives the disappearance of oxygen in the denser interstellar medium? Aims. This work is, in part, an attempt to explain the apparently anomalous incorporation of O atoms into dust in dense clouds. Methods. We re-visit the question of the depletion of the elements incorporated into the carbonaceous component of interstellar dust, i.e., C, H, O, N and S, in the light of recent analyses of the organics in comets, meteorites and interplanetary dust particles. Results. We find that oxygen could be combined with ≈10–20 % of the carbon in the dust in dense regions in the form of a difficult to observe, organic carbonate, (−O−O>C =O), which could explain the unaccounted for 170–255 ppm oxygen depletion. Conclusions. We conclude that, while C, O and N atoms are depleted into an amorphous a-C:H:O:N phase, we posit that a significant fraction of C and O atoms could be sequestered into an organic carbonate, which provides a viable solution to the oxygen depletion problem. Further, the thermal or photolytic decomposition of this carbonate may have a bearing on the formation of CO2 in the ISM.

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Carbonaceous nano-dust emission in proto-planetary discs: the aliphatic-aromatic components

Cited by 20 publications

References 124 publications

Dust evolution across the Horsehead nebula

Dust evolution across the Horsehead nebula

Spatial distribution of the aromatic and aliphatic carbonaceous nanograin features in the protoplanetary disk around HD 100546

The essential elements of dust evolution

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