Probing the Role of Carbon in Ultraviolet Extinction Along Galactic Sight Lines

Parvathi, V. S.; Sofia, U. J.; Murthy, Jayant; Babu, B. R. S.

doi:10.1088/0004-637x/760/1/36

Cited by 70 publications

(147 citation statements)

References 32 publications

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“…As discussed by Jones et al (2013Jones et al ( , 2014, carbon accretion and the formation of a-C(:H) mantles appears to be consistent with the observed carbon depletion and allied variations in the extinction curve (Parvathi et al 2012;Jones et al 2013). It now appears that carbon could be more abundant in the ISM than previously assumed (e.g., 355 ± 64 ppm, Parvathi et al 2012), which if we assume that 200 ppm are in dust in the diffuse ISM Ysard et al 2015) would leave 155 ±64 ppm in the gas in the form of CO (and other molecules) and available for carbonaceous mantle formation in the transition from the diffuse ISM to denser regions .…”

Section: Astrophysical Implications and Consequencessupporting

confidence: 77%

“…Thus, C and H atom accretion from the gas phase and/or surface hydrogenation in a moderately extinguished medium (0.5 < ∼ A V < ∼ 2) could lead to the formation of a-C:H mantles on all grains. The characteristic extinction properties of this material are a strong FUV extinction and a weak UV bump, as observed along the line of sight towards HD 207198, which shows a high carbon depletion (i.e., (C/H) dust = 395 ± 61 ppm, Parvathi et al 2012). …”

Section: A-c:h Formationmentioning

confidence: 70%

“…Recent work by Parvathi et al (2012) indicates a total interstellar carbon abundance of (C/H) total 355 ± 64 ppm and, with 200 ppm in dust in the diffuse ISM Ysard et al 2015), there is likely a large reservoir of gas phase carbon ( 155 ± 64 ppm) in the low density ISM that could accrete onto dust in denser regions. In low extinction regions (A V < ∼ 0.5) a-C(:H) grain mantles will be composed of a-C because of photo-processing/dehydrogenation by EUV-UV photons (Jones 2012a,b;Jones et al 2013Jones et al , 2014.…”

Section: A-c:h Formationmentioning

confidence: 99%

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Mantle formation, coagulation, and the origin of cloud/core shine

Jones

Koehler

Ysard

et al. 2016

A&A

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Context. The observed cloudshine and coreshine (C-shine) have been explained in terms of grain growth leading to enhanced scattering from clouds in the J, H, and K photometric bands and the Spitzer IRAC 3.6 and 4.5 μm bands. Aims. Using our global dust-modelling approach THEMIS (The Heterogeneous dust Evolution Model at the IaS), we explore the effects of dust evolution in dense clouds, through aliphatic-rich carbonaceous mantle formation and grain-grain coagulation. Methods. We model the effects of wide band gap a-C:H mantle formation and the low-level aggregation of diffuse interstellar medium dust in the moderately-extinguished outer regions of molecular clouds. Results. The formation of wide band gap a-C:H mantles on amorphous silicate and amorphous carbon (a-C) grains leads to a decrease in their absorption cross-sections but no change in their scattering cross-sections at near-infrared wavelengths, resulting in higher albedos. Conclusions. The evolution of dust, with increasing density and extinction in the diffuse-to-dense molecular cloud transition, through mantle formation and grain aggregation, appears to be a likely explanation for the observed C-shine.

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Section: Astrophysical Implications and Consequencessupporting

confidence: 77%

Section: A-c:h Formationmentioning

confidence: 70%

Section: A-c:h Formationmentioning

confidence: 99%

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Mantle formation, coagulation, and the origin of cloud/core shine

Jones

Koehler

Ysard

et al. 2016

A&A

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“…15 This is consistent with the high carbon depletion (∼ 400 ppm of C in dust) along the line of sight towards HD 207198 5,15 but inconsistent with the extinction curve along lines of sight through the denser diffuse ISM, with R V ∼ 5, where the UV extinction is flatter than the average, i.e., for lines of sight with R V ∼ 3. The flatter UV extinction along high R V lines of sight implies that the coagulation of small grains onto large grains occurs before or is contemporaneous with carbonaceous mantle accretion.…”

Section: Astrophysical Implicationsmentioning

confidence: 76%

“…[1][2][3][4][5][6][7][8] Recent work strongly suggests that these grains most likely consist of hydrogenated amorphous carbons, a-C(:H), which encompass H-poor, aromatic-rich a-C through to H-rich, aliphatic-rich a-C:H materials. [9][10][11][12][13][14][15] Such hydrocarbon nano-particles are processed in the intense radiation fields of photodissociation regions (PDRs) by UV photon-induced destruction 6,15 and by ion and electron collisions.…”

Section: Introductionmentioning

confidence: 99%

The cycling of carbon into and out of dust

et al. 2014

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Observational evidence seems to indicate that the depletion of interstellar carbon into dust shows rather wide variations and that carbon undergoes rather rapid recycling in the interstellar medium (ISM). Small hydrocarbon grains are processed in photo-dissociation regions by UV photons and by ion and electron collisions in interstellar shock waves and by cosmic rays. A significant fraction of hydrocarbon dust must therefore be re-formed by accretion in the dense, molecular ISM. A new dust model [Jones et al., A&A, 2013, 558, A62] shows that variations in the dust observables, in the diffuse interstellar medium (n H ≤ 10 3 cm −3 ), can be explained by systematic and environmentally-driven changes in the small hydrocarbon grain population. Here we explore the consequences of gas-phase carbon accretion onto the surfaces of grains in the transition regions between the diffuse ISM and molecular clouds [e.g., Jones, A&A, 2013, 555, A39]. We find that significant carbonaceous dust re-processing and/or mantle accretion can occur in the outer regions of molecular clouds and that this dust will have significantly different optical properties from the dust in the adjacent diffuse ISM. We conclude that the (re-)processing and cycling of carbon into and out of dust is perhaps the key to advancing our understanding of dust evolution in the ISM.

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Dust Polarisation in the Interstellar Medium

Siebenmorgen

Peest

2019

Astrophysics and Space Science Library

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Probing the Role of Carbon in Ultraviolet Extinction Along Galactic Sight Lines

Cited by 70 publications

References 32 publications

Mantle formation, coagulation, and the origin of cloud/core shine

Mantle formation, coagulation, and the origin of cloud/core shine

The cycling of carbon into and out of dust

Dust Polarisation in the Interstellar Medium

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