Query : 2012A&A...542A..98J

2012A&A...542A..98J - Astronomy and Astrophysics, volume 542A, 98-98 (2012/6-1)

Variations on a theme - the evolution of hydrocarbon solids. III. Size-dependent properties - the optEC(s)(a) model.


Abstract (from CDS):

The properties of hydrogenated amorphous carbon (a-C:H) dust evolve in response to the local radiation field in the interstellar medium (ISM) and the evolution of these properties is particularly dependent upon the particle size. A model for finite-sized, low-temperature amorphous hydrocarbon particles, based on the microphysical properties of random and defected networks of carbon and hydrogen atoms, with surfaces passivated by hydrogen atoms, has been developed. The eRCN/DG and the optEC(s) models have been combined, adapted and extended into a new optEC(s)(a) model that is used to calculate the optical properties of hydrocarbon grain materials down into the sub-nanometre size regime, where the particles contain only a few tens of carbon atoms. The optEC(s)(a) model predicts a continuity in properties from large to small (sub-nm) carbonaceous grains. Tabulated data of the size-dependent optical constants (from EUV to cm wavelengths) for a-C:H (nano-)particles as a function of the bulk material band gap [Eg(bulk)], or equivalently the hydrogen content, are provided. The effective band gap [Eg(eff.)] is found to be significantly larger than Eg(bulk) for hydrogen-poor a-C(:H) nano-particles and their predicted long-wavelength (λ> 30µm) optical properties differ from those derived for interstellar polycyclic aromatic hydrocarbons (PAHs). The optEC(s)(a) model is used to investigate the size-dependent structural and spectral evolution of a-C(:H) materials under ISM conditions, including: the IR-FUV extinction, the 217nm bump and the infrared emission bands. The model makes several predictions that can be tested against observations.

Abstract Copyright:

Journal keyword(s): dust, extinction - ISM: general - ISM: molecules

VizieR on-line data: <Available at CDS (J/A+A/542/A98): k0_33nm.dat k0_5nm.dat k100nm.dat k10nm.dat k1nm.dat k30nm.dat k3nm.dat n0_33nm.dat n0_5nm.dat n100nm.dat n10nm.dat n1nm.dat n30nm.dat n3nm.dat>

Errata: + corrigendum vol. 545, p. C3

Simbad objects: 4

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Number of rows : 4
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
1 M 82 AG? 09 55 52.430 +69 40 46.93 9.61 9.30 8.41     ~ 5781 6
2 NAME Galactic Center reg 17 45 39.60213 -29 00 22.0000           ~ 14048 0
3 GCIRS 6E WR* 17 45 39.632 -29 00 27.05           Ofpe/WN9 64 0
4 Schulte 12 s*b 20 32 40.9572199728 +41 14 29.279036940 16.1 14.45 11.702     B3-4Ia+ 412 0

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