Dust coagulation and fragmentation in molecular clouds

Ormel, Chris W.; Min, M.; Tielens, A. G. G. M.; Dominik, C.; Paszun, D.

doi:10.1051/0004-6361/201117058

Cited by 156 publications

(196 citation statements)

References 58 publications

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“…The same dust model was adopted in Paper I (κ 870 μm 0.17 m 2 kg −1 ), and is expected to be a reasonable model for cold, dense molecular cloud cores 9 . We note that the sub-mm opacities recently calculated by Ormel et al (2011) are comparable to the OH94 values (after 9 For comparison, for dust grains covered by thin ice mantles at a density 10 5 cm −3 , κ 350 μm 0.78 m 2 kg −1 . The κ 350 μm value we have adopted is the same as in the OH94 model of grains with thin ice mantles at a density 10 6 cm −3 .…”

Section: Core Properties Derived From 350 μM Emissionsupporting

confidence: 71%

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A (sub)millimetre study of dense cores in Orion B9

Miettinen

Harju

Haikala

et al. 2012

A&A

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Context. Studies of dense molecular-cloud cores at (sub)millimetre wavelengths are needed to understand the early stages of star formation. Aims. We aim to further constrain the properties and evolutionary stages of dense cores in Orion B9. The prime objective of this study is to examine the dust emission of the cores near the peak of their spectral energy distributions, and to determine the degrees of CO depletion, deuterium fractionation, and ionisation. Methods. The central part of Orion B9 was mapped at 350 μm with APEX/SABOCA. A sample of nine cores in the region were observed in C 17 O(2−1), H 13 CO + (4−3) (towards 3 sources), DCO + (4−3), N 2 H + (3−2), and N 2 D + (3−2) with APEX/SHFI. These data are used in conjunction with our previous APEX/LABOCA 870-μm dust continuum data. Results. All the LABOCA cores in the region covered by our SABOCA map were detected at 350 μm. The strongest 350 μm emission is seen towards the Class 0 candidate SMM 3. Many of the LABOCA cores show evidence of substructure in the higher-resolution SABOCA image. In particular, we report on the discovery of multiple very low-mass condensations in the prestellar core SMM 6. Based on the 350-to-870 μm flux density ratios, we determine dust temperatures of T dust 7.9−10.8 K, and dust emissivity indices of β ∼ 0.5−1.8. The CO depletion factors are in the range f D ∼ 1.6−10.8. The degree of deuteration in N 2 H + is 0.04−0.99, where the highest value (seen towards the prestellar core SMM 1) is, to our knowledge, the most extreme level of N 2 H + deuteration reported so far. The level of HCO + deuteration is about 1-2%. The fractional ionisation and cosmic-ray ionisation rate of H 2 could be determined only towards two sources with the lower limits of ∼2−6 × 10 −8 and ∼2.6 × 10 −17 −4.8 × 10 −16 s −1 , respectively. We also detected D 2 CO towards two sources. Conclusions. The detected protostellar cores are classified as Class 0 objects, in agreement with our previous SED results. The detection of subcondensations within SMM 6 shows that core fragmentation can already take place during the prestellar phase. The origin of this substructure is likely caused by thermal Jeans fragmentation of the elongated parent core. Varying levels of f D and deuteration among the cores suggest that they are evolving chemically at different rates. A low f D value and the presence of gas-phase D 2 CO in SMM 1 suggest that the core chemistry is affected by the nearby outflow. The very high N 2 H + deuteration in SMM 1 is likely to be remnant of the earlier CO-depleted phase.

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Section: Core Properties Derived From 350 μM Emissionsupporting

confidence: 71%

“…10 5 yr of coagulation). However, the dust opacities are likely to be uncertain by a factor of 2 (e.g., OH94; Motte & André 2001;Ormel et al 2011). For the average dust-to-gas mass ratio, R d ≡ M dust /M gas , we adopted the canonical value 1/100.…”

Section: Core Properties Derived From 350 μM Emissionmentioning

confidence: 99%

A (sub)millimetre study of dense cores in Orion B9

Miettinen

Harju

Haikala

et al. 2012

A&A

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“…The scattering feature before the edge is better fitted using a model with larger particles, which leads to the possibility of the presence of particles larger than 0.25 µm. It is possible that in environments such as the Galactic center region we observe a substantial amount of particles larger than 0.25 µm (Ossenkopf et al 1992;Ormel et al 2009Ormel et al , 2011. In our analysis, we assume that the dust particles are solid spheres, while it is more likely that large particles in dense environments are grown by coagulation of dust particles (Jura 1980).…”

Section: Scattering and Particle Size Distributionsmentioning

confidence: 98%

“…The sight line toward GX 5-1 traverses the molecular ring and likely probes a mixture of diffuse and dense medium. The dense region may be associated with the molecular ring, characterized by larger grains (Ormel et al 2009(Ormel et al , 2011.…”

Section: Scattering and Particle Size Distributionsmentioning

confidence: 99%

Absorption and scattering by interstellar dust in the silicon K-edge of GX 5-1

Zeegers

Costantini

Vries

et al. 2017

A&A

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Context. We study the absorption and scattering of X-ray radiation by interstellar dust particles, which allows us to access the physical and chemical properties of dust. The interstellar dust composition is not well understood, especially on the densest sight lines of the Galactic Plane. X-rays provide a powerful tool in this study. Aims. We present newly acquired laboratory measurements of silicate compounds taken at the Soleil synchrotron facility in Paris using the Lucia beamline. The dust absorption profiles resulting from this campaign were used in this pilot study to model the absorption by interstellar dust along the line of sight of the low-mass X-ray binary (LMXB) GX 5-1. Methods. The measured laboratory cross-sections were adapted for astrophysical data analysis and the resulting extinction profiles of the Si K-edge were implemented in the SPEX spectral fitting program. We derive the properties of the interstellar dust along the line of sight by fitting the Si K-edge seen in absorption in the spectrum of GX 5-1. Results. We measured the hydrogen column density towards GX 5-1 to be 3.40 ± 0.1 × 10 22 cm −2 . The best fit of the silicon edge in the spectrum of GX 5-1 is obtained by a mixture of olivine and pyroxene. In this study, our modeling is limited to Si absorption by silicates with different Mg:Fe ratios. We obtained an abundance of silicon in dust of 4.0 ± 0.3 × 10 −5 per H atom and a lower limit for total abundance, considering both gas and dust, of > 4.4 × 10 −5 per H atom, which leads to a gas to dust ratio of > 0.22. Furthermore, an enhanced scattering feature in the Si K-edge may suggest the presence of large particles along the line of sight.

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“…In clouds, grains are protected from UV irradiation and sputtering in shocks, and the dust mass can grow by accretion of gas-phase species (Greenberg 1982;Draine 2009). Coagulation becomes the dominant outcome of grain-grain collisions in dense clouds, resulting in the removal of small grains and the build-up of large grains (Hirashita & Yan 2009;Ormel et al 2011).…”

Section: Introductionmentioning

confidence: 99%

The turbulent life of dust grains in the supernova-driven, multiphase interstellar medium

Peters

Zhukovska

Naab

et al. 2017

Monthly Notices of the Royal Astronomical Society

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Dust grains are an important component of the interstellar medium (ISM) of galaxies. We present the first direct measurement of the residence times of interstellar dust in the different ISM phases, and of the transition rates between these phases, in realistic hydrodynamical simulations of the multi-phase ISM. Our simulations include a timedependent chemical network that follows the abundances of H + , H, H 2 , C + and CO and take into account self-shielding by gas and dust using a tree-based radiation transfer method. Supernova explosions are injected either at random locations, at density peaks, or as a mixture of the two. For each simulation, we investigate how matter circulates between the ISM phases and find more sizeable transitions than considered in simple mass exchange schemes in the literature. The derived residence times in the ISM phases are characterised by broad distributions, in particular for the molecular, warm and hot medium. The most realistic simulations with random and mixed driving have median residence times in the molecular, cold, warm and hot phase around 17, 7, 44 and 1 Myr, respectively. The transition rates measured in the random driving run are in good agreement with observations of Ti gas-phase depletion in the warm and cold phases in a simple depletion model, although the depletion in the molecular phase is under-predicted. ISM phase definitions based on chemical abundance rather than temperature cuts are physically more meaningful, but lead to significantly different transition rates and residence times because there is no direct correspondence between the two definitions.

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Dust coagulation and fragmentation in molecular clouds

Cited by 156 publications

References 58 publications

A (sub)millimetre study of dense cores in Orion B9

A (sub)millimetre study of dense cores in Orion B9

Absorption and scattering by interstellar dust in the silicon K-edge of GX 5-1

The turbulent life of dust grains in the supernova-driven, multiphase interstellar medium

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