Modeling of protostellar clouds and their observational properties

Жилкин, А. Г.; Pavlyuchenkov, Ya. N.; Zamozdra, S. N.

doi:10.1134/s1063772909070026

Cited by 13 publications

(25 citation statements)

References 40 publications

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“…Indeed for gas densities lower than 10 5 H/cm 3 , a mild dust-gas coupling is expected. In this case, the dust grains are usually colder than the gas by 2−3 K, especially when the grain growth is taken into account because it further decreases the dust-gas coupling (Zhilkin et al 2009;Juvela & Ysard 2011;Nielbock et al 2012). This indicates that the gas temperature in Pagani et al (2010a) may have been slightly underestimated.…”

Section: Third Cutmentioning

confidence: 99%

Variation in dust properties in a dense filament of the Taurus molecular complex (L1506)

Ysard

Abergel

Ristorcelli

et al. 2013

A&A

107

121

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Aims. We observed the L1506 filament, which is located in the Taurus molecular complex, with the Herschel PACS and SPIRE instruments. Our aim is to prove the variation in grain properties along the entire length of the filament. In particular, we want to determine above which gas density this variation arises and what changes in the grain optical properties/size distribution are required. Methods. We use the 3D radiative transfer code CRT, coupled to the dust emission and extinction code DustEM, to model the emission and extinction of the dense filament. We test a range of optical properties and size distributions for the grains: dust of the diffuse interstellar medium (interstellar PAHs and amorphous carbons and silicates) and both compact and fluffy aggregates. Results. We find that the grain opacity has to increase across the filament to fit simultaneously the near-IR extinction and Herschel emission profiles of L1506. We interpret this change to be a consequence of the coagulation of dust grains to form fluffy aggregates. Grains similar to those in the diffuse medium have to be present in the outer layers of the cloud, whereas aggregates must prevail above gas densities of a few 10 3 H/cm 3 . This corresponds to line-of-sights with visual extinction in the V band of the order of 2 to 3. The dust opacity at 250 μm is raised by a factor of 1.8 to 2.2, while the grain average size is increased by a factor of 5. These exact numbers depend naturally on the dust model chosen to fit the data. Our findings agree with the constraints given by the study of the gas molecular lines. Using a simple approach, we show that the aggregates may have time to form inside the filament within the cloud lifetime. Our model also characterises the density structure of the filament, showing that the filament width is not constant along L1506 but instead varies by a factor of the order of 4. Conclusions. We confirm the need for an increase in the far-IR dust opacity to explain the emission and extinction in L1506C, which we interpret as being due to dust growth. We also show that this opacity variation is valid along the entire length of the L1506 dense filament.

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Section: Third Cutmentioning

confidence: 99%

Variation in dust properties in a dense filament of the Taurus molecular complex (L1506)

Ysard

Abergel

Ristorcelli

et al. 2013

A&A

107

121

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“…Hotzel et al 2002a;Bergin et al 2006), and generally one would expect both the gas and the dust temperature to be tightly coupled in the core centre, where they experience densities of n H ≥ 10 5 cm −3 (e.g. Lesaffre et al 2005;Zhilkin et al 2009), with the strength of the coupling gradually increasing already from n H ≈ 10 4 cm −3 (Goldsmith 2001). However, Bergin et al (2006) found evidence that this might not be necessarily the case.…”

Section: The Temperature Distributionmentioning

confidence: 99%

“…This can lead to diverging gas and dust temperatures in the centre of dense cores (e.g. Zhilkin et al 2009). According to Bergin et al (2006), this can only be explained by a reduced gas-to-dust coupling in the centre of B68, especially when -as in this case -the gas is strongly depleted.…”

Section: The Temperature Distributionmentioning

confidence: 99%

The Earliest Phases of Star formation (EPoS) observed withHerschel: the dust temperature and density distributions of B68

Nielbock

Launhardt

Steinacker

et al. 2012

A&A

129

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Context. Isolated starless cores within molecular clouds can be used as a testbed to investigate the conditions prior to the onset of fragmentation and gravitational proto-stellar collapse. Aims. We aim to determine the distribution of the dust temperature and the density of the starless core B68. Methods. In the framework of the Herschel guaranteed-time key programme "The Earliest Phases of Star formation" (EPoS), we have imaged B68 between 100 and 500 μm. Ancillary data at (sub)millimetre wavelengths, spectral line maps of the 12 CO (2-1), and 13 CO (2-1) transitions, as well as an NIR extinction map were added to the analysis. We employed a ray-tracing algorithm to derive the 2D mid-plane dust temperature and volume density distribution without suffering from the line-of-sight averaging effects of simple SED fitting procedures. Additional 3D radiative transfer calculations were employed to investigate the connection between the external irradiation and the peculiar crescent-shaped morphology found in the FIR maps. Results. For the first time, we spatially resolve the dust temperature and density distribution of B68, convolved to a beam size of 36. 4. We find a temperature gradient dropping from (16.7 ) × 10 5 cm −3 . B68 has a mass of 3.1 M of material with A K > 0.2 mag for an assumed distance of 150 pc. We detect a compact source in the southeastern trunk, which is also seen in extinction and CO. At 100 and 160 μm, we observe a crescent of enhanced emission to the south. Conclusions. The dust temperature profile of B68 agrees well with previous estimates. We find the radial density distribution from the edge of the inner plateau outward to be n H ∝ r −3.5 . Such a steep profile can arise from either or both of the following: external irradiation with a significant UV contribution or the fragmentation of filamentary structures. Our 3D radiative transfer model of an externally irradiated core by an anisotropic ISRF reproduces the crescent morphology seen at 100 and 160 μm. Our CO observations show that B68 is part of a chain of globules in both space and velocity, which may indicate that it was once part of a filament that dispersed. We also resolve a new compact source in the southeastern trunk and find that it is slightly shifted in centroid velocity from B68, lending qualitative support to core collision scenarios.

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“…This is a two-dimensional code for modelling the axysymmetric MHD flows (Dudorov et al 1999;Zhilkin et al 2009). The code is based on the explicit quasi-monotonic TVD-scheme of high order of accuracy.…”

Section: Numerical Codementioning

confidence: 99%

Hierarchical structure of the interstellar molecular clouds and star formation

Dudorov

Khaibrakhmanov

2017

Open Astronomy

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Properties of the hierarchical structures of interstellar molecular clouds are discussed. Particular attention is paid to the statistical correlations between velocity dispersion and size, and between the magnetic field strength and gas density. We investigate the formation of some hierarchical structures with the help of numerical MHD simulations using the ENLIL code. The simulations show that the interstellar molecular filaments with parallel magnetic field and molecular cores can form via the collapse and fragmentation of cylindrical molecular clouds. The parallel magnetic field halts the radial collapse of the cylindrical cloud maintaining its nearly constant radius ∼0.1 pc. The observed filaments with perpendicular magnetic field can form as a result of the magnetostatic contraction of oblate molecular clouds under the action of Alfvén and MHD turbulence. The theoretical density profiles are fitted with the Plummer-like function and agree with observed profiles of the filaments in Gould's Belt. The characteristics of molecular cloud cores found in our simulations are in agreement with observations.

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Modeling of protostellar clouds and their observational properties

Cited by 13 publications

References 40 publications

Variation in dust properties in a dense filament of the Taurus molecular complex (L1506)

Variation in dust properties in a dense filament of the Taurus molecular complex (L1506)

The Earliest Phases of Star formation (EPoS) observed withHerschel: the dust temperature and density distributions of B68

Hierarchical structure of the interstellar molecular clouds and star formation

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