Self-gravitating filament formation from shocked flows: velocity gradients across filaments

Chen, Che-Yu; Mundy, Lee G.; Ostriker, Eve C.; Storm, Shaye; Dhabal, Arnab

doi:10.1093/mnras/staa960

Cited by 44 publications

(47 citation statements)

References 64 publications

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“…Velocity gradients perpendicular to filaments have been found in other clouds as well, e.g. : DR21 (Schneider et al 2010), IRDC 18223 (Beuther et al 2015), Serpens (Dhabal et al 2018;Chen et al 2020) and SDC13 (Williams et al 2018). In these studies, the observed velocity gradients have also found to be possible indications of mass accretion by the filament from inflowing lower-density gas.…”

Section: Continuous Mass Accretion On the Filament Crest In Muscasupporting

confidence: 55%

“…Here we compare the typical observed relative motions between the crest and the surrounding gas with the expected self-gravity velocities to discuss at which scale gravity may be responsible for the observed relative motions. In Chen et al (2020) it is proposed to use the non-dimensional parameter C ν to differentiate between gravity-driven mass inflow and other sources of motions (shock compression in Chen et al 2020), with C ν expressed as…”

Section: The Physical Scale Of Dominant Self-gravitymentioning

confidence: 99%

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Formation of the Musca filament: evidence for asymmetries in the accretion flow due to a cloud–cloud collision

Bonne

Bontemps

Schneider

et al. 2020

A&A

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Context. Dense molecular filaments are ubiquituous in the interstellar medium, yet their internal physical conditions and the role of gravity, turbulence, the magnetic field, radiation, and the ambient cloud during their evolution remain debated. Aims. We study the kinematics and physical conditions in the Musca filament, the ambient cloud, and the Chamaeleon-Musca complex to constrain the physics of filament formation. Methods. We produced CO(2–1) isotopologue maps with the APEX telescope that cut through the Musca filament. We further study a NANTEN2 12CO(1–0) map of the full Musca cloud, H I emission of the Chamaeleon-Musca complex, a Planck polarisation map, line radiative transfer models, Gaia data, and synthetic observations from filament formation simulations. Results. The Musca cloud, with a size of ~3–6 pc, contains multiple velocity components. Radiative transfer modelling of the CO emission indicates that the Musca filament consists of a cold (~10 K), dense (nH2 ∼ 104 cm−3) crest, which is best described with a cylindrical geometry. Connected to the crest, a separate gas component at T ~ 15 K and nH2 ∼ 103 cm−3 is found, the so-called strands. The velocity-coherent filament crest has an organised transverse velocity gradient that is linked to the kinematics of the nearby ambient cloud. This velocity gradient has an angle ≥30° with respect to the local magnetic field orientation derived from Planck, and the magnitude of the velocity gradient is similar to the transonic linewidth of the filament crest. Studying the large scale kinematics, we find coherence of the asymmetric kinematics from the 50 pc H I cloud down to the Musca filament. We also report a strong [C18O]/[13CO] abundance drop by an order of magnitude from the filament crest to the strands over a distance <0.2 pc in a weak ambient far-ultraviolet (FUV) field. Conclusions. The dense Musca filament crest is a long-lived (several crossing times), dynamic structure that can form stars in the near future because of continuous mass accretion replenishing the filament. This mass accretion on the filament appears to be triggered by a H I cloud–cloud collision, which bends the magnetic field around dense filaments. This bending of the magnetic field is then responsible for the observed asymmetric accretion scenario of the Musca filament, which is, for instance, seen as a V-shape in the position–velocity (PV) diagram.

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Section: Continuous Mass Accretion On the Filament Crest In Muscasupporting

confidence: 55%

Section: The Physical Scale Of Dominant Self-gravitymentioning

confidence: 99%

Formation of the Musca filament: evidence for asymmetries in the accretion flow due to a cloud–cloud collision

Bonne

Bontemps

Schneider

et al. 2020

A&A

View full text Add to dashboard Cite

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“…For example, studies of Serpens south as well as of IRDC 18223 reveal velocity gradients perpendicular to the clouds in some part of the filaments, but in other parts of the clouds these studies find clearly distinct multiple velocity components that may resemble more the subfilament signatures (Fernández-López et al 2014;Dhabal et al 2018;Beuther et al 2015b). Chen et al (2020) point out that multiple velocity-components along a filament do not necessarily always have to be real structures but that the observational bias that different spectral lines trace different density regimes can also create artificial multiple velocity components in observations (see also Ballesteros-Paredes & Mac Low 2002;Zamora-Avilés et al 2017). Different inclination angles and optical depth effects may also induce a similar bias in some data as well.…”

Section: Gas Dynamicsmentioning

confidence: 95%

“…For example, some regions of low and high mass reveal sub-filaments (or fibers) that may collide and form larger-scale filamentary structures during the formation process (e.g., Hacar et al 2013Hacar et al , 2017bHacar et al , 2018Henshaw et al 2014;Smith et al 2014). Other observations have revealed velocity gradients across filaments (e.g., Palmeirim et al 2013;Fernández-López et al 2014;Beuther et al 2015b;Shimajiri et al 2019) that may be explained by gravity-induced accretion from a magnetized sheet-like molecular cloud (e.g., Chen & Ostriker 2015;Chen et al 2020). However, we should keep in mind that in these clouds, often not just one signature exists but that several signatures occur within the same region.…”

Section: Gas Dynamicsmentioning

confidence: 99%

Fragmentation and kinematics in high-mass star formation

Beuther

Gieser

Suri

et al. 2021

A&A

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Context. The formation of high-mass star-forming regions from their parental gas cloud and the subsequent fragmentation processes lie at the heart of star formation research. Aims. We aim to study the dynamical and fragmentation properties at very early evolutionary stages of high-mass star formation. Methods. Employing the NOrthern Extended Millimeter Array and the IRAM 30 m telescope, we observed two young high-mass star-forming regions, ISOSS22478 and ISOSS23053, in the 1.3 mm continuum and spectral line emission at a high angular resolution (~0.8″). Results. We resolved 29 cores that are mostly located along filament-like structures. Depending on the temperature assumption, these cores follow a mass-size relation of approximately M ∝ r2.0 ± 0.3, corresponding to constant mean column densities. However, with different temperature assumptions, a steeper mass-size relation up to M ∝ r3.0 ± 0.2, which would be more likely to correspond to constant mean volume densities, cannot be ruled out. The correlation of the core masses with their nearest neighbor separations is consistent with thermal Jeans fragmentation. We found hardly any core separations at the spatial resolution limit, indicating that the data resolve the large-scale fragmentation well. Although the kinematics of the two regions appear very different at first sight – multiple velocity components along filaments in ISOSS22478 versus a steep velocity gradient of more than 50 km s−1 pc−1 in ISOSS23053 – the findings can all be explained within the framework of a dynamical cloud collapse scenario. Conclusions. While our data are consistent with a dynamical cloud collapse scenario and subsequent thermal Jeans fragmentation, the importance of additional environmental properties, such as the magnetization of the gas or external shocks triggering converging gas flows, is nonetheless not as well constrained and would require future investigation.

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“…3.3 that differences in the synthetic observations based on LTE and non-LTE calculations are clear even for the basic statistics, such as the power spectra and the intensity PDFs. In the ISM context, the non-LTE effects should be important for a wide range of numerical and observational studies of clouds and cores (Walch et al 2015;Padoan et al 2016;Smith et al 2020), filaments, and velocity-coherent structures (Hacar et al 2013(Hacar et al , 2018Arzoumanian et al 2013;Heigl et al 2020;Chen et al 2020;Clarke et al 2020), and the large-scale velocity fields (Burkhart et al 2014;Hu et al 2020). These problems are inherently 3D in nature, require the coverage of a large dynamical range, and are natural applications of line RT modelling on hierarchical grids.…”

Section: Discussionmentioning

confidence: 99%

LOC program for line radiative transfer

Juvela

2020

A&A

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Context. Radiative transfer (RT) modelling is part of many astrophysical simulations. It is used to make synthetic observations and to assist the analysis of observations. We concentrate on modelling the radio lines emitted by the interstellar medium. In connection with high-resolution models, this can be a significant computationally challenge. Aims. Our aim is to provide a line RT program that makes good use of multi-core central processing units (CPUs) and graphics processing units (GPUs). Parallelisation is essential to speed up computations and to enable large modelling tasks with personal computers. Methods. The program LOC is based on ray-tracing (i.e. not Monte Carlo) and uses standard accelerated lambda iteration (ALI) methods for faster convergence. The program works on 1D and 3D grids. The 1D version makes use of symmetries to speed up the RT calculations. The 3D version works with octree grids, and to enable calculations with large models, is optimised for low memory usage. Results. Tests show that LOC results agree with other RT codes to within ∼2%. This is typical of code-to-code differences, which are often related to different interpretations of the model setup. LOC run times compare favourably especially with those of Monte Carlo codes. In 1D tests, LOC runs were faster by up to a factor ∼20 on a GPU than on a single CPU core. In spite of the complex path calculations, a speed-up of up to ∼10 was also observed for 3D models using octree discretisation. GPUs enable calculations of models with hundreds of millions of cells, as are encountered in the context of large-scale simulations of interstellar clouds. Conclusions. LOC shows good performance and accuracy and and is able to handle many RT modelling tasks on personal computers. It is written in Python, with only the computing-intensive parts implemented as compiled OpenCL kernels. It can therefore also a serve as a platform for further experimentation with alternative RT implementation details.

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Self-gravitating filament formation from shocked flows: velocity gradients across filaments

Cited by 44 publications

References 64 publications

Formation of the Musca filament: evidence for asymmetries in the accretion flow due to a cloud–cloud collision

Formation of the Musca filament: evidence for asymmetries in the accretion flow due to a cloud–cloud collision

Fragmentation and kinematics in high-mass star formation

LOC program for line radiative transfer

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