Oscillating Filaments. I. Oscillation and Geometrical Fragmentation

Gritschneder, Matthias; Heigl, Stefan; Burkert, Andreas

doi:10.3847/1538-4357/834/2/202

Cited by 30 publications

(23 citation statements)

References 29 publications

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“…6 and 7). Using numerical simulations, Gritschneder et al (2017) investigated the fragmentation properties of filaments including sinusoidal bends or longitudinal oscillations and they show that bending filaments are prone to "geometrical fragmentation", a process that generates cores at the turning points of the geometrical oscillation, which are separated by half the wavelength of the initial sinusoidal perturbation. This process may be partly at work here.…”

Section: Fragmentation Manner Of Filaments 8 and 10mentioning

confidence: 99%

Fragmentation of star-forming filaments in the X-shaped nebula of the California molecular cloud

Zhang

André

Wang

2020

A&A

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Context. Dense molecular filaments are central to the star formation process, but the detailed manner in which they fragment into prestellar cores is not well understood yet. Aims. Here, we investigate the fragmentation properties and dynamical state of several star-forming filaments in the X-shaped nebula region of the California molecular cloud in an effort to shed some light on this issue. Methods. We used multiwavelength far-infrared images from Herschel as well as the getsources and getfilaments extraction methods to identify dense cores and filaments in the region and derive their basic properties. We also used a map of 13CO(2−1) emission from the Arizona 10m Submillimeter Telescope (SMT) to constrain the dynamical state of the filaments. Results. We identified ten filaments with aspect ratios of AR > 4 and column density contrasts of C > 0.5, as well as 57 dense cores, including two protostellar cores, 20 robust prestellar cores, 11 candidate prestellar cores, and 24 unbound starless cores. All ten filaments have roughly the same deconvolved full width at half maximum (FWHM), with a median value of 0.12 ± 0.03 pc, which is independent of their column densities ranging from <1021 cm−2 to >1022 cm−2. Two star-forming filaments (# 8 and # 10) stand out since they harbor quasi-periodic chains of dense cores with a typical projected core spacing of ~0.15 pc. These two filaments have thermally supercritical line masses and are not static. Filament 8 exhibits a prominent transverse velocity gradient, suggesting that it is accreting gas from the parent cloud gas reservoir at an estimated rate of ~40 ± 10 M⊙ Myr−1 pc−1. Filament 10 includes two embedded protostars with outflows and it is likely at a somewhat later evolutionary stage than filament 8. In both cases, the observed (projected) core spacing is similar to the filament width and significantly shorter than the canonical separation of ~4 times the filament width predicted by classical cylinder fragmentation theory. It is unlikely that projection effects can explain this discrepancy. We suggest that the continuous accretion of gas onto the two star-forming filaments, as well as the geometrical bending of the filaments, may account for the observed core spacing. Conclusions. Our findings suggest that the characteristic fragmentation lengthscale of molecular filaments is quite sensitive to external perturbations from the parent cloud, such as the gravitational accretion of ambient material.

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Section: Fragmentation Manner Of Filaments 8 and 10mentioning

confidence: 99%

Fragmentation of star-forming filaments in the X-shaped nebula of the California molecular cloud

Zhang

André

Wang

2020

A&A

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“…3 and 4). Using numerical simulations, Gritschneder et al (2017) investigated the fragmentation properties of filaments including sinusoidal bends or longitudi-Guo-Yin Zhang et al: Fragmentation of star-forming filaments in the X-shape Nebula of the California molecular cloud nal oscillations and showed that bending filaments are prone to "geometrical fragmentation", a process which generates cores at the turning points of the geometrical oscillation, separated by half the wavelength of the initial sinusoidal perturbation. Such a process may be partly at work here, although the geometrical deformations observed in filaments 8 and 10 (compared to straight filaments) are not purely sinusoidal, and some of the detected cores are apparently not located at clear bends along the filaments (cf.…”

Section: Fragmentation Manner Of Filaments 8 and 10mentioning

confidence: 99%

Fragmentation of star-forming filaments in the X-shape Nebula of the California molecular cloud

Zhang,

Andre,

Menshchikov

et al. 2020

Preprint

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Aims. We aim to further investigate the fragmentation of star-forming filaments in the X-shape Nebula of the California molecular cloud, so as to better understand the exact role of filaments in the early stages of star formation. Methods. We applied getsources and getfilaments extraction methods to the multi-wavelength images observed with Herschel in order to produce background-subtracted images of candidate cores and filaments, respectively. The properties of the filaments and cores were determined from such an analysis. A map of 13 CO(2 − 1) emission from the SMT 10m telescope was also used to constrain the dynamical state of the filaments. Results. We obtained a complete sample of filamentary structures and dense cores from the Herschel high-resolution (18.2 ) H 2 column density map of the region. We selected 10 filaments with elongation factors E > 4 and column density contrasts C > 0.5 from the filamentary network identified with getfilaments. All 10 filaments have roughly the same deconvolved FWHM width, with a median value 0.12 ± 0.03 pc, independently of their column densities ranging from < 10 21 cm −2 to > 10 22 cm −2 . We also identified 2 protostellar cores, 20 robust prestellar cores, 11 candidate prestellar cores, and 27 unbound starless cores. Two star-forming filaments stand out based on the Herschel data: Filaments 8 and 10 harbor quasi-periodic chains of dense cores with a typical projected core spacing of ∼ 0.15 pc. These two filamentary structures have supercritical line masses and are not static. Filament 8 exhibits a prominent transverse velocity gradient, suggesting that it is accreting gas from the parent cloud gas reservoir. The estimated mass accretion rate is ∼ 40 ± 10 M Myr −1 pc −1 . Filament 10 includes two embedded protostars with outflows and is likely at a later evolutionary stage than filament 8. Our findings support the notion that dense molecular filaments play a crucial role in the star formation process. We suggest that accretion onto the two star-forming filaments, as well as geometrical bending, explains why the observed core spacing along them is significantly shorter than the canonical separation of ∼ 4 times the filament width predicted by classical cylinder fragmentation theory.

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“…Moreover, due to the Herschel dust observations (André et al 2010(André et al , 2014Arzoumanian et al 2019) combined with ground based molecular line observations (Hacar & Tafalla 2011;Kainulainen et al 2016;Yuan et al 2020) a much broader picture could be manifested in the last years. For example, most prestellar cores are found in supercritical filaments (Könyves et al 2015;André et al 2010) despite the fact that cores could also form by fragmentation of subcritical structures (Nagasawa 1987;Fischera & Martin 2012;Heigl et al 2016;Gritschneder et al 2017;Chira et al 2018).…”

Section: Introductionmentioning

confidence: 99%

Merging Filaments I: A race against collapse

Hoemann,

Heigl,

Burkert

2021

Preprint

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The interstellar medium is characterised by an intricate filamentary network which exhibits complex structures. These show a variety of different shapes (e. g. junctions, rings, etc.) deviating strongly from the usually assumed cylindrical shape. A possible formation mechanism are filament mergers which we analyse in this study. Indeed, the proximity of filaments in networks suggests mergers to be rather likely. As the merger has to be faster than the end dominated collapse of the filament along its major axis we expect three possible results: (a) The filaments collapse before a merger can happen, (b) the merged filamentary complex shows already signs of cores at the edges or (c) the filaments merge into a structure which is not end-dominated. We develop an analytic formula for the merging and core-formation timescale at the edge and validate our model via hydrodynamical simulations with the adaptive-mesh-refinement-code RAMSES. This allows us to predict the outcome of a filament merger, given different initial conditions which are the initial distance and the respective line-masses of each filament as well as their relative velocities.

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Oscillating Filaments. I. Oscillation and Geometrical Fragmentation

Cited by 30 publications

References 29 publications

Fragmentation of star-forming filaments in the X-shaped nebula of the California molecular cloud

Fragmentation of star-forming filaments in the X-shaped nebula of the California molecular cloud

Fragmentation of star-forming filaments in the X-shape Nebula of the California molecular cloud

Merging Filaments I: A race against collapse

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