Velocity Gradient in the Presence of Self-Gravity: Identifying Gravity-induced Inflow and Determining Collapsing Stage

Hu, Yue; Lazarian, Alex; Yuen, Ka Ho

doi:10.48550/arxiv.2002.06754

Cited by 3 publications

(4 citation statements)

References 51 publications

(78 reference statements)

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“…When one measures the gradients of a highly self-gravitating molecular cloud, they follow the direction of the infall, i.e. the direction of gradients flips 90 • becoming parallel to the magnetic field 46,50 . This happens because the acceleration of the fluid points toward the core of the collapsing region, thus the direction of the magnetic field and of fluid motions induced by gravitational infall become parallel.…”

Section: Gravitational Collapsementioning

confidence: 99%

Magnetic field morphology in interstellar clouds with the velocity gradient technique

Hu¹,

Yuen²,

Lazarian³

et al. 2019

Nat Astron

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Magnetic fields, while ubiquitous in many astrophysical environments, are challenging to measure observationally. Based on the properties of anisotropy of eddies in magnetized turbulence, the Velocity Gradient Technique is a method synergistic to dust polarimetry that is capable of tracing plane-of-the-sky magnetic field, measuring the magnetization of interstellar media and estimating the fraction of gravitational collapsing gas in molecular clouds using spectral line observations. In this paper, we apply this technique to five low-mass star-forming molecular clouds in the Gould Belt and compare the results to the magnetic-field orientation obtained from polarized dust emission. We find the estimates of magnetic field orientations and magnetization for both methods are statistically similar. We estimate the fraction of collapsing gas in the selected clouds. By means of the Velocity Gradient Technique, we also present the plane-of-the-sky magnetic field orientation and magnetization of the Smith cloud, for which dust polarimetry data are unavailable.

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Section: Gravitational Collapsementioning

confidence: 99%

Magnetic field morphology in interstellar clouds with the velocity gradient technique

Hu¹,

Yuen²,

Lazarian³

et al. 2019

Nat Astron

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“…Another particular situation for VGs and IGs is the self-gravity. Hu et al (2020) numerically demonstrated that the inflow induced by gravitational collapse could flip the orientation of both IGs and VGs by 90 degrees, from perpendicular to parallel to the magnetic field. This phenomenon has been observed in the molecular clouds NGC 1333 and Serpens (Hu et al 2019d).…”

Section: Velocity and Intensity Gradient Techniquesmentioning

confidence: 99%

“…According to Hu et al (2020), the relative orientation between the magnetic field as inferred from dust polarimetric observations and the velocity and intensity gradients of the gas emission can be used as an indicator of the undergoing dynamical processes:…”

Section: Coupling Between Magnetic Field Structure and The Cloud's Dy...mentioning

confidence: 99%

Large-scale magnetic field in the Monoceros OB-1 East molecular cloud

Alina,

Montillaud,

et al. 2020

Preprint

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Aims. We study the large-scale magnetic field structure and its interplay with the gas dynamics in the Monoceros OB1 East molecular cloud. Methods. We combine observations of dust polarised emission from the Planck telescope and CO molecular line emission observations from the Taeduk Radio Astronomy Observatory 14-metre telescope. We calculate the strength of the plane-of-the-sky magnetic field using a modified Chandrasekhar-Fermi method and estimate mass over flux ratios in different regions of the cloud. We use the comparison of the velocity and intensity gradients of the molecular line observations with the polarimetric observations to trace dynamically active regions. Results. The molecular complex shows an ordered large-scale plane-of-the-sky magnetic field structure. In the Northern part, it is mostly orientated along the filamentary structures while the Southern part shows at least two regions with distinct magnetic field orientations. We find that in the Northern filaments the magnetic field is unlikely to provide support against fragmentation at large scales. Our analysis reveals a shock region in the Northern part of the complex right in-between two filamentary clouds which were previously suggested to be in collision. Moreover, the shock seems to extend farther towards the Western part of the complex. In the Southern part, we find that either the magnetic field guides the accretion of interstellar matter towards the cloud or it was dragged by the matter towards the densest regions. The large-scale magnetic field in Monoceros OB-1 East molecular clouds is tightly connected to the global structure of the complex and, in the Northern part, it seems to be dominated by gravity and turbulence, while in the Southern part it influences the structuring of matter.

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“…These studies have shown a good correspondence between the magnetic field directions inferred using VGT and that obtained from polarimetry, e.g. with the Planck, BLASTPOL, and HAWC+ data (Hu et al 2019;Alina et al 2022;Hu et al 2020Hu et al , 2021. The property of intensity gradients being related to magnetic field direction has also been used in the developments of Koch et al (2012) to infer magnetic field direction in molecular clouds.…”

Section: Introductionmentioning

confidence: 68%

Unveiling polarized emission from interstellar dust of the Large Magellanic Cloud with Planck

Alina¹,

Bernard²,

Yuen³

et al. 2022

Preprint

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Polarization of interstellar dust emission is a powerful probe of dust properties and magnetic field structure. Yet studies of external galaxies are hampered by foreground dust contribution. The aim of this study is to separate the polarised signal from the Large Magellanic Cloud (LMC) from that of the Milky Way (MW) in order to construct a wide-field, spatially complete map of dust polarization using the Planck 353 GHz data. To estimate the foreground polarization direction, we used velocity gradients in HI spectral line data and assessed the performance of the output by comparing to starlight extinction polarization. We estimate the foreground intensity using dust properties derived previously from the Planck data and we assume the foreground polarization to be uniform and equal to the average of the MW around the galaxy.After foreground removal, the geometry of the plane-of-the-sky magnetic field in the LMC tends to follow the structure of the atomic gas in the LMC. This is notably the case along the molecular ridges extending south and south-east of the 30 Doradus star-forming complex, and along more diffuse southern arm extending towards the Small Magellanic Cloud. There is also an alignment between the magnetic field and the outer arm in the western part. The median polarization fraction in the LMC is slightly lower than that observed for the MW while the anti-correlation between the polarization angle dispersion function and the polarization fraction is slightly larger. Overall, polarization fraction distribution is similar to that observed in the MW.

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Velocity Gradient in the Presence of Self-Gravity: Identifying Gravity-induced Inflow and Determining Collapsing Stage

Cited by 3 publications

References 51 publications

Magnetic field morphology in interstellar clouds with the velocity gradient technique

Magnetic field morphology in interstellar clouds with the velocity gradient technique

Large-scale magnetic field in the Monoceros OB-1 East molecular cloud

Unveiling polarized emission from interstellar dust of the Large Magellanic Cloud with Planck

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