Magnetized Converging Flows toward the Hot Core in the Intermediate/High-mass Star-forming Region NGC 6334 V

Juárez, Carmen; Girart, J. M.; Zamora-Avilés, Manuel; Tang, Ya-Wen; Koch, Patrick M.; Liu, Hauyu Baobab; Palau, Aina; Ballesteros-Paredes, Javier; Zhang, Qizhou; Qiu, Keping

doi:10.3847/1538-4357/aa78a6

Cited by 30 publications

(43 citation statements)

References 85 publications

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“…In addition to analyzing the effect of different telescope resolutions Frontiers (their conclusion: lower-resolution observations tend to overestimate the field strength), they also derived a generalized form of the DCF equation, which allows for the separation of the turbulent and mean magnetic field components, and yielded magnetic-field estimates that were accurate to within ∼ 20%. More recently, Juárez et al (2017) performed SMA observations of a magnetized high-mass star-forming region and used the structure-function method to compare the data with synthetic observations of gravity-dominated MHD simulations. They found the magnetic field strength estimates from both the observations and simulations to be in good agreement.…”

Section: Indirect Estimates Of Magnetic Field Strengthmentioning

confidence: 99%

“…To date, there are approximately 24 unique high-mass star forming clumps that have been observed in polarization with interferometers. They are Orion KL, NGC 2071, W3, W3(OH), DR 21(OH), DR 21 filament, G192, G30.79, NGC 6334 I/In/IV/V, W51 e and N, IRAS 18306, IRAS 18089, W43, NGC 7538, G5.89, NGC 2264C1, G34.4, G35.2N, G31.41+0.31, and G240.31+0.07 (Rao et al, 1998;Lai et al, 2001Lai et al, , 2003Cortes et al, , 2008Girart et al, 2009;Tang et al, 2009a,b;Beuther et al, 2010;Tang et al, 2010;Chen et al, 2012;Girart et al, 2013;Liu et al, 2013;Qiu et al, 2013;Frau et al, 2014;Hull et al, 2014;Qiu et al, 2014;Sridharan et al, 2014;Wright et al, 2014;Zhang et al, 2014;Li et al, 2015;Cortes et al, 2016;Houde et al, 2016;Ching et al, 2017;Juárez et al, 2017;Koch et al, 2018) Magnetic fields toward these sources display diverse topologies. In Sections 3.2, 3.3, 3.4, and 4 we discuss findings and interesting trends from the statistical analysis of this sample.…”

Section: Magnetic Field Measurements At Core Scalesmentioning

confidence: 99%

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Interferometric Observations of Magnetic Fields in Forming Stars

Hull

Zhang

2019

Front. Astron. Space Sci.

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114

103

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The magnetic field is a key ingredient in the recipe of star formation. However, the importance of the magnetic field in the early stages of the formation of low-and high-mass stars is still far from certain. Over the past two decades, the millimeter and submillimeter interferometers BIMA, OVRO, CARMA, SMA, and most recently ALMA have made major strides in unveiling the role of the magnetic field in star formation at progressively smaller spatial scales; ALMA observations have recently achieved spatial resolutions of up to ∼ 100 au and ∼ 1,000 au in nearby low-and high-mass star-forming regions, respectively. From the kiloparsec scale of molecular clouds down to the inner few hundred au immediately surrounding forming stars, the polarization at millimeter and submillimeter wavelengths is dominated by polarized thermal dust emission, where the dust grains are aligned relative to the magnetic field. Interferometric studies have focused on this dust polarization and occasionally on the polarization of spectral-line emission. We review the current state of the field of magnetized star formation, from the first BIMA results through the latest ALMA observations, in the context of several questions that continue to motivate the studies of highand low-mass star formation. By aggregating and analyzing the results from individual studies, we come to several conclusions: (1) Magnetic fields and outflows from low-mass protostellar cores are randomly aligned, suggesting that the magnetic field at ∼ 1000 au scales is not the dominant factor in setting the angular momentum of embedded disks and outflows. (2) Recent measurements of the thermal and dynamic properties in high-mass star-forming regions reveal small virial parameters, challenging the assumption of equilibrium star formation. However, we estimate that a magnetic field strength of a fraction of a mG to several mG in these objects could bring the dense gas close to a state of equilibrium. Finally, (3) We find that the small number of sources with hourglass-shaped magnetic field morphologies at 0.01-0.1 pc scales cannot be explained purely by projection effects, suggesting that while it does occur occasionally, magnetically dominated core collapse is not the predominant mode of low-or high-mass star formation. Magnetic fields in forming stars Polarized molecular-line emissionPolarization of molecular-line emission is another tracer of the magnetic field in star-forming regions. Molecular and atomic lines are sensitive to magnetic fields, which cause their spectral levels to split into magnetic sub-levels. For some molecules, linear polarization can arise when an anisotropy in the radiation and/or velocity field yields a population of magnetic sub-levels that are not in local thermodynamic equilibrium (LTE); this is known as the Goldreich-Kylafis (G-K) effect. Polarization from the G-K effect is most easily detected where the spectral line emission has an optical depth τ ≈ 1, when the ratio of the collision rate to the radiative transition rate (i.e., the spontaneous emi...

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Section: Indirect Estimates Of Magnetic Field Strengthmentioning

confidence: 99%

Section: Magnetic Field Measurements At Core Scalesmentioning

confidence: 99%

Interferometric Observations of Magnetic Fields in Forming Stars

Hull

Zhang

2019

Front. Astron. Space Sci.

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114

103

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“…The magnetic field structure of NGC 6334 has been investigated at large scales (∼10 pc) using starlight polarization and at small scales ( 0.1 pc) towards the dense cores using interferometric observations of dust polarized emission with the SMA (Li et al 2006;Zhang et al 2014;Li et al 2015;Juárez et al 2017). By combining and interpolating some of the latter measurements, Li et al (2015) suggested that the orientation of the B-field does not change significantly over the various scales, pointing to the important dynamical role played by the B-field in the formation of NGC 6334.…”

Section: Introductionmentioning

confidence: 99%

Dust polarized emission observations of NGC 6334

Arzoumanian¹,

Furuya²,

Hasegawa³

et al. 2021

A&A

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Context. Molecular filaments and hubs have received special attention recently thanks to new studies showing their key role in star formation. While the (column) density and velocity structures of both filaments and hubs have been carefully studied, their magnetic field (B-field) properties have yet to be characterized. Consequently, the role of B-fields in the formation and evolution of hub-filament systems is not well constrained. Aims. We aim to understand the role of the B-field and its interplay with turbulence and gravity in the dynamical evolution of the NGC 6334 filament network that harbours cluster-forming hubs and high-mass star formation. Methods. We present new observations of the dust polarized emission at 850 μm toward the 2 pc × 10 pc map of NGC 6334 at a spatial resolution of 0.09 pc obtained with the James Clerk Maxwell Telescope (JCMT) as part of the B-field In STar-forming Region Observations (BISTRO) survey. We study the distribution and dispersion of the polarized intensity (PI), the polarization fraction (PF), and the plane-of-the-sky B-field angle (χB_POS) toward the whole region, along the 10 pc-long ridge and along the sub-filaments connected to the ridge and the hubs. We derived the power spectra of the intensity and χBPOS along the ridge crest and compared them with the results obtained from simulated filaments. Results. The observations span ~3 orders of magnitude in Stokes I and PI and ~2 orders of magnitude in PF (from ~0.2 to ~ 20%). A large scatter in PI and PF is observed for a given value of I. Our analyses show a complex B-field structure when observed over the whole region (~ 10 pc); however, at smaller scales (~1 pc), χBPOS varies coherently along the crests of the filament network. The observed power spectrum of χBPOS can be well represented with a power law function with a slope of − 1.33 ± 0.23, which is ~20% shallower than that of I. We find that this result is compatible with the properties of simulated filaments and may indicate the physical processes at play in the formation and evolution of star-forming filaments. Along the sub-filaments, χBPOS rotates frombeing mostly perpendicular or randomly oriented with respect to the crests to mostly parallel as the sub-filaments merge with the ridge and hubs. This variation of the B-field structure along the sub-filaments may be tracing local velocity flows of infalling matter in the ridge and hubs. Our analysis also suggests a variation in the energy balance along the crests of these sub-filaments, from magnetically critical or supercritical at their far ends to magnetically subcritical near the ridge and hubs. We also detect an increase in PF toward the high-column density (NH2 ≳ 1023 cm−2) star cluster-forming hubs. These latter large PF values may be explained by the increase in grain alignment efficiency due to stellar radiation from the newborn stars, combined with an ordered B-field structure. Conclusions. These observational results reveal for the first time the characteristics of the small-scale (down to ~ 0.1 pc) B-field structure of a 10 pc-long hub-filament system. Our analyses show variations in the polarization properties along the sub-filaments that may be tracing the evolution of their physical properties during their interaction with the ridge and hubs. We also detect an impact of feedback from young high-mass stars on the local B-field structure and the polarization properties, which could put constraints on possible models for dust grain alignment and provide important hints as to the interplay between the star formation activity and interstellar B-fields.

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“…Multiple IR, cm and mm sources are found at the flow interface as well (Figs. 1 and 4 of Juárez et al 2017). Overall, the similarities of NGC 6334 V and ISOSS J23053+5953 are remarkable, in spite of clearly being located in different parts of the Galaxy.…”

Section: Dynamics In Isoss J23053+5953mentioning

confidence: 84%

“…For example, in the well known giant molecular cloud complex NGC 6334, colliding flows have been reported in the source known as "V" by Juárez et al (2017), where two velocity components separated about 2.4 km s −1 are seen in H 13 CO + , with SiO emission at the intermediate velocities and also at the interface of the two flows (Fig. 7 of Juárez et al 2017). Multiple IR, cm and mm sources are found at the flow interface as well (Figs.…”

Section: Dynamics In Isoss J23053+5953mentioning

confidence: 99%

Clustered star formation at early evolutionary stages

Gieser

Beuther

Semenov

et al. 2021

A&A

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Context. The process of high-mass star formation during the earliest evolutionary stages and the change over time of the physical and chemical properties of individual fragmented cores are still not fully understood. Aims. We aim to characterize the physical and chemical properties of fragmented cores during the earliest evolutionary stages in the very young star-forming regions ISOSS J22478+6357 and ISOSS J23053+5953. Methods. NOrthern Extended Millimeter Array (NOEMA) 1.3 mm data are used in combination with archival mid-and far-infrared Spitzer and Herschel telescope observations to construct and fit the spectral energy distributions (SEDs) of individual fragmented cores. The radial density profiles are inferred from the 1.3 mm continuum visibility profiles and the radial temperature profiles are estimated from H 2 CO rotation temperature maps. Molecular column densities are derived with the line fitting tool XCLASS. The physical and chemical properties are combined by applying the physical-chemical model MUSCLE in order to constrain the chemical timescales of a few line-rich cores. The morphology and spatial correlations of the molecular emission are analyzed using the histogram of oriented gradients (HOG) method.Results. The mid-infrared data show that both regions contain a cluster of young stellar objects. Bipolar molecular outflows are observed in the CO 2 − 1 transition toward the strong mm cores indicating protostellar activity. We find strong molecular emission of SO, SiO, H 2 CO, and CH 3 OH in locations which are not associated with the mm cores. These shocked knots can be either associated with the bipolar outflows or, in the case of ISOSS J23053+5953, with a colliding flow that creates a large shocked region between the mm cores. The mean chemical timescale of the cores is lower (∼20 000 yr) compared to that of the sources of the more evolved CORE sample (∼60 000 yr). With the HOG method, we find that the spatial emission of species tracing the extended emission and of shock-tracing molecules are well correlated within transitions of these groups. Conclusions. Clustered star formation is observed toward both regions. Comparing the mean results of the density and temperature power-law index with the results of the original CORE sample of more evolved regions (Gieser et al. 2021), it appears that both do not change significantly from the earliest evolutionary stages to the hot molecular core stage. However, we find that the 1.3 mm flux, kinetic temperature, H 2 column density, and core mass of the cores increase in time, which can be traced both in the M/L ratio and the chemical timescale τ chem .

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Magnetized Converging Flows toward the Hot Core in the Intermediate/High-mass Star-forming Region NGC 6334 V

Cited by 30 publications

References 85 publications

Interferometric Observations of Magnetic Fields in Forming Stars

Interferometric Observations of Magnetic Fields in Forming Stars

Dust polarized emission observations of NGC 6334

Clustered star formation at early evolutionary stages

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