KFPA Examinations of Young STellar Object Natal Environments (KEYSTONE): Hierarchical Ammonia Structures in Galactic Giant Molecular Clouds

Keown, Jared; Francesco, James Di; Rosolowsky, Erik; Singh, Ayushi; Figura, C.; Kirk, Helen; Chen, Michael Chun-Yuan; Elia, D.; Friesen, Rachel; Ginsburg, Adam; Marston, A. P.; Pezzuto, S.; Schisano, E.; Bontemps, Sylvain; Caselli, P.; Liu, Hongli; Longmore, Steven N.; Motte, F.; Myers, Philip C.; Offner, Stella S. R.; Sanhueza, Patricio; Schneider, N.; Stephens, Ian; Urquhart, J. S.

doi:10.3847/1538-4357/ab3e76

Cited by 27 publications

(20 citation statements)

References 232 publications

(303 reference statements)

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“…We used our Rosette POL-2 data to estimate the polarization angle dispersion. Corresponding molecular line observations of NH 3 (1,1) from the KEYSTONE Survey (Keown et al 2019;J. Di Francesco et al 2021, in preparation) were used for deriving the line widths, and we calculated the H 2 volume density from Herschel-derived masses.…”

Section: Magnetic Field Strength and Stabilitymentioning

confidence: 99%

“…The most suitable molecular line data from which we could estimate the line widths were obtained from the KEYSTONE Survey (Keown et al 2019;J. Di Francesco et al 2021, in preparation), a large project on the 100 m Green Bank Telescope.…”

Section: Magnetic Field Strength and Stabilitymentioning

confidence: 99%

“…This survey is mapping ammonia emission in several giant molecular clouds in order to characterize massive star formation. The spatial resolution of the data cubes is 32″ projected on an 8 8 pixel scale, with a spectral resolution of 0.07 km s −1 (Keown et al 2019).…”

Section: Magnetic Field Strength and Stabilitymentioning

confidence: 99%

“…Background image is our 850 μm Stokes I map, with red contours at 10σ I = 0.13 mJy arcsec −2 . In grayscale the NH 3 (1,1) velocity dispersions are overplotted from the KEYSTONE Survey(Keown et al 2019). In the lower left corner the spatial resolutions of the JCMT 850 μm (∼14″) and the ammonia data (32″) are marked as orange and black circles, respectively.…”

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confidence: 99%

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The JCMT BISTRO-2 Survey: The Magnetic Field in the Center of the Rosette Molecular Cloud

Könyves

Ward-Thompson

Pattle

et al. 2021

ApJ

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We present the first 850 μm polarization observations in the most active star-forming site of the Rosette Molecular Cloud (d ∼ 1.6 kpc) in the wall of the Rosette Nebula, imaged with the SCUBA-2/POL-2 instruments of the James Clerk Maxwell telescope, as part of the B-Fields In Star-forming Region Observations 2 (BISTRO-2) survey. From the POL-2 data we find that the polarization fraction decreases with the 850 μm continuum intensity with α = 0.49 ± 0.08 in the p ∝ I − α relation, which suggests that some fraction of the dust grains remain aligned at high densities. The north of our 850 μm image reveals a "gemstone ring" morphology, which is a ∼1 pc diameter ring-like structure with extended emission in the "head" to the southwest. We hypothesize that it might have been blown by feedback in its interior, while the B-field is parallel to its circumference in most places. In the south of our SCUBA-2 field the clumps are apparently connected with filaments that follow infrared dark clouds. Here, the POL-2 magnetic field orientations appear bimodal with respect to the large-scale Planck field. The mass of our effective mapped area is ∼174 M e , which we calculate from 850 μm flux densities. We compare our results with masses from large-scale emission-subtracted Herschel 250 μm data and find agreement within 30%. We estimate the plane-of-sky B-field strength in one typical subregion using the Davis-Chandrasekhar-Fermi technique and find 80 ± 30 μG toward a clump and its outskirts. The estimated

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Section: Magnetic Field Strength and Stabilitymentioning

confidence: 99%

Section: Magnetic Field Strength and Stabilitymentioning

confidence: 99%

Section: Magnetic Field Strength and Stabilitymentioning

confidence: 99%

mentioning

confidence: 99%

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The JCMT BISTRO-2 Survey: The Magnetic Field in the Center of the Rosette Molecular Cloud

Könyves

Ward-Thompson

Pattle

et al. 2021

ApJ

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“…Large surveys of nearby star-forming regions in NH 3 revealed that the average gas temper-ature in molecular clouds with inactive star formation is around 15 K, while active star-forming cores have temperatures above 20 K (e.g. Urquhart et al 2015;Friesen et al 2017;Hogge et al 2018;Billington et al 2019;Keown et al 2019;Tursun et al 2020). In the range of hydrogen number densities (H 2 ) > ∼ 10 4 cm −3 , the dust and gas temperatures are expected to be well coupled due to frequent collision of dust grains and gas (e.g.…”

Section: Introductionmentioning

confidence: 99%

KAgoshima Galactic Object survey with Nobeyama 45-metre telescope by Mapping in Ammonia lines (KAGONMA): Star formation feedback on dense molecular gas in the W33 complex

Murase,

Handa,

Hirata

et al. 2021

Preprint

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We present the results of NH 3 (1,1), (2,2) and (3,3) and H 2 O maser simultaneous mapping observations toward the high-mass star-forming region W33 with the Nobeyama 45-m radio telescope. W33 has six dust clumps and one of which, W33 Main, is associated with a compact HII region. To investigate star-forming feedback activity on its surroundings, the spatial distribution of the physical parameters was established. The distribution of the rotational temperature shows a systematic change from west to east in our observed region. The hightemperature region obtained in the region near W33 Main is consistent with interaction between the compact HII region and the periphery molecular gas. The size of the interaction area is estimated to be approximately 1.25 pc. NH 3 absorption features are detected toward the centre of the HII region. Interestingly, the absorption feature was detected only in the NH 3 (1,1) and (2,2) transitions, with no absorption feature seen in the (3,3) transition. These complex profiles in NH 3 are difficult to explain by a simple model and may suggest that the gas distribution around the HII region is highly complicated.

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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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KFPA Examinations of Young STellar Object Natal Environments (KEYSTONE): Hierarchical Ammonia Structures in Galactic Giant Molecular Clouds

Cited by 27 publications

References 232 publications

The JCMT BISTRO-2 Survey: The Magnetic Field in the Center of the Rosette Molecular Cloud

The JCMT BISTRO-2 Survey: The Magnetic Field in the Center of the Rosette Molecular Cloud

KAgoshima Galactic Object survey with Nobeyama 45-metre telescope by Mapping in Ammonia lines (KAGONMA): Star formation feedback on dense molecular gas in the W33 complex

Dust polarized emission observations of NGC 6334

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