Junhao Liu

East Asian Observatory

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Keping Qiu

Nanjing University

Patrick M. Koch

Institute of Astronomy and Astrophysics, Academia Sinica

Huei-Ru Vivien Chen

National Tsing Hua University

Tao-Chung Ching

National Radio Astronomy Observatory

Ramprasad Rao

Center for Astrophysics Harvard & Smithsonian

Tie Liu

Shanghai Astronomical Observatory

Eun Jung Chung

Chungnam National University

Ya‐Wen Tang

Institute of Astronomy and Astrophysics, Academia Sinica

Kate Pattle

University College London

Jia-Wei Wang

Southeast University

Cooperative Institutions

Chinese Academy of Sciences

Max Planck Society

Institute of Astronomy and Astrophysics, Academia Sinica

Korea Astronomy and Space Science Institute

National Astronomical Observatory of Japan

East Asian Observatory

Centre National de la Recherche Scientifique

Center for Astrophysics Harvard & Smithsonian

Max Planck Institute for Radio Astronomy

University of Chinese Academy of Sciences

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The JCMT BISTRO Survey: The Magnetic Fields of the IC 348 Star-forming Region

arXiv (Cornell University) (2024)

Youngwoo Choi Woojin Kwon Kate Pattle D. Arzoumanian Tyler L. Bourke

We present 850 $\mu$m polarization observations of the IC 348 star-forming region in the Perseus molecular cloud as part of the B-fields In STar-forming Region Observation (BISTRO) survey. We study the magnetic properties of two cores (HH 211 MMS and IC 348 MMS) and a filamentary structure of IC 348. We find that the overall field tends to be more perpendicular than parallel to the filamentary structure of the region. The polarization fraction decreases with intensity, and we estimate the trend by power-law and the mean of the Rice distribution fittings. The power indices for the cores are much smaller than 1, indicative of possible grain growth to micron size in the cores. We also measure the magnetic field strengths of the two cores and the filamentary area separately by applying the Davis-Chandrasekhar-Fermi method and its alternative version for compressed medium. The estimated mass-to-flux ratios are 0.45-2.20 and 0.63-2.76 for HH 211 MMS and IC 348 MMS, respectively, while the ratios for the filament is 0.33-1.50. This result may suggest that the transition from subcritical to supercritical conditions occurs at the core scale ($\sim$ 0.05 pc) in the region. In addition, we study the energy balance of the cores and find that the relative strength of turbulence to the magnetic field tends to be stronger for IC 348 MMS than HH 211 MMS. The result could potentially explain the different configurations inside the two cores: a single protostellar system in HH 211 MMS and multiple protostars in IC 348 MMS.

Star (game theory)

10.48550/arxiv.2411.01960

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Contents

Journal of the Ceramic Society of Japan (2016)

Junhao Liu G. Zhang Kuo–Chih Chou Bing-Jing Li Samuel Y.‐S. Wang

Characterization and catalytic behavior of cerium oxide doped into aluminosilicophosphate glasses

10.2109/jcersj2.124.c2-1

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Prognostic Value of Plasma Big Endothelin-1 Level among Patients with Three-Vessel Disease: A Cohort Study

Journal of Atherosclerosis and Thrombosis (2019)

Ce Zhang Jian Tian Lin Jiang Lianjun Xu Junhao Liu

To evaluate the prognostic value of plasma big endothelin-1 level in the context of three-vessel disease (TVD) with heavy atherosclerotic burden.

Plasma levels

Value (mathematics)

10.5551/jat.47324

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DR 21 South Filament: A Parsec-sized Dense Gas Accretion Flow onto the DR 21 Massive Young Cluster

The Astrophysical Journal (2021)

Bo Hu Keping Qiu Yue Cao Junhao Liu Yuwei Wang

DR21 south filament (DR21SF) is a unique component of the giant network of filamentary molecular clouds in the north region of Cygnus X complex. Unlike the highly fragmented and star-forming active environment it resides, DR21SF exhibits a coherent profile in the column density map with very few star formation signposts, even though the previously reported linear density of the filament is an order of magnitude higher than the thermal stable threshold. We derive the size (3.6~pc by 0.13~pc), temperature (10 to 15~K), and mass (1048~\textit{M$_\odot$}) of DR21SF from Shanghai 65 m TianMa Radio Telescope (TMRT) observations of NH$_3$ (1, 1) and (2, 2) inversion lines in conjunction with the column density map from our previous work. Star-forming sites are identified along the filament where gas temperature excesses. We find clear gradients in radial velocity and intrinsic line-width along the spine of the filament. The gradients can be well interpreted with a scenario of an accretion flow feeding DR 21 at a mass transfer rate of $1.1 \times 10^{-3}$~\textit{M$_\odot$} yr$^{-1}$. Based on the analysis of its kinematic temperature, intrinsic line-width and mass distribution, we conclude that DR21SF is in an overall trans-critical status, which indicates an early evolutionary stage.

Line (geometry)

10.3847/1538-4357/abd03a

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Development of 230 GHz finline SIS mixers for next-generation large array receivers and HARP instrument upgrade

Kuan‐Yu Liu Boon-Kok Tan Ming-Jye Wang P. Kittara Dan Singwong

Upgrade

10.1117/12.3018151

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Magnetic field segments derived from JCMT/POL2 850 micrion polarization observations toward the Central Molecular Zone

Zenodo (CERN European Organization for Nuclear Research) (2023)

Xing Lu Junhao Liu

Catalogs of magnetic field segments derived from JCMT/POL2 850 micrion polarization observations toward the Central Molecular Zone (Lu et al. 2023, ApJ accepted, https://ui.adsabs.harvard.edu/abs/2023arXiv231201776L/abstract). The position angles are those of the magnetic field (i.e., polarization position angles rotated by 90 degree). The files 'CLOUDNAME_cloud_tran.mrt' are field segments within the boundaries of the clouds (see Figure 2 in the reference paper). Here 'CLOUDNAME' is one of the eleven clouds defined in the paper, including: 50kms, brick, CO002, DRb, DRc, DRd, DRef, fsc, sgrc, stone, and strawsticks. The files 'REGIONNAME_bin2_pdp3_deg.mrt' are field segments in the three large tiles, regardless of whether the segments are within a cloud or not (see the dashed magenta boxes in Figure 1 in the reference paper). Here 'REGIONNAME' is one of the three large tiles, i.e., dustridge, gc, and sgrcaround. Please check the Byte-by-byte Description inside the files for the meanings of the columns in the tables. Many thanks to August Muench for converting the files to machine readable tables.

10.5281/zenodo.10294715

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The JCMT BISTRO Survey: A Spiral Magnetic Field in a Hub-filament Structure, Monoceros R2

The Astrophysical Journal (2022)

Jihye Hwang Jongsoo Kim Kate Pattle Chang Won Lee Patrick M. Koch

We present and analyze observations of polarized dust emission at 850 $\mu$m towards the central 1 pc $\times$ 1 pc hub-filament structure of Monoceros R2 (Mon R2). The data are obtained with SCUBA-2/POL-2 on the James Clerk Maxwell Telescope (JCMT) as part of the BISTRO (B-fields in Star-forming Region Observations) survey. The orientations of the magnetic field follow the spiral structure of Mon R2, which are well-described by an axisymmetric magnetic field model. We estimate the turbulent component of the magnetic field using the angle difference between our observations and the best-fit model of the underlying large-scale mean magnetic field. This estimate is used to calculate the magnetic field strength using the Davis-Chandrasekhar-Fermi method, for which we also obtain the distribution of volume density and velocity dispersion using a column density map derived from $Herschel$ data and the C$^{18}$O ($J$ = 3-2) data taken with HARP on the JCMT, respectively. We make maps of magnetic field strengths and mass-to-flux ratios, finding that magnetic field strengths vary from 0.02 to 3.64 mG with a mean value of 1.0 $\pm$ 0.06 mG, and the mean critical mass-to-flux ratio is 0.47 $\pm$ 0.02. Additionally, the mean Alfv\'en Mach number is 0.35 $\pm$ 0.01. This suggests that in Mon R2, magnetic fields provide resistance against large-scale gravitational collapse, and magnetic pressure exceeds turbulent pressure. We also investigate the properties of each filament in Mon R2. Most of the filaments are aligned along the magnetic field direction and are magnetically sub-critical.

10.3847/1538-4357/ac99e0

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Citations (14)

MagMar III -- Resisting the Pressure, Is the Magnetic Field Overwhelmed in NGC6334I?

arXiv (Cornell University) (2024)

Paulo C. Cortés J. M. Girart Patricio Sanhueza Junhao Liu S. Martín

We report on ALMA observations of polarized dust emission at 1.2 mm from NGC6334I, a source known for its significant flux outbursts. Between five months, our data show no substantial change in total intensity and a modest 8\% variation in linear polarization, suggesting a phase of stability or the conclusion of the outburst. The magnetic field, inferred from this polarized emission, displays a predominantly radial pattern from North-West to South-East with intricate disturbances across major cores, hinting at spiral structures. Energy analysis of CS$(J=5 \rightarrow 4)$ emission yields an outflow energy of approximately $3.5\times10^{45}$ ergs, aligning with previous interferometric studies. Utilizing the Davis-Chandrasekhar-Fermi method, we determined magnetic field strengths ranging from 1 to 11 mG, averaging at 1.9 mG. This average increases to 4 $\pm 1$ mG when incorporating Zeeman measurements. Comparative analyses using gravitational, thermal, and kinetic energy maps reveal that magnetic energy is significantly weaker, possibly explaining the observed field morphology. We also find that the energy in the outflows and the expanding cometary {\HII} region is also larger than the magnetic energy, suggesting that protostellar feedback maybe the dominant driver behind the injection of turbulence in NGC6334I at the scales sampled by our data. The gas in NGC6334I predominantly exhibits supersonic and trans-Alfvenic conditions, transitioning towards a super-Alfvenic regime, underscoring a diminished influence of the magnetic field with increasing gas density. These observations are in agreement with prior polarization studies at 220 GHz, enriching our understanding of the dynamic processes in high-mass star-forming regions.

10.48550/arxiv.2406.14663

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Surveys of Clumps, Cores, and Condensations in Cygnus X. II. Radio Properties of Massive Dense Cores

The Astrophysical Journal (2022)

Yuwei Wang Keping Qiu Yue Cao Yu Cheng Junhao Liu

We have carried out a high-sensitivity and high-resolution radio continuum study towards a sample of 47 massive dense cores (MDCs) in the Cygnus X star-forming complex using the Karl G. Jansky Very Large Array, aiming to detect and characterize the radio emission associated with star-forming activities down to ~0.01 pc scales. We have detected 64 radio sources within or closely around the full width at half-maximum (FWHM) of the MDCs, of which 37 are reported for the first time. The majority of the detected radio sources are associated with dust condensations embedded within the MDCs, and they are mostly weak and compact. We are able to build spectral energy distributions for 8 sources. Two of them indicate non-thermal emission and the other six indicate thermal free-free emission. We have determined that most of the radio sources are ionized jets or winds originating from massive young stellar objects, whereas only a few sources are likely to be ultra-compact HII regions. Further quantitative analyses indicate that the radio luminosity of the detected radio sources increases along the evolution path of the MDCs.

Jansky

10.3847/1538-4357/ac480a

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Calibrating the Davis-Chandrasekhar-Fermi method with numerical simulations: uncertainties in estimating the magnetic field strength from statistics of field orientations.

arXiv (Cornell University) (2021)

Junhao Liu Qizhou Zhang B. Commerçon Valeska Valdivia A. Maury

The Davis-Chandrasekhar-Fermi (DCF) method is widely used to indirectly estimate the magnetic field strength from the plane-of-sky field orientation. In this work, we present a set of 3D MHD simulations and synthetic polarization images using radiative transfer of clustered massive star-forming regions. We apply the DCF method on the synthetic polarization maps to investigate its reliability in high-density molecular clumps and dense cores where self-gravity is significant. We investigate the validity of the assumptions of the DCF method step by step and compare the model and estimated field strength to derive the correction factors for the estimated uniform and total (rms) magnetic field strength at clump and core scales. The correction factors in different situations are catalogued. We find the DCF method works well in strong field cases. However, the magnetic field strength in weak field cases could be significantly overestimated by the DCF method when the turbulent magnetic energy is smaller than the turbulent kinetic energy. We investigate the accuracy of the angular dispersion function (ADF, a modified DCF method) method on the effects that may affect the measured angular dispersion and find that the ADF method correctly accounts for the ordered field structure, the beam-smoothing, and the interferometric filtering, but may not be applicable to account for the signal integration along the line of sight in most cases. Our results suggest that the DCF methods should be avoided to be applied below $\sim$0.1 pc scales if the effect of line-of-sight signal integration is not properly addressed.

Field strength

Chandrasekhar limit

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