Magnetic Fields in Massive Star-forming Regions (MagMaR). V. The Magnetic Field at the Onset of High-mass Star Formation

Abstract A complete understanding of the initial conditions of high-mass star formation and what processes determine multiplicity requires the study of the magnetic field in young massive cores. Using Atacama Large Millimeter/submillimeter Array (ALMA) 250 GHz polarization observations (0 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mrow> <mml:mi>.</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>″</mml:mi> </mml:mrow> </mml:mover> </mml:math> 3 = 1000 au) and ALMA 220 GHz high-angular-resolution observations (0 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mrow> <mml:mi>.</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>″</mml:mi> </mml:mrow> </mml:mover> </mml:math> 05 = 160 au), we have performed a full energy analysis including the magnetic field at core scales and have assessed what influences the multiplicity inside a massive core previously believed to be in the prestellar phase. With a mass of 31 M ⊙ , the G11.92 MM2 core has a young CS molecular outflow with a dynamical timescale of a few thousand years. At high resolution, the MM2 core fragments into a binary system, with a projected separation of 505 au and a binary mass ratio of 1.14. Using the Davis–Chandrasekhar–Fermi method with an angle dispersion function analysis, we estimate in this core a magnetic field strength of 6.2 mG and a mass-to-magnetic-flux ratio of 18. The MM2 core is strongly subvirialized, with a virial parameter of 0.064, including the magnetic field. The high mass-to-magnetic-flux ratio and low virial parameter indicate that this massive core is very likely undergoing runaway collapse, which is in direct contradiction with the core accretion model. The MM2 core is embedded in a filament that has a velocity gradient consistent with infall. In line with clump-fed scenarios, the core can grow in mass at a rate of 1.9–5.6 × 10 −4 M ⊙ yr −1 . In spite of the magnetic field having only a minor contribution to the total energy budget at core scales (a few thousands of astronomical units), it likely plays a more important role at smaller scales (a few hundreds of astronomical units) by setting the binary properties. Considering energy ratios and a fragmentation criterion at the core scale, the binary system could have been formed by core fragmentation. The binary system properties (projected separation and mass ratio), however, are also consistent with radiation-magnetohydrodynamic simulations with super-Alfvenic or supersonic (or sonic) turbulence that form binaries by disk fragmentation.

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Publication Details

Journal
The Astrophysical Journal
Published
2025-02-05
DOI
https://doi.org/10.3847/1538-4357/ad9d40
Citations
15
Primary Topic
Astrophysics and Star Formation Studies
Type
article
Field-Weighted Citation Impact
17.32

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article

Magnetic Fields in Massive Star-forming Regions (MagMaR). V. The Magnetic Field at the Onset of High-mass Star Formation

Paulo C. Cortés, Eun Jung Chung, Piyali Saha, Jihye Hwang et al.
15 citations
The Astrophysical Journal
Astrophysics and Star Formation Studies
17.32
article

Magnetic Fields in Massive Star-forming Regions (MagMaR). V. The Magnetic Field at the Onset of High-mass Star Formation

Paulo C. Cortés, Eun Jung Chung, Piyali Saha, Jihye Hwang, Patricio Sanhueza, Luis A. Zapata, Suinan Zhang, Shanghuo Li, Fengwei Xu, Ji‐hyun Kang, Yu Cheng, Patrick M. Koch, Huei-Ru Vivien Chen, Janik Karoly, Spandan Choudhury, Adam Ginsburg, Takeshi Sakai, Kaho Morii, C. J. Cyganowski, Wenyu Jiao, Chakali Eswaraiah, Xing Lu, Qiuyi Luo, Kate Pattle, J. M. Girart, B. Commerçon, Fernando A. Olguin, M. T. Beltrán, Ian Stephens, H. Beuther, James M. Jackson, Manuel Fernández-López, Kotomi Taniguchi, A-Ran Lyo, Jia-Wei Wang, Qizhou Zhang, Junhao Liu, Fúmitaka Nakamura
article en
15 citations

Abstract

Abstract A complete understanding of the initial conditions of high-mass star formation and what processes determine multiplicity requires the study of the magnetic field in young massive cores. Using Atacama Large Millimeter/submillimeter Array (ALMA) 250 GHz polarization observations (0 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mrow> <mml:mi>.</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>″</mml:mi> </mml:mrow> </mml:mover> </mml:math> 3 = 1000 au) and ALMA 220 GHz high-angular-resolution observations (0 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mrow> <mml:mi>.</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>″</mml:mi> </mml:mrow> </mml:mover> </mml:math> 05 = 160 au), we have performed a full energy analysis including the magnetic field at core scales and have assessed what influences the multiplicity inside a massive core previously believed to be in the prestellar phase. With a mass of 31 M ⊙ , the G11.92 MM2 core has a young CS molecular outflow with a dynamical timescale of a few thousand years. At high resolution, the MM2 core fragments into a binary system, with a projected separation of 505 au and a binary mass ratio of 1.14. Using the Davis–Chandrasekhar–Fermi method with an angle dispersion function analysis, we estimate in this core a magnetic field strength of 6.2 mG and a mass-to-magnetic-flux ratio of 18. The MM2 core is strongly subvirialized, with a virial parameter of 0.064, including the magnetic field. The high mass-to-magnetic-flux ratio and low virial parameter indicate that this massive core is very likely undergoing runaway collapse, which is in direct contradiction with the core accretion model. The MM2 core is embedded in a filament that has a velocity gradient consistent with infall. In line with clump-fed scenarios, the core can grow in mass at a rate of 1.9–5.6 × 10 −4 M ⊙ yr −1 . In spite of the magnetic field having only a minor contribution to the total energy budget at core scales (a few thousands of astronomical units), it likely plays a more important role at smaller scales (a few hundreds of astronomical units) by setting the binary properties. Considering energy ratios and a fragmentation criterion at the core scale, the binary system could have been formed by core fragmentation. The binary system properties (projected separation and mass ratio), however, are also consistent with radiation-magnetohydrodynamic simulations with super-Alfvenic or supersonic (or sonic) turbulence that form binaries by disk fragmentation.

The Astrophysical JournalVol. 980(1)
National Science Foundation, Natural Science Foundation of Shanghai, National Radio Astronomy Observatory, National Natural Science Foundation of China, Chinese Academy of Sciences, Korea Astronomy and Space Science Institute, National Astronomical Observatory of Japan, Science and Technology Facilities Council, Japan Society for the Promotion of Science, Science and Engineering Research Board, National Institutes of Natural Sciences, Agencia Estatal de Investigación
Openalex Percentile: Top 1%
Astrophysics and Star Formation Studies
17.32
DOIOpen Access PDFOpenAlex
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