ALMA reveals the magnetic field evolution in the high-mass star forming complex G9.62+0.19

Abstract

Context. The role of magnetic fields during the formation of high-mass stars is not yet fully understood, and the processes related to the early fragmentation and collapse are largely unexplored today. The high-mass star forming region G9.62+0.19 is a well known source, presenting several cores at different evolutionary stages. Aims. We determine the magnetic field morphology and strength in the high-mass star forming region G9.62+0.19, to investigate its relation to the evolutionary sequence of the cores. Methods. We use Band 7 ALMA observations in full polarisation mode and we analyse the polarised dust emission. We estimate the magnetic field strength via the Davis-Chandrasekhar-Fermi and the Structure Function methods. Results. We resolve several protostellar cores embedded in a bright and dusty filamentary structure. The polarised emission is clearly detected in six regions. Moreover the magnetic field is oriented along the filament and appears perpendicular to the direction of the outflows. We suggest an evolutionary sequence of the magnetic field, and the less evolved hot core exhibits a magnetic field stronger than the more evolved one. We detect linear polarisation from thermal line emission and we tentatively compared linear polarisation vectors from our observations with previous linearly polarised OH masers observations. We also compute the spectral index, the column density and the mass for some of the cores. Conclusions. The high magnetic field strength and the smooth polarised emission indicate that the magnetic field could play an important role for the fragmentation and the collapse process in the star forming region G9.62+019 and that the evolution of the cores can be magnetically regulated. On average, the magnetic field derived by the linear polarised emission from dust, thermal lines and masers is pointing in the same direction and has consistent strength.

accepted by A&A, version after language editing

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• ATOMS: ALMA Three-millimeter Observations of Massive Star-forming regions -- VIII. A search for hot cores by using C${}_2$H${}_5$CN, CH${}_3$OCHO and CH${}_3$OH lines
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• Gravity and rotation drag the magnetic field in high-mass star formation
• Monitoring of the polarized $H_{2}O$ maser emission around the massive protostars W75N(B)-VLA1 and W75N(B)-VLA2
• Multiple molecular outflows and fragmentation in the IRDC core G34.43+00.24 MM1
• Interaction between the Supernova Remnant W44 and the Infrared Dark Cloud G034.77-00.55: shock induced star formation?
• Polarisation of molecular lines in the circumstellar envelope of the post-Asymptotic Giant Branch star OH 17.7-2.0
• Molecular line polarisation from the circumstellar envelopes of Asymptotic Giant Branch stars
• Discs and outflows in the early phases of massive star formation: influence of magnetic fields and ambipolar diffusion
• ATOMS: ALMA Three-millimeter Observations of Massive Star-forming regions -- X. Chemical differentiation among the massive cores in G9.62+0.19