Outflows, cores and magnetic field orientations in W43-MM1 as seen by ALMA

Abstract

It has been proposed that the magnetic field, pervasive in the ISM, plays an important role in the process of massive star formation. To better understand its impact at the pre and protostellar stages, high-angular resolution observations of polarized dust emission toward a large sample of massive dense cores are needed. To this end, we used the Atacama Large Millimeter Array in Band 6 (1.3 mm) in full polarization mode to map the polarized emission from dust grains at a physical scale of $\sim$2700 au in the massive protocluster W43-MM1. We used these data to measure the orientation of the magnetic field at the core scale. Then, we examined the relative orientations of the core-scale magnetic field, of the protostellar outflows determined from CO molecular line emission, and of the major axis of the dense cores determined from 2D Gaussian fit in the continuum emission. We found that the orientation of the dense cores is not random with respect to the magnetic field. Instead, the dense cores are compatible with being oriented 20-50${}^{°}$ with respect to the magnetic field. The outflows could be oriented 50-70${}^{°}$ with respect to the magnetic field, or randomly oriented with respect to the magnetic field, similar to current results in low-mass star-forming regions. In conclusion, the observed alignment of the position angle of the cores with respect to the magnetic field lines shows that the magnetic field is well coupled with the dense material; however, the 20-50${}^{°}$ preferential orientation contradicts the predictions of the magnetically-controlled core-collapse models. The potential correlation of the outflow directions with respect to the magnetic field suggests that, in some cases, the magnetic field is strong enough to control the angular momentum distribution from the core scale down to the inner part of the circumstellar disks where outflows are triggered.

Accepted by A&A, 8 pages, 4 figures

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• The JCMT BISTRO survey: alignment between outflows and magnetic fields in dense cores/clumps
• Collapse of turbulent massive cores with ambipolar diffusion and hybrid radiative transfer II. Outflows
• On the magnetic field properties of protostellar envelopes in Orion
• The Explosion in Orion-KL as Seen by Mosaicking the Magnetic Field with ALMA
• Alignment of dense molecular core morphology and velocity gradients with ambient magnetic fields
• Magnetic field alignment with dense cores in the transition between cloud and core scales