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

Abstract

Aims. It has been proposed that the magnetic field, which is pervasive in the interstellar medium, plays an important role in the process of massive star formation. To better understand the impact of the magnetic field at the pre- and protostellar stages, high-angular resolution observations of polarized dust emission toward a large sample of massive dense cores are needed. We aim to reveal any correlation between the magnetic field orientation and the orientation of the cores and outflows in a sample of protostellar dense cores in the W43-MM1 high-mass star-forming region. Methods. 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 ~2700 au. 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, and of the major axis of the dense cores determined from a 2D Gaussian fit in the continuum emission. Results. We find 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. As for the outflows, they could be oriented 50–70° with respect to the magnetic field, or randomly oriented with respect to the magnetic field, which is similar to current results in low-mass star-forming regions. Conclusions. 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.

The JCMT BISTRO Survey: Alignment between Outflows and Magnetic Fields in Dense Cores/Clumps

“…Nevertheless, our results do not rule out the possibility of random orientations of the outflows and the magnetic fields. A similar trend that outflows may have preferred orientations with respect to the magnetic fields has also been suggested in the high-mass star-forming region W43-MM1 (Arce et al 2020), although the possibility of random orientations of outflows and magnetic fields is also not ruled out in that study.…”

Collapse of turbulent massive cores with ambipolar diffusion and hybrid radiative transfer

“…Interestingly, Galametz et al (2018) show that the best alignment between the magnetic fields and the outflow axis is observed for sources with no large (>100 AU) disk or multiplicity. Finally, in the highmass regime, Arce-Tord et al (2020) reach the same conclusions as Hull et al (2014): their distribution is best fitted by either a 50−70 deg preferential orientation or a random orientation between the outflow and the magnetic fields.…”

Collapse of turbulent massive cores with ambipolar diffusion and hybrid radiative transfer II. Outflows

“…Interestingly, Galametz et al (2018) show that the best alignment between the magnetic fields and the outflow axis is observed for sources with no large (> 100 AU) disk nor multiplicity. Finally, in the highmass regime, Arce-Tord et al (2020) reach the same conclusions as Hull et al (2014): their distribution is best fitted by either a 50 − 70 deg preferential orientation or a random orientation between the outflow and the magnetic fields.…”