Magnetic fields in Massive Star-Forming Regions (MagMaR). VIII. Magnetic field overrun by gravity in GGD 27's accretion streamers

arXiv:2607.17160 · astro-ph.SR, astro-ph.GA · Submitted 2026-07-19 · Read on arXiv

M. Fernández-López, J. A. López-Vázquez, J. M. Girart, P. Sanhueza, L. A. Zapata, P. C. Cortés, H. Beuther, G. Busquet, I. W. Stephens, K. Morii, N. Añez-López, C. -F. Lee, Q. Zhang, M. T. Beltrán, S. Curiel, F. A. Olguin, E. J. Chung, P. Saha, S. Li, P. M. Koch, J. Hwang, C. -Y. Law, J. -H. Kang

Facultad de Ciencias Astronómicas y Geofísicas · Academia Sinica Institute of Astronomy and Astrophysics, Taiwan · Institut d'Estudis Espacials de Catalunya · Department of Astronomy, School of Science, The University of Tokyo, Japan · Instituto de Radioastronomía y Astrofísica · National Radio Astronomy Observatory, USA · Max Planck Institute for Astronomy, Germany · Institut d'Estudis Espacials de Catalunya · Department of Earth, Environment and Physics, Worcester State University, USA · Center for Astrophysics | Harvard \& Smithsonian, USA · Université Paris-Saclay, France · Academia Sinica Institute of Astronomy and Astrophysics, Taiwan · Center for Astrophysics | Harvard \& Smithsonian, USA · INAF-Osservatorio Astrofisico di Arcetri, Italy · Instituto de Astronomía · National Astronomical Observatory of Japan, Japan · Korea Astronomy and Space Science Institute, Republic of Korea · National Astronomical Observatory of Japan, Japan · Key Laboratory of Modern Astronomy and Astrophysics · Academia Sinica Institute of Astronomy and Astrophysics, Taiwan · Department of Earth and Planetary Sciences, Kyushu University, Japan · INAF-Osservatorio Astrofisico di Arcetri, Italy · Korea Astronomy and Space Science Institute, Republic of Korea

astro-ph.SR, astro-ph.GA

Submitted: 2026-07-19

Comments: 13 pages, 6 figures, 3 tables. Accepted by A&A

License: http://creativecommons.org/licenses/by-nc-sa/4.0/

The gist: Context.

Terminology

Abstract

Context. Accretion streamers connected to protostellar disks and/or envelopes are thought to transport material across several thousand of au. Whether the motions of the gas comprising these streamers are dominated by gravity, large scale external turbulence or the action of magnetic fields is still under scrutiny. Aims. The aim of this work is to understand the role of the magnetic fields in the star-formation processes, in particular the role that magnetic forces have in potentially leading flows of gas and the accretion onto the envelopes and disks orbiting protostars. Methods. First, we try to identify the large-scale accretion streamers toward the high-mass Young Stellar Object GGD 27-MM1 and fit their trajectories using the so-called Mendoza's model, a modification of the classical model of pure gravitational infalling motion of fluid particles in a potential well. Second, we estimate the strength of the magnetic field associated with the streamers. Then, we determine if the streamers are dominated by magnetic or centrifugal forces. Results. Inspecting the Atacama Large Millimeter/submillimeter Array (ALMA) H 2 CO cube we were able to identify four accretion streamers spreading up to about 7,000 au and fit their trajectories in the position-position-velocity space. The polarized continuum emission reveals a good alignment of the magnetic field and the trajectory of the streamers. Using the Davis-Chandrasekhar-Fermi method, we derive estimates for the magnetic field strength, find that the streamers are sub-alfv'enic, and discuss (after estimating energy terms for turbulence, ordered motions, magnetic forces and gravity) a possible qualitative scenario in which, the gravitational well of the GGD 27-MM1 protostar dominates streamer gas motions over turbulence and magnetic forces at distances of about 3,000 au.

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