Disk fragmentation in high-mass star formation

High-resolution observations towards AFGL 2591-VLA 3^★

¹ Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
e-mail: suemeyye.suri@univie.ac.at
² Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands
³ I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937, Köln, Germany
⁴ IRAM, 300 rue de la Piscine, Domaine Universitaire, 38406 St.-Martin-d’Hères, France
⁵ INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
⁶ Laboratoire d’astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, allée Geoffroy Saint-Hilaire, 33615 Pessac, France
⁷ Academia Sinica Institute of Astronomy and Astrophysics, No.1, Sec. 4, Roosevelt Rd, Taipei 10617, Taiwan, ROC
⁸ CAS Key Laboratory of FAST, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, PR China
⁹ National Astronomical Observatory of Japan, National Institutes of Natural Sciences, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
¹⁰ School of Physics & Astronomy, University of Leeds, Leeds LS2 9JT, UK
¹¹ UK Astronomy Technology Centre, Royal Observatory Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, UK
¹² Zentrum für Astronomie der Universität Heidelberg, Institut für Theoretische Astrophysik, Albert-Ueberle-Straße 2, 69120 Heidelberg, Germany
¹³ Institut für Astronomie und Astrophysik, Universität Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
¹⁴ INAF, Osservatorio Astronomico di Cagliari, Via della Scienza 5, 09047, Selargius (CA), Italy
¹⁵ Astrophysics Research Institute, Liverpool John Moores University, Liverpool, L3 5RF, UK
¹⁶ European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
¹⁷ Instituto de Radioastronomía y Astrofísica (IRyA), UNAM, Apdo. Postal 72-3 (Xangari), Morelia, Michoacán 58089, Mexico
¹⁸ Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85748 Garching, Germany
¹⁹ Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S4M1, Canada
²⁰ School of Physics & Astronomy, Cardiff University, Queen’s building, The parade, Cardiff, CF24 3AA, UK
²¹ Department of Chemistry, Ludwig Maximilian University of Munich, Butenandtstr. 5-13, House F, 81377 Munich, Germany
²² Centre for Astrophysics and Planetary Science, University of Kent, Canterbury, CT2,7NH, UK
²³ Max-Planck-Institut für Radioastronomie (MPIfR), Auf dem Hügel 69, 53121 Bonn, Germany
²⁴ Universidad Autonoma de Chile, Avda Pedro de Valdivia 425, Providencia, Santiago de Chile, Chile

Received: 31 March 2021
Accepted: 14 August 2021

Abstract

Context. Increasing evidence suggests that, similar to their low-mass counterparts, high-mass stars form through a disk-mediated accretion process. At the same time, formation of high-mass stars still necessitates high accretion rates, and hence, high gas densities, which in turn can cause disks to become unstable against gravitational fragmentation.

Aims. We study the kinematics and fragmentation of the disk around the high-mass star forming region AFGL 2591-VLA 3 which was hypothesized to be fragmenting based on the observations that show multiple outflow directions.

Methods. We use a new set of high-resolution (0′′.19) IRAM/NOEMA observations at 843 μm towards VLA 3 which allow us to resolve its disk, characterize the fragmentation, and study its kinematics. In addition to the 843 μm continuum emission, our spectral setup targets warm dense gas and outflow tracers such as HCN, HC₃N and SO₂, as well as vibrationally excited HCN lines.

Results. The high resolution continuum and line emission maps reveal multiple fragments with subsolar masses within the inner ~1000 AU of VLA 3. Furthermore, the velocity field of the inner disk observed at 843 μm shows a similar behavior to that of the larger scale velocity field studied in the CORE project at 1.37 mm.

Conclusions. We present the first observational evidence for disk fragmentation towards AFGL 2591-VLA 3, a source that was thought to be a single high-mass core. While the fragments themselves are low-mass, the rotation of the disk is dominated by the protostar with a mass of 10.3 ± 1.8 M_⊙. These data also show that NOEMA Band 4 can obtain the highest currently achievable spatial resolution at (sub-)mm wavelengths in observations of strong northern sources.