The Cygnus Allscale Survey of Chemistry and Dynamical Environments: CASCADE

II. A detailed kinematic analysis of the DR21 Main outflow

¹ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
e-mail: iskretas@mpifr-bonn.mpg.de
² Argelander-Institut für Astronomie, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
³ Institute of Astronomy, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, ul. Grudziądzka 5, 87-100 Toruń, Poland
⁴ Max Planck Insitute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
⁵ Department of Astronomy, University of Florida, PO Box 112055, Gainesville, FL 32611-2055, USA
⁶ Tecnologico de Monterrey, Escuela de Ingenieria y Ciencias, Avenida Eugenio Garza Sada 2501, Monterrey 64849, Mexico
⁷ Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany
⁸ I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany
⁹ IRAM, 300 rue de la Piscine, Domaine Universitaire de Grenoble, 38406 St.-Martin-d’Hères, France
¹⁰ Department of Astrophysics, University of Vienna, Turkenschanzstrasse 17, 1180 Vienna, Austria

Received: 5 May 2023
Accepted: 17 September 2023

Abstract

Context. Molecular outflows are believed to be a key ingredient in the process of star formation. The molecular outflow associated with DR21 Main in Cygnus-X is one of the most extreme molecular outflows in the Milky Way in terms of mass and size. The outflow is suggested to belong to a rare class of explosive outflows formed by the disintegration of protostellar systems.

Aims. We aim to explore the morphology, kinematics, and energetics of the DR21 Main outflow, and to compare those properties to confirmed explosive outflows in order to unravel the underlying driving mechanism behind DR21.

Methods. We studied line and continuum emission at a wavelength of 3.6 mm with IRAM 30 m and NOEMA telescopes as part of the Cygnus Allscale Survey of Chemistry and Dynamical Environments (CASCADE) program. The spectra include (J = 1−0) transitions of HCO⁺, HCN, HNC, N₂H⁺, H₂CO, and CCH, which trace different temperature and density regimes of the outflowing gas at high velocity resolution (~0.8 km s⁻¹). The map encompasses the entire DR21 Main outflow and covers all spatial scales down to a resolution of 3″ (~0.02 pc).

Results. Integrated intensity maps of the HCO⁺ emission reveal a strongly collimated bipolar outflow with significant overlap of the blueshifted and redshifted emission. The opening angles of both outflow lobes decrease with velocity, from ~80 to 20° for the velocity range from 5 to 45 km s⁻¹ relative to the source velocity. No evidence is found for the presence of elongated, “filament-like” structures expected in explosive outflows. N₂H⁺ emission near the western outflow lobe reveals the presence of a dense molecular structure, which appears to be interacting with the DR21 Main outflow.

Conclusions. The overall morphology as well as the detailed kinematics of the DR21 Main outflow are more consistent with a typical bipolar outflow than with an explosive counterpart.