The spine of the swan: A Herschel study of the DR21 ridge and filaments in Cygnus X

TL;DR

This Herschel study reveals the detailed structure and dynamics of the DR21 ridge and filaments in Cygnus X, highlighting their role in high-mass star formation through filament accretion, core formation, and merging processes.

Contribution

It provides high-resolution maps of the DR21 environment, characterizing filamentary structures, mass distribution, and star formation activity, offering new insights into high-mass star formation mechanisms.

Findings

The DR21 ridge has a mass of 15,000 Msun and high column densities.

Filaments are gravitationally unstable and form cores and protostars.

Filament accretion and core collisions likely drive high-mass star formation.

Abstract

In order to characterise the cloud structures responsible for the formation of high-mass stars, we present Herschel observations of the DR21 environment. Maps of the column density and dust temperature unveil the structure of the DR21 ridge and several connected filaments. The ridge has column densities larger than 1e23/cm^2 over a region of 2.3 pc^2. It shows substructured column density profiles and branching into two major filaments in the north. The masses in the studied filaments range between 130 and 1400 Msun whereas the mass in the ridge is 15000 Msun. The accretion of these filaments onto the DR21 ridge, suggested by a previous molecular line study, could provide a continuous mass inflow to the ridge. In contrast to the striations seen in e.g., the Taurus region, these filaments are gravitationally unstable and form cores and protostars. These cores formed in the filaments potentially fall into the ridge. Both inflow and collisions of cores could be important to drive the observed high-mass star formation. The evolutionary gradient of star formation running from DR21 in the south to the northern branching is traced by decreasing dust temperature. This evolution and the ridge structure can be explained by two main filamentary components of the ridge that merged first in the south.