The spine of the swan: a Herschel study of the DR21 ridge and filaments in Cygnus X^⋆,⋆⋆

¹ AIM Paris-Saclay, CEA/DSM/IRFU – CNRS/INSU – Université Paris Diderot, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France
e-mail: martin.hennemann@cea.fr
² Université de Bordeaux, LAB, UMR5804, 33270 Floirac, France
³ CNRS, LAB, UMR5804, 33270 Floirac, France
⁴ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
⁵ Herschel Science Centre, ESAC, ESA, PO Box 78, Villanueva de la Cañada, 28691 Madrid, Spain
⁶ Canadian Institute for Theoretical Astrophysics – CITA, University of Toronto, 60 St. George Street, Toronto, Ontario, M5S 3H8, Canada
⁷ Laboratoire d’Astrophysique de Marseille, CNRS/INSU – Université de Provence, 13388 Marseille Cedex 13, France
⁸ Department of Physics, West Virginia University, Morgantown, WV 26506, USA
⁹ IRAP, CNRS (UMR 5277), Université Paul Sabatier, 9 avenue du Colonel Roche, 31028 Toulouse Cedex 4, France
¹⁰ National Research Council of Canada, Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria, BC V9E 2E7, Canada
¹¹ Istituto di Astrofisica e Planetologia Spaziali – IAPS, Istituto Nazionale di Astrofisica – INAF, via Fosso del Cavaliere 100, 00133 Roma, Italy
¹² National Astronomical Observatories, Chinese Academy of Sciences, A20 Datun Road, Chaoyang District, 100012 Beijing, PR China
¹³ Institut d’Astrophysique de Paris, Université Pierre et Marie Curie (UPMC), CNRS UMR 7095, 75014 Paris, France
¹⁴ Jeremiah Horrocks Institute, University of Central Lancashire, Preston PR1 2HE, UK
¹⁵ Department of Physics & Astronomy, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK
¹⁶ Space Science & Technology Department, CCLRC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX, UK

Received: 17 April 2012
Accepted: 5 June 2012

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 higher than 10²³ cm^-2 over a region of 2.3 pc². It shows substructured column density profiles and branches into two major filaments in the north. The masses in the filaments range between 130 and 1400 M_⊙, whereas the mass in the ridge is 15 000 M_⊙. 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 coresformed 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.