Kinematic structure of massive star-forming regions

I. Accretion along filaments^⋆

¹ Max-Planck-Institut für Astronomie (MPIA), Königstuhl 17, 69117 Heidelberg, Germany
e-mail: last-name@mpia.de
² Graduate School of Informatics and Engineering, The University of Electro-Communications, Chofu, 182-8585, Tokyo, Japan
³ AIM Paris-Saclay, CEA/DSM/IRFU – CNRS/INSU – Université Paris Diderot, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France
⁴ Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany

Received: 22 March 2013
Accepted: 7 January 2014

Abstract

Context. The mid- and far-infrared view on high-mass star formation, in particular with the results from the Herschel space observatory, has shed light on many aspects of massive star formation. However, these continuum studies lack kinematic information.

Aims. We study the kinematics of the molecular gas in high-mass star-forming regions.

Methods. We complemented the PACS and SPIRE far-infrared data of 16 high-mass star-forming regions from the Herschel key project EPoS with N₂H⁺ molecular line data from the MOPRA and Nobeyama 45 m telescope. Using the full N₂H⁺ hyperfine structure, we produced column density, velocity, and linewidth maps. These were correlated with PACS 70 μm images and PACS point sources. In addition, we searched for velocity gradients.

Results. For several regions, the data suggest that the linewidth on the scale of clumps is dominated by outflows or unresolved velocity gradients. IRDC 18454 and G11.11 show two velocity components along several lines of sight. We find that all regions with a diameter larger than 1 pc show either velocity gradients or fragment into independent structures with distinct velocities. The velocity profiles of three regions with a smooth gradient are consistent with gas flows along the filament, suggesting accretion flows onto the densest regions.

Conclusions. We show that the kinematics of several regions have a significant and complex velocity structure. For three filaments, we suggest that gas flows toward the more massive clumps are present.