Kinematic structure of massive star-forming regions - I. Accretion along filaments

TL;DR

This study investigates the kinematic properties of molecular gas in high-mass star-forming regions, revealing complex velocity structures and evidence of gas flows along filaments that may contribute to star formation.

Contribution

It provides detailed kinematic maps using N2H+ line data, demonstrating gas flows and velocity gradients in high-mass star-forming regions, which were previously lacking in continuum studies.

Findings

Velocity gradients suggest gas flows along filaments toward dense regions.

Regions larger than 1pc show velocity gradients or fragmentation into distinct velocity structures.

Evidence of accretion flows onto dense clumps in several filaments.

Abstract

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. We study the kinematics of the molecular gas in high-mass star-forming regions. 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 45m telescope. Using the full N2H+ hyperfine structure, we produced column density, velocity, and linewidth maps. These were correlated with PACS 70micron images and PACS point sources. In addition, we searched for velocity gradients. For several regions, the data suggest that the linewidth on the scale of clumps is dominated by outflows or unresolved velocity gradients. IRDC18454 and G11.11 show two velocity components along several lines of sight. We find that all regions with a diameter larger than 1pc 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. 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.