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