The dynamical properties of dense filaments in the infrared dark cloud G035.39−00.33★

Abstract

Infrared Dark Clouds (IRDCs) are unique laboratories to study the initial\nconditions of high-mass star and star cluster formation. We present\nhigh-sensitivity and high-angular resolution IRAM PdBI observations of N2H+\n(1-0) towards IRDC G035.39-00.33. It is found that G035.39-00.33 is a highly\ncomplex environment, consisting of several mildly supersonic filaments\n(sigma_NT/c_s ~1.5), separated in velocity by <1 km s^-1 . Where multiple\nspectral components are evident, moment analysis overestimates the non-thermal\ncontribution to the line-width by a factor ~2. Large-scale velocity gradients\nevident in previous single-dish maps may be explained by the presence of\nsubstructure now evident in the interferometric maps. Whilst global velocity\ngradients are small (<0.7 km s^-1 pc^-1), there is evidence for dynamic\nprocesses on local scales (~1.5-2.5 km s^-1 pc^-1 ). Systematic trends in\nvelocity gradient are observed towards several continuum peaks. This suggests\nthat the kinematics are influenced by dense (and in some cases, starless)\ncores. These trends are interpreted as either infalling material, with\naccretion rates ~(7 \\pm 4)x10^-5 M_sun yr^-1 , or expanding shells with\nmomentum ~24 \\pm 12 M_sun km s^-1 . These observations highlight the importance\nof high-sensitivity and high-spectral resolution data in disentangling the\ncomplex kinematic and physical structure of massive star forming regions.\n