The mass distribution of clumps within infrared dark clouds. A Large APEX Bolometer Camera study

Aims: We present an analysis of the dust continuum emission at 870 μm in order to investigate the mass distribution of clumps within infrared dark clouds (IRDCs).
Methods: We map six IRDCs with the Large APEX BOlometer CAmera (LABOCA) at APEX, reaching an rms noise level of σ_rms = 28-44 mJy beam^-1. The dust continuum emission coming from these IRDCs was decomposed by using two automated algorithms, Gaussclumps and Clumpfind. Moreover, we carried out single-pointing observations of the N₂H⁺ (3-2) line toward selected positions to obtain kinematic information.
Results: The mapped IRDCs are located in the range of kinematic distances of 2.7-3.2 kpc. We identify 510 and 352 sources with Gaussclumps and Clumpfind, respectively, and estimate masses and other physical properties assuming a uniform dust temperature. The mass ranges are 6-2692 M_⊙ (Gaussclumps) and 7-4254 M_⊙ (Clumpfind), and the ranges in effective radius are ~0.10-0.74 pc (Gaussclumps) and 0.16-0.99 pc (Clumpfind). The mass distribution, independent of the decomposition method used, is fitted by a power law, dN/dM ∝ M^α, with an index (α) of -1.60 ± 0.06, consistent with the CO mass distribution and other high-mass star-forming regions.

Based on data acquired with the Atacama Pathfinder Experiment (APEX). APEX is a collaboration between the Max-Planck-Institut für Radioastronomie, the European Southern Observatory, and the Onsala Space Observatory.Full Tables 3 and 4 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/561/A148