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

¹ Departamento de Astronomía, Universidad de Chile, Camino El Observatorio 1515, Las Condes, 36D Casilla, Santiago, Chile
e-mail: lgomez@das.uchile.cl
² Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
e-mail: wyrowski@mpifr.de; kmenten@mpifr.de
³ CSIRO Astronomy and Space Science, PO Box 76, NSW 1710 Epping, Australia
⁴ European Southern Observatory, Alonso de Córdova 3107, Vitacura, 19001 Casilla, 19 Santiago, Chile
e-mail: fschulle@apex-telescope.org
⁵ Centro de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, Apdo. Postal 3–72, 58090 Morelia, Michoacán, México
e-mail: j.ballesteros@crya.unam.mx

Received: 18 July 2013
Accepted: 27 November 2013

Abstract

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.