The initial conditions of high-mass star formation: radiative transfer models of IRDCs seen in the Herschel Hi-GAL survey^⋆

¹ School of Physics and Astronomy, Cardiff University, Queen’s Building, Cardiff CF24 3AA, UK
e-mail: lucy.wilcock@astro.cf.ac.uk
² Center for Astrophysics & Space Astronomy, University of Colorado, Boulder, CO, 80309, USA
³ School of Physics, University of Exeter, Stocker Road, Exeter, EX4 4QL, UK
⁴ Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
⁵ Instituto di Fisica dello Spazio Interplanetario, CNR, via Fosso del Cavaliere, 00133 Roma, Italy
⁶ Canadian Institute for Theoretical Astrophysics, University of Toronto, Toronto, Canada, M5S 3H8
⁷ Laboratoire AIM, CEA/DSM-CNRS-Université Paris Diderot, IFRU/Service d’Astrophysique, C.E. Saclay, Orme des merisiers, 91191 Gif-sur-Yvette, France
⁸ University of Calgary, Dept Physics-Astronomy, Calgary, AB T2N 1N4, Canada
⁹ Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA, 02138, USA
¹⁰ Centre for Astrophysics Research, Science and Technology Research Institute, University of Hertfordshire, AL10 9AB, UK

Received: 28 July 2010
Accepted: 7 December 2010

Abstract

The densest infrared dark clouds (IRDCs) may represent the earliest observable stage of high-mass star formation. These clouds are very cold, hence they emit mainly at far-infrared and sub-mm wavelengths. For the first time, Herschel has provided multi-wavelength, spatially resolved observations of cores within IRDCs, which, when combined with radiative transfer modelling, can constrain their properties, such as mass, density profile and dust temperature. We use a 3D, multi-wavelength Monte Carlo radiative transfer code to model in detail the emission from six cores in three typical IRDCs seen in the Hi-GAL survey (G030.50+00.95, G031.03+00.26 and G031.03+00.76), and thereby to determine the properties of these cores and compare them with their low-mass equivalents. We found masses ranging from 90 to 290 M_⊙ with temperatures from 8 to 11 K at the centre of each core and 18 to 28 K at the surface. The maximum luminosity of an embedded star within each core was calculated, and we rule out the possibility of significant high mass star formation having yet occurred in three of our cores.