Interferometric multi-wavelength (sub)millimeter continuum study of the young high-mass protocluster IRAS 05358+3543^*

¹ Max-Planck-Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany e-mail: beuther@mpia.de
² Max-Planck-Institute for Radioastronomy, Auf dem Hügel 69, 53121 Bonn, Germany e-mail: name@mpifr-bonn.mpg.de
³ European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany e-mail: sleurini@eso.org
⁴ Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA e-mail: qzhang@cfa.harvard.edu

Received: 14 November 2006
Accepted: 9 February 2007

Abstract

Aims.We study the small-scale structure of massive star-forming regions through interferometric observations in several (sub)mm wavelength bands. These observations resolve multiple sources, yield mass and column density estimates, and give information about the density profiles as well as the dust and temperature properties.

Methods.We observed the young massive star-forming region IRAS 05358+3543 at high spatial resolution in the continuum emission at 3.1 and 1.2 mm with the Plateau de Bure Interferometer, and at 875 and 438 μm with the Submillimeter Array. The observations are accompanied by VLA 3.6 cm archival continuum data.

Results.We resolve at least four continuum sub-sources that are likely of protostellar nature. Two of them are potentially part of a proto-binary system with a projected separation of 1700 AU. Additional (sub)mm continuum peaks are not necessarily harboring protostars but maybe caused by the multiple molecular outflows. The spectral energy distributions (SEDs) of the sub-sources show several features. The main power house mm1, which is associated with CH₃OH maser emission, a hypercompact Hii region and a mid-infrared source, exhibits a typical SED with a free-free emission component at cm and long mm wavelengths and a cold dust component in the (sub)mm part of the spectrum (spectral index between 1.2 mm and 438 μm ). The free-free emission corresponds to a Lyman continuum flux of an embedded 13  B1 star. The coldest source of the region, mm3, has between 1.2 mm and 875 μm, but has lower than expected fluxes in the shorter wavelength 438 μm band. This turnover of the Planck-function sets an upper limit on the dust temperature of mm3 of approximately 20 K. The uv-data analysis of the density structure of individual sub-cores reveals distributions with power-law indices between 1.5 and 2. This resembles the density distributions of the larger-scale cluster-forming clump as well as those from typical low-mass cores.