Context :

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 \mu m 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 CH _ { 3 } OH maser emission , a hypercompact H ii 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 \mu m \alpha \sim 3.6 ) .
The free-free emission corresponds to a Lyman continuum flux of an embedded 13 M _ { \odot } B1 star .
The coldest source of the region , mm3 , has \alpha \sim 3.7 between 1.2 mm and 875 \mu m , but has lower than expected fluxes in the shorter wavelength 438 \mu m 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 . The files for figures 2 , 3 , 4 & 6 are also available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr ( 130.79.128.5 ) or via http : //cdsweb.u-strasbg.fr/cgi-bin/qcat ? J/A+A/ .

Conclusions :