Two massive star forming regions at early evolutionary stages

We report sensitive ATCA radio continuum observations toward IRAS 15596−5301 and 16272−4837, two luminous objects (L > 2 × 10L⊙) thought to represent massive star forming regions in early stages of evolution (due to previously undetected radio emission at the 1σ level of 2 mJy per beam). Also reported are 1.2 millimeter continuum and a series of molecular line observations made with the SEST telescope. The radio continuum observations toward IRAS 15596−5301 reveal the presence of three distinct compact sources, with angular sizes of 2.7 to 8.8 (FWHM), all located within a region of 30 in diameter. Assuming that these are regions of ionized gas, we find that they have diameters of 0.06-0.2 pc, electron densities of 8×10−2×10 cm, and that they are excited by early B type stars. The 1.2-mm observations show that the dust emission arises from a region of 42 × 25 (FWHM) with a total flux of 5.8 Jy, implying a mass of 1.4×10 M⊙. The line observations indicate that IRAS 15596−5301 is associated with a molecular cloud with a FWHM angular size of 37 (∼ 0.4 pc radius at the distance of 4.6 kpc), a molecular hydrogen density of ∼ 4 × 10 cm and a rotational temperature of ∼ 27 K. We suggest that the massive dense core associated