The recently upgraded radio telescopes provide high quality data that enable unprecedented studies over star forming regions. For instance, deep observations over nearby star forming regions unveil the presence of an extremely rich radio source population, suggesting that most of the radio sources in star forming regions are hidden below the detection threshold. Based on this, we carried out high angular resolution (0.2 arcsec aprox.). VLA observations of selected star forming regions focusing, in some cases, in UCHII regions.
The observations, taken in several epochs, had as a preliminar goal to report additional cases of compact radio sources embedded in star forming regions.
Indeed, our results suggest that the presence these radio sources close to massive young stars is a common phenomena, possibly inherent to all star forming regions.
Although we cannot establish yet an unambiguous nature for the newly detected radio sources, we assess some of their observational properties. According to the results, we can distinguish between two classes of compact sources. One class corresponds to sources that probably are deeply embedded in the dense ionized gas of UCHII regions. These sources are being photo-evaporated by the exciting star of the region. They may play a crucial role in the evolution of the UCHII region as the photo-evaporated material could replenish for 10^4-10^5 yr the expanding plasma and might provide a solution to the so-called ‘lifetime’ problem for these regions. The other class of compact sources is not associated with the densest ionized gas of the region. Most of these sources appear unresolved and their properties are varied, possibly being more evolved objects. We speculate on the similarity between these sources and those of the Orion population of radio sources.