Unveiling the main heating sources in the Cepheus A HW2 region

We present high angular resolution PdBI images (beam of ~0.33'') of the J=27-26 line from several vibrational levels (v7=1 and v6=1) of HC3N toward Cepheus A HW2. These images reveal the two main heating sources in the cluster: one centered in the disk collimating the HW2 radio jet (the HW2 disk), and the other associated with a hot core 0.3'' northeast HW2 (the HC). This is the first time that vibrationally excited emission of HC3N is spatially resolved in a disk. The kinematics of this emission shows that the HW2 disk rotates following a Keplerian law. We derive the temperature profiles in the two objects from the excitation of HC3N along the HW2 disk and the HC. These profiles reveal that both objects are centrally heated and show temperature gradients. The inner and hotter regions have temperatures of 350+-30K and 270+-20K for the HW2 disk and the HC, respectively. In the cooler and outer regions, the temperature drops to 250+-30K in the HW2 disk, and to 220+-15K in the HC. The estimated luminosity of the heating source of the HW2 disk is ~2.2E4Lo, and 3000Lo for the HC. The most massive protostar in the HW2 region is the powering source of the HW2 radio jet. We discuss the formation of multiple systems in this cluster. The proximity of the HC to HW2 suggest that these sources likely form a binary system of B stars, explaining the observed precession of the HW2 radio jet.