Star Formation at the Periphery of a Molecular Superbubble: The Case of G12.79+0.43

We present a multiwavelength investigation of the molecular cloud complex G12.79+0.43, which extends over about18' on the sky. Several infrared- and radio-bright regions are arranged along an irregular rim, surrounding a central region characterised by diffuse 24 mu m emission. CO molecular line observations reveal three prominent velocity components along the line of sight. Low-frequency radio continuum observations at 666 and 1300 MHz show diffuse emission spanning about10.5' (about 7.3 pc), predominantly filling the central region enclosed by the infrared-bright structures. We identify 70 compact radio sources and six regions across the cloud complex, which are likely powered by early B-type ZAMS stars. Using infrared data, we identify a total of 82 YSO candidates, including 28 Class I sources, distributed across the cloud complex. On larger scales, the kinematics of the molecular gas over a 2 times2 field indicate that G12.79+0.43 is located along the rim of a larger molecular superbubble (diameter about50 pc) that also encompasses the well-known W33 region. The inferred expansion age of this superbubble is about0.3 Myr. While the spatial association between G12.79+0.43 and the superbubble is evident, the current data do not allow us to establish a clear causal connection between the superbubble evolution and the ongoing star formation within G12.79+0.43.