Speaker
Description
The Orion Nebula Cluster hosts more than 200 protoplanetary disks (proplyds) identified at optical, infrared and radio wavelengths, exposed to the intense ultraviolet radiation from nearby massive stars. These objects provide a unique laboratory to investigate externally photoevaporated disks and the impact of massive stars on planet-forming environments. Recent ALMA observations have enabled the first detection of millimeter hydrogen radio recombination lines (RRLs) toward 16 proplyds, opening a new diagnostic window to constrain the physical conditions and kinematics of their ionized gas. In this work, we expand the characterization of ionized gas in proplyds by combining centimeter radio continuum observations with radio recombination line measurements obtained from VLA C-band data from the VLA Orion A Large Survey (VOLS) project. The continuum emission traces free-free radiation from the ionized photoevaporative envelopes, allowing us to measure flux densities and spectral index of the emission. In this work, we focus on the analysis of the RRLs which provides constraints on the electron temperature, density, and gas dynamics within the ionized flows. By comparing RRLs observed at different wavelengths we also evaluate the role of non-LTE effects and pressure broadening in shaping the line profiles. These observations provide new constraints on the structure and physical conditions of ionized proplyd envelopes, improving our understanding of disk photoevaporation, massloss rates, and the evolution of protoplanetary disks in massive star-forming regions.
