Kaleidoscope of irradiated disks: MUSE observations of proplyds in the Orion Nebula Cluster

The first protoplanetary disks were detected in the Orion Nebula Cluster (ONC) with the Hubble Space Telescope (HST) in 1990s. These disks appeared with teardrop-shaped clouds of ionized gas surrounding them, clearly visible in optical forbidden emission lines. This characteristic shape is caused by massive OB stars, which emit ultraviolet radiation and irradiate the disks. Due to the proximity of the ONC, such objects—called proplyds—provide a unique opportunity to study external photoevaporation in the act. We present unprecedented data of 12 proplyds in the ONC acquired with MUSE-NFM. This data reveals the size of the ionization front as a function of the ionizing field in a multitude of optical forbidden emission lines, most of which were never studied with HST. Analyzing these first spatially and spectrally resolved images of proplyds, combined with available ALMA data, allow us to provide constraints on the mass loss rate of these objects. Furthermore, we detect the forbidden carbon emission in proplyds for the first time, which we show to trace the surface of the disk and the base of externally photoevaporated wind. MUSE enables the characterization of proplyds in striking detail, and opens the scene to study more distant and massive star-forming regions—the locations that best represent the natal environments of known exoplanets.