2025RNAAS...9..205M

The IM Lup protoplanetary disk shows tentative evidence of an external photoevaporative wind based on its unusually extended and diffuse ¹²CO gas. Only shallow [C I] 1-0 observations exist toward IM Lup, which show a more compact radial distribution than that of ¹²CO, despite the expectation that atomic carbon should trace the outer interface of UV-irradiated ¹²CO. In this research note, we present a novel use of matched filtering to constrain the maximum extent of the underlying C I gas in IM Lup. We find evidence for C I emission at large radii (r ≈ 700-950 au) beyond what was previously detected in the image plane (r ≈ 600 au). Further deep and spatially resolved imaging of C I in IM Lup and other systems will be essential for disentangling the disk- versus wind-driven components of C I to better understand how line emission traces photoevaporative processes.