Denise R. Gonçalves
CO – ALMA constraints for the coldest material in low-ionization jets of PNe
Our knowledge of planetary nebulae (PNe) is primarily based on their large-scale ionized components. However, PNe also host low-ionization structures (LISs), frequently appearing as small-scale, highly collimated pairs. Although the presence, origin, and implications of these structures remain unclear, their origin seems to be closely connected with the launching and propagation of the jetlike outflows (Rechy-García et al. 2022) that shape the transition from the asymptotic giant branch to the PN phase. A particularly puzzling aspect is that, despite being prominent in low-ionization lines ([NII], [OII], [SII]) –and contrary to theoretical predictions (e.g., Balick et al. 2020, as a recent example)– the measured electron density of LISs is lower than in the surrounding large-scale nebular components (Gonçalves et al. 2009; Mari et al. 2023). This fact suggests that a significant amount of neutral and molecular gas may be hidden within LIS pairs. Our group’s observational campaign to uncover this hidden component through near-IR H2 emission has yielded positive results in every PNe studied so far (Akras et al. 2017, 2020; Mari et al. 2025, in prep.).
Currently, we directed our observational efforts toward the detection of CO –the second most abundant molecule– using millimeter single-dishes and interferometers. In this contribution, the focus are prominent LISs where molecular H, as well as atomic C and O have already been observed. Here we present preliminary results from our single-dish and ALMA observations, alongside photo-dissociation models that allow robust interpretation of the data (Gonçalves et al. 2025, in prep.).
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CO – ALMA constraints for the coldest material in low-ionization jets of PNe
