Speaker
Description
Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous carbonaceous molecules in the interstellar medium, tracing the interaction between ultraviolet radiation fields and molecular material. In protoplanetary disks, they are widely used as diagnostics of disk surface chemistry, UV processing, and ionization structure. Using recently obtained JWST/NIRSpec and MIRI IFU observations of the edge-on disks ESO-H$\alpha$ 574, HV Tau C, OphE MM3, Oph 163131, Flying Saucer, and LkH$\alpha$ 263C, we analyze near- and mid-infrared emission features commonly attributed to PAHs. We first assess the spatial origin of the emission to distinguish disk-associated PAH features from background cloud contamination, exploiting the edge-on geometries and spatially resolved IFU data. For sources where the emission is demonstrably disk-confined, we derive physically motivated band ratios (i.e., 3.3/11.3 $\mu m$, 11.3/7.7 $\mu m$, and 3.4/3.3 $\mu m$) to constrain PAH representative sizes as well as ionization and aliphatic fractions. Where signal-to-noise permits, we construct spatially resolved ratios to trace vertical and radial variations in PAH properties across the disks. Preliminary results indicate predominantly small- to medium-sized PAHs ($N_c \approx 30–100$), with regionally dependent ionization states that are either strongly neutral or strongly ionized. Several systems exhibit systematic vertical gradients consistent with irradiation-driven processing in disk surface layers, while mid-plane regions show suppressed aromatic emission, likely due to shielding and grain growth. These findings demonstrate that PAH emission in edge-on disks provides a spatially resolved diagnostic of disk irradiation and the chemical state of PAHs, including ionization and molecular structure. When combined with JWST constraints on gas excitation and ice composition, PAHs emerge as a powerful probe of radiation-driven evolution, ionization balance, and the processing of aromatic carbon during planet formation.
| Participate the oral/poster presentation award competition | No |
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