Feedback in Emerging extragAlactic Star clusTers, FEAST: JWST spots PAH destruction in NGC 628 during the emerging phase of star formation

We investigate the emergence phase of young star clusters in the nearby spiral galaxy NGC 628. We use JWST NIRCam and MIRI observations to create spatially resolved maps of the Paα-1.87 μm and Brα-4.05 μm hydrogen recombination lines, as well as the 3.3 μm and 7.7 μm emission from polycyclic aromatic hydrocarbons (PAHs). We extract 953 compact HII regions and analyze the PAH emission and morphology at ~10 pc scales in the associated photo-dissociation regions (PDRs). While HII regions remain compact, radial profiles help us to define three PAH morphological classes: compact (~ 42%), extended (~ 34%) and open (~24%). The majority of compact and extended PAH morphologies are associated with very young star clusters (<5 Myr), while open PAH morphologies are mainly associated with star clusters older than 3 Myr. We observe a general decrease in the 3.3 μm and 7.7 μm PAH band emission as a function of cluster age, while their ratio remains constant with age out to 10 Myr and morphological class. The recovered PAH_3.3 μ m/PAH_7.7 μ m ratio is lower than values reported in the literature for reference models and analyses conducted at larger physical scales. The 3.3 μm and 7.7 μm bands are typically associated to neutral and ionised PAHs, respectively. While we expected neutral PAHs to be suppressed in proximity of the ionizing source, the constant PAH_3.3 μ m/PAH_7.7 μ m ratio would indicate that both families of molecules disrupt at similar rates in proximity of the HII regions.