Spatially resolved PAH3.3 emission and stellar ages in ram pressure stripped clumps at z ∼ 0.3
February 2026 • 2026A&A...706A.300B
Abstract • Ram pressure stripping (RPS) plays a crucial role in shaping galaxy evolution in dense environments, yet its impact on the molecular and dusty phases of the interstellar medium remains poorly understood. We present JWST/NIRCam 3.3 μm polycyclic aromatic hydrocarbon (PAH) emission maps for the nine most striking RPS galaxies in the Abell 2744 cluster at redshift zcl = 0.306, tracing the effects of environmental processes on small dust grains. Exploiting multi-band JWST/NIRCam and HST photometry, we performed a spatially resolved ultraviolet (UV) to mid-infrared (MIR) spectral energy distribution (SED) fitting to characterise stellar populations in both galactic disks and clumps detected in the stripped tails. We detected PAH3.3 emission in eight of the nine galaxies at 5σ, with morphologies revealing disk truncation and elongation along the RPS direction. In three galaxies, PAH3.3 emission is also found in star-forming clumps embedded in the stripped tails up to a distance of 40 kpc. Star formation rates inferred from PAH3.3 emission are in agreement with those derived from SED fitting averaged over the past 100 Myr within an intrinsic scatter of 0.4 dex, but the relation appears to be age-dependent. The spatial correlation between the PAH strength, stellar age, and star formation rate (SFR) is consistent across disks and tails and demonstrates that PAH-carrying molecules can survive and become stripped by ram pressure. Finally, age gradients revealed by the SED fitting provide observational evidence of the fireball model in star-forming, stripped clumps of galaxies at z ∼ 0.3. This work represents the first detailed study of PAH emission in cluster galaxies, offering new insights into the fate of dust and star formation in extreme environments.
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