Unveiling AGN feedback via PAH emission at Cosmic Noon with JWST

Active galactic nuclei (AGN) at the centre of most massive galaxies are believed to regulate star formation in their host galaxies. This feedback manifests in the form of jet or radiation-pressure driven winds that can extend out to kpc scales. Feedback from AGN and/or star formation is expected to be greatest at Cosmic Noon (1 < z < 3), where the volume-averaged SFR and BH growth rate peaks in the universe. One of the ways to test its presence is by searching for connections between multi-phase outflows and star-forming properties of the host galaxy. Emission from polycyclic aromatic hydrocarbons (PAHs) are reliable tracers of star formation, as they are likely excited by UV light from massive stars. However, PAH emission can also be destroyed due to radiation from the AGN. In this study, we present JWST/MIRI-MRS observations of PAH emission in AGN host galaxies at z ∼ 2. In most targets, the PAH emission is weak or absent in the central regions, but stronger in off-nuclear regions, suggesting that the AGN may have destroyed PAH molecules in the centre. Only one target displays a strong detection both in the centre as well as in the galaxy outskirts, out to tens of kpc scales. This suggests that AGN may suppress star formation in the central regions, leaving the outer regions of the galaxy less affected. Our results show that PAH emission at Cosmic Noon can therefore give us a hint on the ongoing star formation in AGN, especially where other tracers, like Hα, can be strongly affected by dust obscuration.