The Effect of AGN Feedback on the Lyman- Forest Signature of Galaxy Protoclusters at z~2. 3

The intergalactic medium (IGM) in the vicinity of galaxy protoclusters are interesting testbeds to study complex baryonic effects such as gravitational shocks and feedback. Here, we utilize hydrodynamical simulations from the SIMBA and The Three Hundred suites to study the mechanisms influencing large-scale Lyman- transmission in 2<z<2. 5 protoclusters observed in the COSMOS field. We focus on the matter overdensity-Lyman- transmission relation (ₘ-F) on Megaparsec-scales in these protoclusters, which is hypothesized to be sensitive to the feedback implementations. The lower-density regions represented by the SIMBA-100 cosmological volume trace the power-law ₘ-F relationship often known as the fluctuating Gunn-Peterson approximation (FGPA). This trend is continued into higher-density regions covered by the 300-GadgetMUSIC simulations that implement stellar feedback only. The 300-GadgetX and 300-SIMBA simulations, with AGN thermal and AGN jet feedback respectively, exhibit progressively more Lyman- transmission at fixed overdensity. Compared with the 7 protoclusters observed in the CLAMATOCOSTCO data, only 2 appear consistent with the FGPA. The others exhibit clear deviations: 4 follow the trend of AGN X-ray thermal feedback models while the COSTCO-I protocluster appears to reflect intense jet feedback. The large discrepancy with the stellar-feedback-only 300-GadgetMUSIC model disfavours large-scale heating from gravitational collapse and/or stellar feedback. This indicates that some form of AGN feedback is likely at play in the observed protoclusters, and possibly long-ranged AGN jets in the case of COSTCO-I. While more detailed and resolved simulations are required to move forward, our findings open new avenues for probing AGN feedback at Cosmic Noon.