Speaker
Description
Galaxy protoclusters (PCs) at $z\gtrsim2$ are dense regions extending up to few Mpc in which massive cold gas and elevated rates of galaxy interactions trigger intense, often dust-obscured, star formation in the member galaxies. These mechanisms are also expected to promote super-massive black hole (SMBH) growth, but this possible environmental effect remains unclear, largely due to the heterogeneous galaxy selections and active galactic nuclei (AGN) identification methods employed in previous studies.
In this talk, I will present the results of the first statistical study that quantitatively assess the impact of PC environment on SMBH growth and the physical mechanisms that drive the AGN enhancement in PCs relative to a homogeneously selected control sample of field galaxies. We find a statistically significant ($\approx3\sigma$) enhancement of X-ray AGN in PCs by $\approx3\times$ in excess to the field expectation. The field and PC galaxy samples are well matched in stellar mass, star-formation rate, and dust mass, indicating that the observed enhancement is not driven by selection effects or systematically higher host stellar masses. Our results provide quantitative and unbiased evidence that the dense PC environment enhances the AGN incidence beyond what is expected from host galaxy properties alone, likely through increased gas availability and interaction-driven fueling, allowing us to take a step forward toward a full understanding of the impact of the large-scale environment on SMBH and galaxy evolution.