Speaker
Description
Evolutionary scenarios predict that obscured quasars play a key role in the evolution of galaxies; however, this role has not yet been fully understood since quasar samples are typically biased against obscured systems. We select and constrain the AGN and host galaxy properties of a complete and unbiased sample of ~600 infrared (IR) quasars ($L_{\rm AGN,IR}>10^{45} \rm \:erg\: s^{-1}$) at $𝑧<3$, using spectral and photometric data from X-rays to radio wavelengths. We find that 61% IR quasars are obscured (55% are X-ray undetected) and identify fundamental differences in the average properties of obscured and unobscured quasars: 1) obscured quasars have star-formation rates ≈3 times higher, driven by a larger population of extreme starburst host galaxies, and 2) obscured quasars have stronger radio emission, potentially due to the interaction of jets or winds with a higher opacity circumnuclear medium (i.e., quasar “feedback”). Using ALMA submillimeter data, we then show that many of the obscured quasars are submillimeter galaxies, and that dust-obscured star-forming regions can produce extreme levels of obscuration ($N_{\rm H}\approx 10^{23}-10^{23} \rm \: cm^{-2}$), comparable to (or even dominate) the total quasar obscuration. These results challenge the standard AGN model as it fails to explain the AGN and host galaxy properties of obscured and unobscured IR quasars. I will finish my presentation introducing the 4MOST eROSITA/IR AGN survey, which will target $\sim$1M X-ray + $\sim$200,000 IR AGNs, and discuss how this large-scale survey will allow us to improve our understanding of the (non)evolutionary relationship between obscured-unobscured AGN and galaxies.
