3:30–4:00 pm ERC 401
Insights into Co-evolution of Quasars and Their Host Galaxies from Wide-Separation Lensed Quasars
Advisor: Mike Gladders
The details of co-evolution between galaxies and their central supermassive black holes remain observationally elusive. Here, I explore the properties of a very rare sample of "wide-separation lensed quasars" (WSLQs), strongly lensed by massive galaxy clusters. Due to unparalleled magnification and distortion of host galaxy light, these WSLQ systems offer a spectacular opportunity for detailed study of galaxies hosting luminous quasars at z > 1, where we expect to find the strongest feedback processes. Using parametric models of surface brightness, measurements of broad quasar emission lines, and stellar population synthesis of the quasar host galaxies, I derive precise constraints on quasar and host galaxy properties for the current sample of known WSLQs. I then construct a statistical comparison between my WSLQ sample and other galaxies hosting active galactic nuclei (AGNs) at different cosmological epochs. Out of the 4 WSLQ hosts studied, 3 of them fall well below the star-forming main sequence, which may be consistent with the 'AGN feedback' hypothesis. Furthermore, I find that the WSLQ hosts are consistent with local (z ~ 0) measurements of the BH-mass–stellar-mass scaling relation, supporting a scenario of relatively concurrent mass assembly between central black holes and galaxies. This result is in tension with some recent papers in the literature, which find faster growth of black holes relative to galaxies at earlier times. As an additional test, I investigate systematics related to lens-modeling and model choices for star formation histories. Neither of these fully explain the discrepancy, as I again find consistency with the local scaling relation when accounting for intrinsic scatter in my stellar mass measurements. I stress that robust future studies of AGN–host co-evolution must account for systematics induced by SFH model choices, as these can significantly bias spectral energy distribution models. I anticipate that new facilities such as JWST and upcoming facilities in longer wavelengths will greatly assist in bypassing these biases, significantly improving our ability to probe co-evolution at higher redshift. This work demonstrates that WSLQs and highly magnified lensed quasars offer further exciting potential for co-evolution studies.