Academia Sinica Logo

Abstract:

The intergalactic medium (IGM) around quasars is shaped by both their dense environments and excess ionizing radiation, forming a "quasar proximity zone" whose size and anisotropy depend on the quasar's age and radiation geometry. Using quasar pairs from the Dark Energy Spectroscopic Instrument (DESI) Year 1 data, we investigate how the foreground quasar's proximity zone affects Lyman-alpha absorption in the background quasar. The large DESI sample enables an unprecedented precision in measuring this effect, allowing a detailed investigation of the signal's dependence on the angular separation of quasar pairs and the luminosity of the foreground quasar. Our results reveal that enhanced gas clustering near quasars dominates over their ionizing effect, leading to stronger absorption on neighboring sightlines. We also model the hydrogen gas distribution and its connection to quasar luminosity, discussing implications for constraining quasar age and radiation geometry.