The Astrophysical Journal • Vol 985 • No 1
Probing the He <scp>ii</scp> re-Ionization ERa via Absorbing C <scp>iv</scp> Historical Yield (HIERACHY). II. Project Design, Current Status, and Examples of Initial Data Products
May 2025 • Jiangtao Li, Xiaodi Yu, Huiyang Mao, Hanxiao Chen, Tiancheng Yang, Zhijie Qu, Fuyan Bian, Joel N. Bregman, Zheng Cai, Xiaohui Fan, Taotao Fang, Ji Li…
Abstract The He ii reionization epoch is expected to take place at z ∼ 3–5. In this stage, the helium and metals in the intergalactic medium are further ionized with additional contributions from harder nonstellar sources, and some large-scale gravitationally bound systems approach virialization. The Probing the He ii re-Ionization ERa via Absorbing C iv Historical Yield (HIERACHY) program utilizes high- and medium-resolution spectra of bright background quasars at z ≈ 3.9–5.2 to investigate Ly α , C iv , and othe…