2025/08/29 by Timo Kist, Joseph F. Hennawi, Kist, Timo +23
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics of Galaxies (astro-ph.GA) #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #Radio Astronomy Observations and Technology
paper · pdf · doi:10.48550/arxiv.2508.21818
openalex publication_date 2025/08/29 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/30
Thus far, Lyman-α damping wings towards quasars have been used to probe the global ionization state of the foreground intergalactic medium (IGM). A new parameterization has demonstrated that the damping wing signature also carries local information about the distribution of neutral hydrogen (HI) in front of the quasar before it started shining. Leveraging a recently introduced Bayesian JAX-based Hamiltonian Monte Carlo (HMC) inference framework, we derive constraints on the Lorentzian-weighted HI column density NHIDW, the quasar's distance rpatch to the first neutral patch and its lifetime tQ based on JWST/NIRSpec spectra of the two z ∼ 7.5 quasars J1007+2115 and J1342+0928. After folding in model-dependent topology information, we find that J1007+2115 (and J1342+0928) is most likely to reside in a ⟨ xHI ⟩ = 0.32-0.20+0.22 (0.58-0.23+0.23) neutral IGM while shining for a remarkably short lifetime of log10 tQ /yr = 4.14-0.18+0.74 (an intermediate lifetime of 5.64-0.43+0.25) along a sightline with log10 NHIDW /cm-2 = 19.70-0.86+0.35 (20.24-0.22+0.25) and rpatch = 28.9-14.4+54.0 cMpc (10.9-5.9+5.6 cMpc). In light of the potential presence of local absorbers in the foreground of J1342+0928 as has been recently suggested, we also demonstrate how the Lorentzian-weighted column density NHIDW provides a natural means for quantifying their contribution to the observed damping wing signal.