James Webb Space Telescope Feed Post

Date: 6/13/2024

Arxiv: Helium Reionization from Empirical Quasar Luminosity Functions before and after JWST Published: 4/9/2024 6:56:12 PM Updated: 6/12/2024 2:52:01 PM

Paper abstract: Recently, models of the quasar luminosity function (QLF) rooted on largeobservational compilations have been produced that, unlike their predecessors,feature a smooth evolution with time. This bypasses the need to assume anionizing emissivity evolution when simulating helium reionization withobservations-based QLF, thus yielding more robust constraints. We combine onesuch QLF with a cosmological hydrodynamical simulation and 3D multi-frequencyradiative transfer. The simulated reionization history is consistently delayedin comparison to most other models in the literature. The predictedintergalactic medium temperature is larger than the observed one at z <~3. Through forward modeling of the He II Lyman-\alpha forest, we show thatour model produces an extended helium reionization and successfully matches thebulk of the observed effective optical depth distribution, although itover-ionizes the Universe at z<~2.8 as the effect of small-scale LymanLimit Systems not being resolved. We thoroughly characterize transmissionregions and dark gaps in He II Lyman-\alpha forest sightlines. We quantifytheir sensitivity to the helium reionization, opening a new avenue for furtherobservational studies of this epoch. Finally, we explore the implications forhelium reionization of the large number of active galactic nuclei revealed atz\gtrsim5 by JWST. We find that such modifications do not affect anyobservable at z<=4, except in our most extreme model, indicating that theobserved abundance of high-z AGNs does not bear consequences for heliumreionization.