Speaker
Description
Constraining the Epoch of Reionization remains one of the pivotal tasks of modern cosmology, and next-generation telescopes are opening up the path to the first precision constraints on the timing of reionization derived from the Lyman-$\alpha$ damping wing signature imprinted on the spectra of high-redshift quasars by the foreground neutral intergalactic medium (IGM). In the coming years, EUCLID will detect a number of high-redshift quasars never seen before, whose exquisite spectra collected by JWST will call for powerful statistical methods to infer precision constraints on the IGM neutral hydrogen (HI) fraction as a function of redshift.
We developed a state-of-the-art JAX-based Bayesian inference pipeline that allows us to disentangle the IGM damping wing from a quasar's unknown intrinsic spectrum, accounting for covariances across the full spectral range caused by IGM transmission fluctuations, quasar continuum reconstruction, and spectral noise. Besides the lifetime of the quasar, we infer a novel set of physical summary statistics that allows for a near-optimal extraction of the information carried by the Lyman-$\alpha$ damping wing about both timing and morphology of reionization. This comprises the HI column density within the first 100 cMpc from the quasar as well as the distance to the first neutral bubble before the quasar started shining. Besides constraining the global IGM neutral fraction, these statistics carry information about the morphology of reionization which currently remains unused in other state-of-the-art analysis frameworks.
After marginalizing out nuisance parameters associated with the quasar continuum, we find that we can constrain the HI column density within the first 100 cMpc of each individual quasar to 0.1 - 0.9 dex and its lifetime to 0.2 - 1.0 dex. By applying our procedure to a set of mock observational spectra resembling the distribution of EUCLID quasars with realistic spectral noise, we show that our method applied to upcoming observational data can robustly constrain the evolution of the IGM neutral fraction at the < 5% level at all redshifts between 6 < z < 11, and we present the first such constraints for high-z quasar spectra collected with JWST.
| Talk category | NOVA Network 1 |
|---|---|
| Preference for a talk or poster | Talk |
| Talk preference for PhD students | year 3 |
