Research and projects

The Lyman-α forest in high-redshift quasars offers key insights into the late stages of the Epoch of Reionization (EoR), particularly through the presence of extended Gunn-Peterson troughs that suggest large-scale IGM structures. Using the XQR-30 dataset (5 < z < 6.1), the study investigates these large-scale correlations via a flux correlation matrix and MCMC modeling. Results show increasing correlation lengths with redshift, reaching up to ~250 cMpc at z = 6.1. Comparisons with large-volume simulations indicate that current models underpredict the observed correlations, pointing to a late reionization scenario and the need for larger simulations to capture the full spatial extent of IGM inhomogeneities.

The distribution, the size and the evolution of the last neutral hydrogen (H I) islands during the late stages of the Epoch of Reionization are still open to investigation. Additionally, Lyman-α emission detected in high-redshift galaxies imply they reside within large ionized bubbles which already exist at z > 10, raising questions on the rapid formation, merging, and expansion of these regions. By observing closely transverse paired high-redshift quasars, we aim to simultaneously address two objectives: (#1) mapping neutral H I regions in 3D to characterize the end of reionization and (#2) examining quasar-driven ionization bubbles, using the transverse proximity effect to measure quasar lifetimes and opening angles.

We report the first successful identification of the stochastic damping wings signal adjacent to Gunn-Peterson troughs at redshifts z=5.6 through careful stacking of the dark gaps in Lyman-a forest. We use the signal to present a measurement of the corresponding global HI fraction, and we found a lot of neutral hydrogen just at the end of the EoR, unequivocally signaling a late-and-slow reionization scenario. You can find our paper here. A couple of cool things about this project: this signal was predicted by Matthew Malloy and Adam Lidz almost 10 years ago and I can’t describe how excited I was to show Adam himself our results in Urbana; it was the first time this signal was detected, ever, we really couldn’t believe it! An independent team arrived at a similar conclusion, check Yongda Zhu work here.

When I joined Sarah’s group I ask to get involved in observational runs and well… I was not disappointed. I started following remotely LBT observations with the LUCI instrument and in September 2024 Sarah and I flown to Tucson (AZ), drove up to Mt. Graham and spend 6 nights observing the Arizona sky through the lens of MODS. During our last night there, Sarah asked me what I would do with MODS if I had time allocated and I replied I would look at pairs of close quasars to see how they would impact on each other spectra… long story short, our proposal to do it got accepted by the LBTB committee and observations are scheduled for next semester. Pretty cool ah?

I explored the too-often-forgotten reionization of helium, having the crazy idea we could use the 21cm analog for helium (at 3.46cm) to constrain such process. For this epoch, we currently lack strong constraints regarding its drivers and endpoint. We investigate the imprint of different reionization models (early, driven by quasars at high redshift z>5, and late, where active-galactic nuclei contribute from z=5) on the power spectrum of HeII mock intensity maps, forecasting for radio surveys. Unfortunately, the 3.46cm emission line is too faint to be detected in the near future.. it was still fun to try!