State of the Universe

Studying the end of Epoch of reionization with the 21-cm Signal

by Dr. Janakee Raste (TIFR-NCRA, Pune)

Friday, February 3, 2023 from to (Asia/Kolkata)
at A304 and Meeting ID: 825 1295 6967 Passcode: 384194
Recent constraints from Lyman-α and CMB data suggest a significantly delayed reionization scenario in which IGM is ionized to 50% at redshift z ~ 7. In these models, reionization ends at z ~ 5.3, with large “islands” of cold, neutral hydrogen persisting in the IGM well below z = 6.  We have studied these models using state-of-the-art radiative transfer simulations of the IGM calibrated to the CMB and Lyman-α forest data. In this talk, I will discuss effects of these neutral hydrogen islands on the 21cm signal. In contrast with previous models, we find that thanks to the late end of reionization, the 21cm power at z=5-6 predicted by our simulations is several orders of magnitude higher than that in conventional models considered in the literature for these redshifts. While the power spectrum is often the primary statistics to study the 21cm signal, these neutral islands are lowest density voids and are expected to be highly non-gaussian. With this motivation, I will also discuss the unique signature of these islands on the 21cm bispectrum signal. The delayed end of reionization moves the window of opportunity for the 21cm signal observation to higher frequencies, which will make the observational efforts easier due to easier thermal noise characteristics and synergies with abundant multi-wavelength observations.