Coffee talks
Friday 08/05/2020 @ 11:00, Sala riunioni quarto piano
Emilio Ceccotti (Universita' di Bologna/INAF-IRA), "Upper limits on the 21 cm power spectrum from the Epoch of Reionization"
In my thesis, we analyzed observations taken with the Precision Array to Probe the Epoch of Reionization (PAPER) in the 120 ? 180 MHz range (i.e., 6 < z < 10) to estimate upper limits on the 21 cm power spectrum during the Epoch of Reionization (EoR), where the 21 cm line is one of the most promising probes of the intergalactic medium (IGM). The biggest challenge to 21 cm observations is the presence of Galactic and extragalactic foreground emission, which is a few orders of magnitude brighter. Foreground and 21 cm emissions can, however, be separated spectrally, as foreground emission is spectrally smooth on scales of tens of MHz, whereas the 21 cm emission significantly evolves on MHz scales. To remove the foreground contamination, we adopted a strategy that relies on avoidance, isolating the power spectrum region where the foreground emission is expected to be fainter than the EoR signal. We developed a pipeline to estimate the power spectrum of the 21 cm signal. In particular, the pipeline Fourier transforms visibilities along the frequency axis, confining foregrounds at low k-modes and leaving a contamination free window at higher k. In that window, we estimated upper limits on the 21 cm power spectrum and we calculated a preliminary lower limit on the IGM temperature at z = 7.48.