Astroparticle Seminar

Optimizing global 21cm signal measurements with spectral and spatial information

Adrian Liu

MIT

Despite major advances in cosmology within the last few decades, there is still considerable uncertainty as to how the first luminous objects formed during the Epoch of Reionization (EoR). Measuring the 21cm line at the relevant redshifts has been shown to be a promising way to probe this era, at least in theory. In practice, such observations are difficult because the cosmological signals are expected not only to be extremely faint, but also to be contaminated by overwhelming bright foreground sources.

In this talk, I will focus on a particular flavor of 21cm experiments — the “global signal” measurements, where the 21cm signal is averaged over the entire sky and measured as a function of redshift. I will argue that is difficult (if not impossible) to mitigate foreground contamination without fine angular resolution, even though the ultimate goal is a signal averaged over the entire sky. Using a combination of simulations and analytic calculations, I will show that with the right data analysis/foreground subtraction techniques, an experiment with good angular resolution should be able to detect a cosmological 21cm signal at extremely high significance. This is encouraging news, for it suggests that even with severe foreground contamination, it should be possible to place interesting constraints on the EoR using global 21cm experiments.