Global cosmological signal detection experiments at radio frequencies

by Prof. Mayuri S Rao (Raman Research Institut)

Tuesday Mar 18, 2025, 11:00 AM → 12:00 PM Europe/Paris

Salle des séminaires (IAP)

Standard cosmology predicts inevitable signals that should be observable as global or all-sky signals. These include the additive distortions to the Cosmic Microwave Background (CMB) spectrum from photons emitted over the Epoch of Recombination. Another is the monopole signal from the redshifted 21-cm signal from hydrogen over the dark-ages, cosmic dawn, and epoch of reionization when the first stars and galaxies form. These signals can be detected at radio frequencies, but there has been no confirmed detection to date. Separating foregrounds, dominated by galactic emission, is a fundamental challenge to detection. Instrument properties, including the environment of operation of the instrument is yet another challenge. I will discuss two experiments from the CMB DISTORTION Lab at RRI, Bangalore with a primary goal to detect faint global cosmological signals. These are: PRATUSH - a proposed space based experiment to detect the global signal from the cosmic dawn in the lunar farside over 55-110 MHz; and APSERa - an upcoming experiment that will be custom built to make a precise measurement of the CMB spectrum over 2-4 GHz, study any excess radio emission over these frequencies, and eventually detect the faint spectral distortion from the epoch of recombination. I will also discuss instrument design and foreground separation methods that are used in these experiments.