Illuminating the Cosmic Dawn with Sky-Average Radio Measurements
Abstract: Obtaining direct measurements of the period when the first compact sources formed is one of the challenges of modern cosmology. At redshifts > 6, before and during the epoch of reionization (EoR), UV and X-ray radiation from the first galaxies and black holes altered the energy state of the neutral hydrogen in the intergalactic medium (IGM) and imprinted features in the otherwise smooth evolution of the IGM's physical and spin temperatures. In this talk I will describe how we can use sky-average, or global, measurements of the low-frequency (< 200 MHz) radio sky to detect these features. Precise characterization of these features would enable us to derive properties of the galaxies and black holes through Cosmic Dawn and the EoR. The talk will focus on recent measurements and progress by the Experiment to Detect the Global EoR Signature (EDGES). EDGES measures the sky-average radio spectrum from the Murchison Radio-astronomy Observatory in Western Australia and is already placing exciting constraints on the properties of the first compact objects in the Universe.