How Early Galaxies Lit Up the Universe

OPEN TO THE PUBLIC | Dr. Anne Jaskot from Williams College will be joining for Science Workshop this week.

In the first billion years after the Big Bang, the Universe's hydrogen gas experienced a major transformation, switching from a neutral to an ionized state. We think that this event, known as “reionization”, was sparked by ultraviolet radiation escaping from early galaxies. However, we do not yet understand how such ionizing ultraviolet radiation escapes galaxies, and hence, we do not know which galaxies actually caused the reionization of the Universe. Part of the problem is that we cannot detect the ionizing light emitted by the early galaxies themselves; intervening gas destroys these photons on their ~12 billion year journey to Earth. Instead, we must observe nearby galaxies to learn which processes enable the escape of ionizing radiation. I will present results from a recent survey of nearby galaxies with the Hubble Space Telescope, which represents the largest sample to date of ionizing light measurements in nearby galaxies. This survey has given us new insights as to why ionizing light escapes some galaxies but not others and is helping us identify the galaxies responsible for cosmic reionization.