RSAA Colloquia / Seminars / Feast-of-Facts: Thursday, 08 October 2015, 11:00-12:00; Duffield Lecture Theatre

Neil Crighton

"Near Pristine Gas in the Early Universe"

The first stars, known as Population III, produced the first heavy elements, thereby enriching their surrounding pristine gas. However, all previous detections of metals in intergalactic gas clouds find a heavy element enrichment at least 1/1000 times that of the solar environment, which is higher than expected for remnants of Population III stars. In this talk I will describe our search for gas clouds with enrichment levels below this metallicity ’floor’ of 1/1000th solar, and outline the challenges involved in finding such systems and measuring their metallicity. Our search has discovered a cloud at redshift 3.5 with metallicity 1/2500th solar, the lowest value yet seen in a single cloud containing metals, and at the level expected for Population III remnants. I will discuss how relative abundance measurements in this extremely metal-poor regime enable us to test models of Population III star formation, early gas enrichment and metal mixing. Finally, I will summarise the prospects for finding similar systems in future surveys.