The First Stars, First Metals, and Second Stars

The universe formed with almost no elements other than Hydrogen and Helium. Because of this unique chemical composition, the stars that formed out of this gas were very different from the stars that formed today. They were likely much more massive and died violent and possibly quite exotic deaths. Their supernova explosions created the first heavy elements, which changed forever the way gas was able to collapse and form stars. I study how the next generation of stars formed amidst these first metals and how the process of star formation evolved to create the stars we observe today. Have a look here for some recent work I've done!

The Intergalactic Medium and the Missing Baryons

To observe the universe on large scales is to observe a sea of galaxies of many shapes and sizes. Yet, galaxies only make up about 10% of all normal matter (as opposed to dark matter.) The rest is distributed over the incredibly vast distances in between galaxies, comprising what is known as the intergalactic medium. The intergalactic medium is observable in the distant, and hence early, universe through the absorption of light by neutral Hydrogen. Adding up all of the observable matter (galaxies and the intergalactic medium) in the early universe yields a number that is consistent with other measurements of the total baryon (normal matter) content. However, a similar census performed in the local universe can only find roughly half of what should be there. Simulations, like the ones I run, have shown that these missing baryons are still in the intergalactic medium, but have been heated to temperatures too hot to be observable through absorption of Hydrogen. I use simulations to investigate how the intergalactic medium has evolved over the history of the universe and to search for ways in which these missing baryons might be detected.