The Hot Building Blocks of Galaxies

The formation of the first stars was the last watershed moment in our Universe.

They produced the first ionizing radiation since recombination, all elements heavier than lithium, and initiated the last phase transition (cosmic reionization). For decades, theory has posited that these stars are very unlike those forming today.

They live and die in extremely dense environments, become Super Massive Stars (SMS) through runaway mergers, and collapse to form the first black holes.

They burn hotter than their modern counterparts, produce more ionizing radiation, and may probably play a key role in reionization.Today only 4 galaxies are known to host SMSs and we know little of their contribution to the early Universe.

Their spectral signatures are very weak and unique to the ultraviolet: they can only be identified in the brightest galaxies and only with JWST.

Progress is slow because JWST’s main modes are not optimized to study these features, but we show here that they lie just below the current observational threshold.

Our team has designed a new creative observing technique to identify SMS signatures directly in survey data, and is executing a 50-hour JWST campaign to find them.

We request funding to (1) develop the new observing mode that could triple the spectroscopic efficiency of JWST, and (2) exploit this survey to determine the abundance of Super Massive Stars at early times. We will measure their ionizing outputs, chemical yields, and influence on the early Universe.