Studying star formation in the early universe can give us clues about what the universe was like when the earliest massive galaxies were forming. How efficiently were these first galaxies making stars only a billion years after the Big Bang?
Lighting Up the Universe
The universe wasn’t always a treasure trove of galaxies. Not long after the Big Bang, it consisted largely of opaque neutral hydrogen, and the only photons present were either from the cosmic microwave background or emitted during electron transitions in hydrogen atoms. Between redshifts of z = 20 and z = 6 (i.e., between 150 million and 1 billion years after the Big Bang), the first galaxies formed and their stars ionized the hydrogen, allowing light to travel freely through the universe.
This sounds very neat and straightforward, but the specifics of this process are hazy (note the very large time window!). What sort of stars did the ionizing? Did it happen all at once or more slowly? How long did it take? Pinning down the star formation rates of galaxies at that transition redshift of z ~ 6 can help us answer some of these questions.
Left: spectra of galaxies HZ10 and LBG-1 highlighting ...