When I was in grad school, there were a lot of things we learned as “The universe is doing either this thing or this other thing,” as though the universe had to be limited in its options. One of those things was galaxy formation, which was described as either bottom-up or top-down, meaning either they formed through the merger of a lot of tiny systems or through the collapse of a massive cloud of gas and dust, to go from zero to a fully formed galaxy like Athena bursting from Zeus’s head.

We know at least our own galaxy formed hierarchically, through the build-up of small systems into the larger barred-spiral we enjoy today.

Other systems, we keep finding, do actually take another path, and observations taken of the elliptical galaxy C1-23152 show that this distant elliptical galaxy seems to have formed by the time the universe was just 1.8 billion years old. Data from the Large Binocular Telescope highlights massive amounts of star formation that took place during the galaxy’s first 500 million years, leaving it to evolve as a red dead system not too different from the elliptical galaxies we see in our modern universe.

This work is published in The Astrophysical Journal with first author Paolo Saracco. According to co-author Francesco La Barbera: These observations showed that the formation of the most massive galaxies in the Universe can occur extremely quickly, through an extremely intense star formation process in the early Universe, as for C1-23152. 

Co-author Adriana Gargiulo goes on to add: Understanding whether the scenario that describes the formation of C1-23152 is a particular case or whether, on the contrary, it is what happens for most of the most massive galaxies in the Universe is of fundamental importance since this would require a profound revision of the galaxy formation models.

Once again, the universe is telling us it’s not “either/or,” the answer is “and”.

More Information

LBTO news 

“The Rapid Buildup of Massive Early-type Galaxies: Supersolar Metallicity, High Velocity Dispersion, and Young Age for an Early-type Galaxy at z = 3.35,” Paolo Saracco et al., 2020 December 10, The Astrophysical Journal