This illustration depicts two quasars in the process of merging. There are many unanswered questions around galaxy mergers and the quasars that can result. Image Credit: NOIRLab/NSF/AURA/M. Garlick)
But quasars are mostly a thing of the past. Quasar activity seems to have peaked about 10 billion years ago, which is one reason there are still so many questions about how they form. “While multiwavelength observations of quasars have progressed significantly in recent years, understanding of their progenitors lags behind,” the authors write in their paper.
By observing the distribution and motion of hydrogen in the galaxies, the astronomers concluded that the pair is in the process of merging. Two pieces of evidence support their conclusion: the bridge of matter connecting them and the motion of the gas. Using ALMA, the researchers determined that the galaxies hold 100 billion solar masses of gas. That’s more gas than some of the galaxies that host the brightest quasars. This extraordinarily large amount of gas won’t be depleted quickly. It’s enough to trigger and sustain both explosive post-merger star formation and fuelling of the supermassive black hole.