The early universe is a fascinating and mysterious place, filled with secrets waiting to be uncovered. One of the most intriguing puzzles astronomers have stumbled upon is the sudden cessation of star formation in some of the most massive galaxies in the early universe. These galaxies, known as massive quiescents (MQs), have stopped creating new stars just a billion years after they formed, which is a stark contrast to our own Milky Way, which is still producing stars at a slow but steady pace. This raises a deeper question: what is stopping these galaxies from forming stars?
In my opinion, the answer lies in the role of major galaxy mergers. These mergers, which are responsible for the growth of supermassive black holes and the resulting active galactic nuclei, can also trigger an extreme burst of star formation. However, the energy released by these mergers can also heat the surrounding halo gas, preventing it from cooling and being reincorporated into the galaxy. This, in turn, blocks the supply of raw material for new stars and halts star formation in less than a billion years.
What makes this particularly fascinating is the connection between MQs and dusty star-forming galaxies (DSFGs). These DSFGs are prolific star-formers, producing up to 500 solar masses of stars per year, compared to the Milky Way's one solar mass per year. However, they are cloaked in thick dust that blocks optical light, making them invisible to our telescopes. The researchers' new model, which produced a better match between the observed numbers of both MQs and DSFGs, suggests that most MQs first went through a phase as DSFGs. This implies that the progenitors of the vast majority of MQs are DSFGs, and that the most massive MQs were the brightest during their DSFG phase.
One thing that immediately stands out is the role of early mergers in the quenching of star formation in MQs. These mergers, which are responsible for the growth of supermassive black holes, can also trigger an extreme burst of star formation. However, the energy released by these mergers can also heat the surrounding halo gas, preventing it from cooling and being reincorporated into the galaxy. This, in turn, blocks the supply of raw material for new stars and halts star formation in less than a billion years.
From my perspective, the study of MQs and DSFGs is crucial for understanding the evolution of galaxies. By studying these extreme populations, we can gain insights into the physical processes driving the fuelling and quenching of star formation in the early universe. This, in turn, can help us build a more accurate understanding of the universe and its myriad interacting processes.
In conclusion, the premature quenching of star formation in MQs is a fascinating and complex phenomenon. By studying the role of major galaxy mergers and the connection between MQs and DSFGs, we can gain a deeper understanding of the universe and its evolution. As we continue to explore the early universe, I am excited to see what new insights and discoveries await us.
