Massive galaxy sucks back recycled gas to form new stars

How the study was conducted?

In 2017, a team of scientists from Tsinghua University in Beijing spotted this mysterious MAMMOTH-1 nebula. After this discovery, they conducted follow-up observations with ground-based telescopes, including Keck and Subaru, in Hawaii. 

This strange galaxy behavior was noted in these observations. The images revealed that it devoured material from its surroundings via at least three gas sources in the cosmic web. Two of these gas streams are likely to have come from a quasar, which is a luminous celestial object fueled by a supermassive black hole.  

To get a better picture, the team used spectra instruments mounted on telescopes to try to understand the composition of the gas surrounding the nebula. 

Carbon was abundant in the gas streams that surrounded the nebula. However, previous simulations indicated that this gas should primarily consist of leftover hydrogen from the big bang.

As per the study, the presence of an active galactic recycling system is indicated by the abundance of carbon. This metal-enriched gas would have cooled faster, resulting in the birth of a new generation of stars. 

Typically, the gas reservoirs that surround galaxies, known as the circumgalactic medium (CGM) and intergalactic medium (IGM), fuel their evolution. This stellar gas eventually condenses to form stars.

The official statement explains, “Simulations and observations have shown that cold stream accretion – the accumulation of pristine intergalactic gas that contains almost no elements heavier than helium – provides fuel for the star formation rate of galaxies in the early Universe.” 

It further adds, “However, stellar processes in these early galaxies, such as supernovae, enrich gas within the galaxy with elements heavier than helium, including carbon. Related processes can even eject some of this material back out into the IGM. Theory predicts that the enriched gas could subsequently be recycled, accreting back into galaxies, providing additional fuel to sustain rapid star formation for longer. “

The study is published in the journal Science.

Study abstract:

Stars form in galaxies, from gas that has been accreted from the intergalactic medium. Simulations have shown that recycling of gas—the reaccretion of gas that was previously ejected from a galaxy—could sustain star formation in the early Universe. We observe the gas surrounding a massive galaxy at redshift 2.3 and detect emission lines from neutral hydrogen, helium, and ionized carbon that extend 100 kiloparsecs from the galaxy. The kinematics of this circumgalactic gas is consistent with an inspiraling stream. The carbon abundance indicates that the gas had already been enriched with elements heavier than helium, previously ejected from a galaxy. We interpret the results as evidence of gas recycling during high-redshift galaxy assembly.