Quasars might inhibit star formation in galaxies

Artist's concept of the dusty starburst galaxy WISE J224607.57-052635.0 (Image NASA/JPL-Caltech)
Artist’s concept of the dusty starburst galaxy WISE J224607.57-052635.0 (Image NASA/JPL-Caltech)

An article published in “The Astrophysical Journal” describes a research suggesting that in primeval galaxies of the type called dusty starburst – because dust filters their light – star formation activity can be inhibited by the presence of a quasar. A team of astronomers from Iowa University used the ALMA radio telescope to locate the quasars and then other telescopes to observe them at various wavelengths.

When the universe was young, there were galaxies where star-forming activity was at its peak and those are called starburst galaxies. Some of them, however, were full of dust capable of absorbing electromagnetic emissions at many wavelengths generated inside them and are therefore called dusty starburst galaxies. This characteristic made it difficult to understand why some of these galaxies turned from star incubators at ever-seen levels in the history of the universe into cosmic graveyards.

The possibility to use the ALMA (Atacama Large Millimeter/submillimeter Array), which was inaugurated in March 2013, allowed to get details of areas of the cosmos that years ago was really difficult if not impossible to study. In this case, astronomers could locate in a dusty starburst galaxy a quasar, a galactic nucleus that is extremely bright due to a supermassive black hole surrounded by a ring of materials falling towards it, generating very high levels of electromagnetic radiation

The astronomers focused on four quasars in the galaxies observed when they were still producing stars. In the case of galaxies that are 12 billion light years away, even ALMA works at the limits of its possibilities despite being the most powerful radio telescope currently in activity. This means that it allowed to locate quasars surrounded by dust but without getting details of those areas.

In fact, even with ALMA at least in some cases it should be impossible to see quasars because their light should be completely absorbed or at least blocked by dust. According to the astronomers who conducted this research it’s possible that all dusty starburst galaxies have quasars at their center that are not visible from the outside.

The fact that some quasars are visible could mean that their electromagnetic emissions escape their galaxies through a dust-free region. This may depend on the orientation of the galaxy relative to Earth and of the resulting amount of dust present between the quasar at its center and the Earth.

The presence of a quasar is important because according to astronomers who conducted this research, the enormous energy of the supermassive black hole drives the gas needed to form new stars out of the galaxy. Curiously, in May 2017 an article published in the journal “Nature” described the observation of primeval galaxies with an extremely high stellar formation rate close to quasars.

It’s not surprising to see that quasars have effects on the galaxies that host them, a little more on nearby galaxies but they’re extremely energetic objects so their influence can extend to really huge areas. Instruments such as ALMA allow to observe that influence and better understand its possible consequences.

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