ALMA: Swirling Cool Jets Reveal Growing Supermassive Black Holes

The Atacama Large Millimeter/submillimeter Array (ALMA) has made another discovery.

In a study conducted by astronomers at Chalmers, they discovered a swirling jet of cool and dense gas in the center of a galaxy, 70 million light-years away from Earth. The swirling jets provides a clue to the mystery surrounding the growth of supermassive black holes.

The team of astronomers used ALMA to discover the jet of swirling cool gas in the center of galaxy NGC 1377 in the constellation Eridanus also known as the River. Their discovery was published in the journal of Astronomy and Astrophysics in June.

"We were curious about this galaxy because of its bright, dust-enshrouded center. What we weren't expecting was this: a long, narrow jet streaming out from the galaxy nucleus," Susanne Aalto, from the team said in a statement. Based on the study, the jet is almost 500 light-years long and less than 60 light years across, traveling at a speed of at least 800,000 kilometers per hour.

Astronomers have long been bewildered as to how black holes grow to their supermassive sizes. Most galaxies host a supermassive black hole in its center that ranges from a few million to a billion solar masses. How they grow is still a mystery until today. But using innovative telescopes, "accretion" or an event when a matter is directly falling into a black hole can be observed. Experts say that the cool jets are a typical sign that a black hole is growing through the process of accretion. But the swirling cool jets of gas from NGC 1377 tell the astronomers more.

"The jets we usually see emerging from galaxy nuclei are very narrow tubes of hot plasma. This jet is very different. Instead it's extremely cool, and its light comes from dense gas composed of molecules," Francesco Costagliola, co-author of the paper said in a statement published by Phys.Org.

Based on the observation of the astronomers, the jets ejected molecular gas in massive sizes equivalent to two million times the mass of the Sun in a relatively short time. This means the supermassive black hole being observed grows faster that expected. A team member on the study explained that black holes can grow by "accreting" hot plasma, but the black hole in NGC 1377 grow from the accretion of cold gas and dust and at a much faster speed.

Astronomers are still observing the behavior of swirling jets of cool gas by using ALMA. According to the team, the revolutionary capability of ALMA in measuring and detecting cold gas is vital in understanding galaxies and their accompanying central black holes.