May 14, 2021

A cosmic source in all its splendor

A cosmic source in all its splendor

A billion light years from Earth is one of the largest structures in the Universe: an enormous elliptical galaxy surrounded by an extensive cluster of galaxies known as Abell 2597. In the middle of the central galaxy there is a supermassive black hole that behaves like a great cosmic source, attracting large quantities of cold molecular gas and throwing it into space in a continuous flow.

Astronomers have long argued that sources of this type permanently recirculate the galactic fuel that feeds the birth of stars. The new Abell 2597 observations made with the Atacama Large Millimeter / submillimeter Array (ALMA) reliable indications of the existence of this flow of gas attracted and thrown by the supermassive black hole simultaneously. The researchers published their findings in the most recent edition of the Astrophysical Journal.

"The supermassive black hole located in the center of this giant galaxy acts as the mechanical pump of a water source ", explains Grant Tremblay, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics, in Cambridge, MA, USA. UU and main author of the article. "This is one of the first systems where clear evidence of the presence of an incoming stream of molecular gas and of jets thrown out or up through the black hole was found."

According to the researchers, the entire system operates through a self-regulated feedback loop. The attracted material provides energy to the source while it is "drained" into the black hole, like the water that enters the pump from a source. The entrance of this gas activates the black hole, which it throws jets of ultra-hot material at high speed out of the galaxy. On its journey, this material pushes out clouds and threads of gas towards the expanding halo of the galaxy, from where they end up flowing back into the black hole and triggering the whole process again.

In total, this source has molecular gas equivalent to about 3 billion solar masses, in a filamentary nebula that extends for the first 100,000 light years of the galaxy.

In a previous study published in the journal Nature, the same researchers were able to verify the interconnection of the black hole and the galactic source after observing the region at different wavelengths, or portions of the spectrum. By using ALMA to study the location and movement of carbon monoxide (CO) molecules, which emit a strong brightness at millimeter wavelengths, astronomers measured the movement of gas on its way to the black hole.

The data obtained previously by the MUSE spectroscopic scanner of the Very Large Telescope (VLT) of the ESO had shown warm ionized gas leaving the galaxy: it was, basically, the jet of the source. The new observations made with ALMA allowed to detect clouds of cold molecular gas precisely in the same places where warm gas had previously been observed.

"The unique aspect in this case was the extremely detailed analysis of this source using combined ALMA and UXO data. The two tools complement each other in an extraordinary way ", celebrates Tremblay. "ALMA revealed the distribution and movements of the cold clouds of molecular gas and MUSE did the same with the warm ionized gas."

The researchers note that the ALMA and UXO data were combined with a new ultra-deep observation of the cluster with NASA's Chandra X-ray observatory, revealing with exquisite detail the hot phase of the source.

The observations also strongly support the hypothesis that warm ionized gas and cold molecular gas nebulae they are part of the same structure, where the ionized gas is nothing more than the "shell" of the cold molecular nuclei swirling within this galactic source.

This multi-wavelength analysis method offers an unusually complete picture of the system. "It's like watching the cloud, the rain and the puddle at the same time," says Tremblay. Although these observations correspond to a single galaxy, astronomers believe that this process could be common in other galaxies and fundamental for its evolution.


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