The galaxies are already very large, with billions upon billions of stars orbiting supermassive black holes. But that’s not where their influence ends. The vast, spherical charge of gas surrounds the galaxy, reaching farther than the main population of stars, somewhat like the atmosphere of a galaxy.
Hubble observations from our nearest galactic neighbor, Andromeda, show how vast these halo los can get. According to a new analysis, the aerodynamic halo of the rome andromeda and the galaxy already touches 2.5-million-light-year space between stellar disks.
If we can see the halo of Andromeda in the night sky, it appears to be more than 100 times the apparent diameter of the full moon.
Impressions of the halo of Andromeda. (NASA, ESA, J. Deepasquel and E. Wheatley [STScI] And Z. Taken)
We can’t see, right – not with our own eyes. But Hubble is not so limited. And his new survey of the Andromeda halo has helped us understand the galaxy’s past, which in turn can help us understand how the galaxy evolved.
Understanding the vast accumulation of gas around the galaxy is very important, said Samantha Barrack, an astrophysicist at Yale University.
“This reservoir of gas contains the fuel for the formation of a future star inside the galaxy, as well as a stream of supernova-like phenomena.
The Andromeda Galaxy is much like a galaxy. They are both spiral galaxies. They are the same size and mass. The stars of both are relatively low (although the Milky Way is high).
We cannot easily interpret the halo of the galaxy, however, because, we are in it. So learning about the halo of Andromeda can give us insights into the hollows around our own galaxy.
The diffuse field of peripheral gas and plasma is very difficult to observe, so a team of researchers led by Nicholas Lehner, an astrophysicist at the University of Notre Dame, turned to distant quarters.
These are galactic nuclei that are highly active, emitting large amounts of radiation into space as their supermassive black holes consume huge amounts of matter – some of the brightest objects in the universe.
(NASA, ESA, and E. Wheatley / STSCI)
The ultraviolet light of the quarters near Andromeda in the night sky passes through the halo of Andromeda, some of which is absorbed by the gases in it. Using spectroscopic observations of this ultraviolet light using Hubble’s Cosmic Origins spectrograph, scientists can detect absorption features that reveal the presence of certain elements.
Previously, Lehman and his team used this method in six quarters to find out that the halo of Andromeda is much larger than we thought before.
They have now surveyed using qu 43 quarts, and found ionized gases of oxygen, silicon, and carbon in the space around Andromeda. By studying how this gas is distributed, they will not only map its extent, but also understand a structure.
Researchers have found that the halo is between 1.3 and 1.85 million light-years from the galaxy. In this halo, they discovered large amounts of heavy elements that were formed during supernova explosions, then blasted into space. And they found two different shells inside the halo, nesting inside each other.
“We get an inner shell that extends to about two million million light years, it’s more complex and dynamic,” Lehner said. “The outer shell is smooth and warm. This difference directly affects the inner halo from the effect of supernova activity in the galaxy’s disk.”
Quars have been used to investigate the Milky Way halo, but given the difficulty of interpreting the results, the value of such an exercise is limited. Now, however, Andromeda data can be used to refer to galaxy data, and can help us understand what we are seeing.
It could also help us better understand the galaxy merger, the early stages of which are still very mysterious. The Milky Way and Andromeda lead a merger in a few billion years, so it’s interesting to know that, through their halo, this merger has already begun.
“This is truly a unique experiment because with Andromeda alone we have information about its halo, not just with one or two views, but over 40,” Lehner said. “This is the basis for capturing the complexity of the galaxy halo beyond our own galaxy.”
Research has been published in Astrophysical Journal.
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