Giant Halo Around Andromeda Galaxy Mapped by Hubble in Landmark Study

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Andromeda Galaxy Gaseous Halo

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This illustration portrays the gaseous halo of the Andromeda galaxy if it might be seen with the naked eye. At a range of 2.5 million light-years, the magnificent spiral Andromeda galaxy is so near to us that it looks like a cigar-shaped spot of light high in the fall sky. If its gaseous halo might be seen with the naked eye, it would have to do with 3 times the width of the Big Dipper—quickly the greatest function on the nighttime sky. Credit: NASA, ESA, J. DePasquale and E. Wheatley (STScI), and Z. Levay (background image)

In a landmark research study, researchers utilizing NASA’s Hubble Space Telescope have actually mapped the enormous envelope of gas, called a halo, surrounding the Andromeda galaxy, our closest big galactic next-door neighbor. Scientists were amazed to discover that this rare, almost unnoticeable halo of diffuse plasma extends 1.3 million light-years from the galaxy—about midway to our Milky Way—and as far as 2 million light-years in some instructions. This indicates that Andromeda’s halo is currently running into the halo of our own galaxy.

They likewise discovered that the halo has a layered structure, with 2 primary embedded and unique shells of gas. This is the most thorough research study of a halo surrounding a galaxy.

“Understanding the huge halos of gas surrounding galaxies is immensely important,” discussed co-investigator Samantha Berek of Yale University in New Haven, Connecticut. “This reservoir of gas contains fuel for future star formation within the galaxy, as well as outflows from events such as supernovae. It’s full of clues regarding the past and future evolution of the galaxy, and we’re finally able to study it in great detail in our closest galactic neighbor.”

“We find the inner shell that extends to about a half million light-years is far more complex and dynamic,” discussed research study leader Nicolas Lehner of the University of Notre Dame in Indiana. “The outer shell is smoother and hotter. This difference is a likely result from the impact of supernova activity in the galaxy’s disk more directly affecting the inner halo.”

A signature of this activity is the group’s discovery of a big quantity of heavy aspects in the gaseous halo of Andromeda. Heavier aspects are formulated in the interiors of stars and after that ejected into area—in some cases strongly as a star passes away. The halo is then polluted with this product from outstanding surges.

The Andromeda galaxy, likewise called M31, is a stunning spiral of maybe as numerous as 1 trillion stars and equivalent in size to our Milky Way. At a range of 2.5 million light-years, it is so near to us that the galaxy looks like a cigar-shaped spot of light high in the fall sky. If its gaseous halo might be seen with the naked eye, it would have to do with 3 times the width of the Big Dipper. This would quickly be the greatest function on the nighttime sky.

Through a program called Project AMIGA (Absorption Map of Ionized Gas in Andromeda), the research study took a look at the light from 43 quasars—the extremely remote, fantastic cores of active galaxies powered by great voids—situated far beyond Andromeda. The quasars are spread behind the halo, enabling researchers to penetrate numerous areas. Looking through the halo at the quasars’ light, the group observed how this light is taken in by the Andromeda halo and how that absorption modifications in various areas. The enormous Andromeda halo is made from extremely rarified and ionized gas that doesn’t release radiation that is quickly noticeable. Therefore, tracing the absorption of light originating from a background source is a much better method to penetrate this product.

Andromeda Halo 43 Quasars

This illustration reveals the place of the 43 quasars researchers utilized to probe Andromeda’s gaseous halo. These quasars—the extremely remote, fantastic cores of active galaxies powered by great voids—are spread far behind the halo, enabling researchers to penetrate numerous areas. Looking through the enormous halo at the quasars’ light, the group observed how this light is taken in by the halo and how that absorption modifications in various areas. By tracing the absorption of light originating from the background quasars, researchers have the ability to penetrate the halo’s product. Credit: NASA, ESA, and E. Wheatley (STScI)

The scientists utilized the distinct ability of Hubble’s Cosmic Origins Spectrograph (COS) to study the ultraviolet light from the quasars. Ultraviolet light is taken in by Earth’s environment, that makes it difficult to observe with ground-based telescopes. The group utilized COS to find ionized gas from carbon, silicon, and oxygen. An atom ends up being ionized when radiation strips several electrons from it.

Andromeda’s halo has actually been penetrated prior to by Lehner’s group. In 2015, they found that the Andromeda halo is big and huge. But there was little tip of its intricacy; now, it’s drawn up in more information, causing its size and mass being much more properly identified.

“Previously, there was very little information—only six quasars—within 1 million light-years of the galaxy. This new program provides much more information on this inner region of Andromeda’s halo,” discussed co-investigator J. Christopher Howk, likewise of Notre Dame. “Probing gas within this radius is important, as it represents something of a gravitational sphere of influence for Andromeda.”

Because we live inside the Milky Way, researchers cannot quickly translate the signature of our own galaxy’s halo. However, they think the halos of Andromeda and the Milky Way should be extremely comparable because these 2 galaxies are rather comparable. The 2 galaxies are on a clash, and will combine to form a huge elliptical galaxy starting about 4 billion years from now.

Scientists have actually studied gaseous halos of more remote galaxies, however those galaxies are much smaller sized on the sky, indicating the variety of intense sufficient background quasars to penetrate their halo is typically just one per galaxy. Spatial info is for that reason basically lost. With its close distance to Earth, the gaseous halo of Andromeda looms big on the sky, permitting a much more substantial tasting.

“This is truly a unique experiment because only with Andromeda do we have information on its halo along not only one or two sightlines, but over 40,” discussed Lehner. “This is groundbreaking for capturing the complexity of a galaxy halo beyond our own Milky Way.”

In reality, Andromeda is the only galaxy in deep space for which this experiment can be done now, and just with Hubble. Only with an ultraviolet-sensitive future area telescope will researchers have the ability to consistently undertake this kind of experiment beyond the roughly 30 galaxies making up the Local Group.

“So Project AMIGA has also given us a glimpse of the future,” stated Lehner.

The group’s findings appear in the August 27 edition of The Astrophysical Journal.

Reference: “Project AMIGA: The Circumgalactic Medium of Andromeda” by Nicolas Lehner, Samantha C. Berek, J. Christopher Howk, Bart P. Wakker, Jason Tumlinson, Edward B. Jenkins, J. Xavier Prochaska, Ramona Augustin, Suoqing Ji, Claude-André Faucher-Giguère, Zachary Hafen, Molly S. Peeples, Kat A. Barger, Michelle A. Berg, Rongmon Bordoloi, Thomas M. Brown, Andrew J. Fox, Karoline M. Gilbert, Puragra Guhathakurta, Jason S. Kalirai, Felix J. Lockman, John M. O’Meara, D. J. Pisano, Joseph Ribaudo and Jessica K. Werk, 27 August 2020, The Astrophysical Journal.
DOI: 10.3847/1538-4357/aba49c

The Hubble Space Telescope is a job of global cooperation in between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, handles the telescope. The Space Telescope Science Institute (STScI) in Baltimore carries out Hubble science operations. STScI is run for NASA by the Association of Universities for Research in Astronomy, in Washington, D.C.



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