Science & Technology

A mysterious substructure found in the outer disk of the Milky Way galaxy

The new map uses data from the Gaia Space Mission to reveal the new substructure of the outer disk of the Milky Way. Credit: C. Laporte et al. (MNRAS, 2021)

An international team of astronomers, led by researcher Chervin Laporte of the Institute of Space and Astronautical Science (ICCUB-IEEC), University of Barcelona, Milky WayExternal disc using data from the Gaia Space Mission.The survey results were published in the journal Monthly Notification of the Royal Astronomical Society..

“Usually this area of ​​the Milky Way has not been fully explored due to the presence of dust that severely obscures most of the galaxy’s midplane,” says Chervin Laporte, the first signer of the article. .. “Dust affects the luminosity of stars, but not the movement of stars. As a result, the movement of stars can be used to make tomographic images of the outermost regions of the galaxy.” ICCUB researchers add. The team analyzed Gaia motion data available from December 2020 to identify coherent structures.

This map shows that there are many previously unknown coherently rotating filamentous structures at the edges of the disc. It also provides a clearer global view of previously known structures. Numerical simulations predict that such filamentous structures will form in the outer disk from past satellite interactions, but the enormous amount of substructures revealed by this map are not expected. It remains a mystery.

Milky Way Galaxy Substructure

The new map uses data from the Gaia Space Mission to reveal the new substructure of the outer disk of the Milky Way. Credit: C. Laporte et al. (MNRAS, 2021)

What are these filamentous structures?

Our galaxy is surrounded by 50 satellite galaxies and has swallowed many galaxies in the past. It is now believed that the Milky Way is perturbed by the Sagittarius Dwarf Galaxy, a fact that supports Laporte’s early theoretical model. But in the distant past, it interacted with another intruder, Gaia Sausage. Gaia Sausage is now distributing its debris into stellar halos. Researchers hypothesized that these filamentous structures are the remnants of tidal arms from the Milky Way disk, which were excited at different times by different satellite galaxies.

In a previous study, Laporte found that one of the thread-like structures on the outer disk, called the Anticenter Stream, was primarily a star over 8 billion years old and “may be too old to cause.” Has already been shown. Sagittarius alone, but more consistent with the origin of the sausage. “Another possibility,” the researchers add. “Not all of these structures are actually real disc substructures, instead the illusion that the disc is highly substructured by forming the top of a vertical density wave on the disc seen in the projection. Form. “

The team secured a dedicated follow-up program using the WEAVE Spectrograph to study the similarities and differences between the star races in each substructure. Future studies WEAVE, SDSS-V, and PFS will also shed light on the origin of the substructure through studies of radial velocity, chemical abundance, and potentially stellar age.

Reference: “Kinematics defeats dust: reveals the nested substructure of the perturbed outer disk of the Milky Way,” Chervin FP Laporte, Sergey E Koposov, Vasily Belokurov, October 18, 2021. Monthly Notification of the Royal Astronomical Society: Letter..
DOI: 10.1093 / mnrasl / slab109



A mysterious substructure found in the outer disk of the Milky Way galaxy

https://scitechdaily.com/galaxys-edge-mystery-substructures-discovered-in-milky-ways-outer-disk/ A mysterious substructure found in the outer disk of the Milky Way galaxy

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