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The dance of the little galaxies surrounding the Milky Way

Credit: The Institute of Astrophysics of Canary IslandsAn international team led by IAC researchers used data from the Gaia ESA…



Credit: The Institute of Astrophysics of Canary Islands

An international team led by IAC researchers used data from the Gaia ESA satellite to measure the movement of 39 dwarf axes. These data provide information about the dynamics of these galaxies, their stories and their interactions with Winter Street.

Around the Milky Way there are many small galaxies, which can be tens of thousands of times or even millions of times less light than the Milky Way. In comparison to normal or giant galaxies, dwarf axes contain fewer stars and lower brightness.

These small galaxies have been the subject of the study by an international team of astronomers led by Tobias K. Fritz and Giuseppina Battaglia, both researchers of the Institute of Astrophysics of Canarias (IAC). Thanks to the data acquired by the ESA Gaia space mission, which became available in a second edition in April 201

8, researchers have been able to measure the cloud speech of 39 dwarf axes, determine direction and speed.

Before the second release of Gaia satellite data, it was not possible to perform such measurements for 29 of the galaxies analyzed by the team. The researchers found that many of them moved into a plane called the great polar structure. “It was already known that many of the more massive dwarf waxes were found in this plan, but now we know that even some of the less massive dwarf axes can belong to this structure,” said Fritz, lead author of the scientific article. 19659005] Battaglia emphasizes that the origins of the great polar structure are still not fully understood, but its properties appear to challenge cosmological models of galaxy formation. Stora Magellanic Cloud is also found in this planar structure, which may mean that the two are connected.

By analyzing data about the movements, the team found that several of the dwarf axes have paths that lead them close to the inner regions of Winter Street. The gravitational attraction that the Milky Way exerts on these galaxies can be compared to the effects of time. It is likely that some of the examined dwarf galaxies are disturbed by these tides, stretching them as a stream.

“This can explain observed features of some of these items, such as Hercules and Crater II,” says Fritz.

On the other hand, new questions arise. “Over the years, some galaxies have been observed to have special properties that may have been potentially due to tidal disturbances of the Milky Way (eg Carina I)”, says Battaglia. “But their paths seem not to confirm this hypothesis. Maybe we should postulate that meeting with other dwarf waxes could have been guilty.”

The researchers found that most of the galaxies studied are located near the pericentre of their orbits (the point closest to my winter street). Nevertheless, basic physics explains that they should spend most of their time near the pharmacy in its orbit (the point farthest away from the Milky Way). “This suggests that there would be many more dwarf axes that have not yet been discovered and are hiding a long distance from the Milky Way,” says Fritz.

In addition to being interesting, dwarf axes are one of the few traces of dark matter that can be used in the most outer parts of Winter Street. It is believed that this kind of matter accounts for about 80 percent of the universe’s total mass. However, it can not be observed directly, and detection is difficult. The movements of celestial body as dwarf axes can be used to measure the total mass of matter within a volume. This is determined by subtracting the mass of the shining objects detected to obtain an estimate of the amount of dark matter. From these data, the researchers can conclude that the amount of dark matter in the Milky Way is high, about 1.6 billion solar masses.


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More information:
T. K. Fritz et al. Gaia DR2 real movements of dwarf galaxies within 420 kpc, Astronomy & Astrophysics (2018). DOI: 10,1051 / 0004-6361 / 201833343

Journal Reference:
Astronomy & Astrophysics

Provided by:
Instituto de Astrofísica de Canarias

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