The Milky Way’s small satellite galaxy is extremely rare, a new 12-year study of other galaxies in the local universe has found.
The Galactic Analog Satellite (SAGA) survey is being conducted by a small group of astronomers to learn how galactic analogs occur. milky way and a small retinue of dwarf satellites galaxy Compare with other galaxies.
“The Milky Way galaxy’s satellite constellation is a unique combination of small satellites, including only older satellites. starand its two largest moons are actively forming new stars,” said Mara Geha, professor of astronomy and physics at Yale University and co-founder of SAGA. I am. statement.
These two largest satellites are big and small magellanic cloudknown as LMC and SMC for short. These two moons are by far the largest in the Milky Way galaxy and are easily visible to the naked eye from the Southern Hemisphere. Most of the Milky Way’s other 59 known satellite galaxies are very faint; hubble space telescope Or large telescopes on the ground to detect them.
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SAGA conducted a census of 101 galaxies similar in size and mass to the Milky Way, for a total of 378 satellite galaxies. The number of visible satellite galaxies per host galaxy ranged from 0 to 13. This is compared to the Milky Way galaxy. dark energy The Mayall Telescope Spectrometer (DESI) at Kitt Peak National Observatory in Arizona was able to detect only four satellites. The remaining moons in our galaxy are too faint for DESI to see.
“Given the presence of the LMC, the Milky Way appears to have fewer satellites,” Yao-Yuan Mao of the University of Utah and co-founder of SAGA said in the paper. statement.
That’s because, as discovered by SAGA, host galaxies generally tend to feature more satellite galaxies when they orbit at least one Magellanic-type galaxy.
However, galaxies that do not have the Magellanic type tend to have fewer satellites. One explanation is that the Magellanic Clouds are recent additions to the Milky Way. For example, a 2007 study by Glutina Besra, now at the Steward Observatory in Arizona, found that the Magellanic Clouds I’m a first time visitorcaptured by the Milky Way’s gravity and trapped in orbit over the past 3 billion years. Therefore, based on the trends observed by SAGA, the Milky Way would not have been expected to have so many bright satellite galaxies before the arrival of the Magellanic Clouds. It is hypothesized that other Magellanic-type galaxies in other systems have formed around the host galaxy.
Furthermore, Magellanic-type galaxies are themselves extremely rare. Previous research in 2012 led by Aaron Robotham at the University of Western Australia, as part of the Galaxy and Mass Assemblies (GAMA) survey, concluded Only 3% of spiral galaxies similar to the Milky Way have Magellanic Cloud-type moons.
In the final data release from SAGA (the first two batches of data from the project were produced in 2017 and 2021), astronomers also learned other things about dwarf satellites. For example, researchers found that the closer a satellite galaxy is to its host galaxy, the more likely the satellite’s star formation rate is at or near zero. The closer a satellite is to its host galaxy, the deeper it becomes trapped within its host’s gravitational well. dark matter The closer it gets to the halo and the hot, young stars and radiation poured by them, the more supernova The explosion could remove star-forming gas from orbiting satellite galaxies.
Astronomers refer to the cessation of star formation within a galaxy as “quenching,” and SAGA’s discovery directly links extinction to the host galaxy’s surrounding environment. Most of the Milky Way’s satellite galaxies have been quenched, which is, at least in part, why the galaxy is so dark. This is because galaxies are not able to form many stars. The SAGA results also suggest that the quenched galaxies should be in more isolated environments, rather than in dense systems with other potentially interacting satellite galaxies, encouraging more star formation within the galaxy. It also suggests that.
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But what does this actually mean? Dwarf satellite galaxies exist within a huge halo of dark matter that surrounds all large galaxies. This halo acts as a gravitational scaffold for the formation of these galaxies. Dwarf galaxies are components of larger host galaxies. The hierarchical galaxy formation model described in the Standard Model of Cosmology, in which larger galaxies are assembled from smaller galaxies, suggests that there are actually many more dwarf moons around the Milky Way than currently detected. It is predicted that it should. Where these missing galaxies are located remains a mystery, but by sampling and studying dwarf galaxies around other galaxies, dark matter halos around other galaxies, galaxy formation, and You can learn about their influence on evolution and where small satellite galaxies are hiding.
There are three new research papers describing SAGA’s findings, led by Geha, Mao and Lisa Wexler of Stanford University in California. The paper has been accepted for publication in The Astrophysical Journal and is currently available as a preprint. Anomaly of the Milky Waya paper led by Geha satellite quenchingand for the third paper. Data modeling.
