An unusual discovery about satellite galaxies

According to RCO News Agency, The SAGA project is being conducted by a small group of astronomers to find out how the Milky Way and its small cluster of dwarf satellite galaxies compare to other galactic systems.

According to Spacey, Marla Geha, a professor of astronomy and physics at Yale University and one of the founders of the SAGA project, said: The Milky Way’s satellite population is a unique combination of small satellite galaxies that contain only older stars. and two large satellite galaxies that are actively forming new stars.

These two large satellite galaxies are the Large and Small Magellanic Clouds, abbreviated as LMC and SMC. These two satellite galaxies are the largest examples of their kind in the Milky Way family and can be easily seen with the naked eye from the southern hemisphere. Most of the other 59 satellite galaxies of the Milky Way are very faint and require the Hubble Space Telescope or large ground-based telescopes to detect them.

The SAGA project conducted a census of 101 galaxies similar in size and mass to the Milky Way, hosting a total of 378 satellite galaxies. The number of visible satellite galaxies in each host galaxy varied from zero to 13.

Yao-Yuan Mao, a researcher at the University of Utah (U of U) and one of the founders of SAGA said: If you consider the existence of the Large Magellanic Cloud, the Milky Way seems to host fewer satellite galaxies because the process What SAGA discovered is that if at least one Magellanic-type galaxy orbits the host galaxies, the host galaxies generally have more satellite galaxies.

However, non-Magellanic-type galaxies have fewer satellites. One explanation is that the Magellanic Clouds are a recent addition to the Milky Way family. For example, a 2007 study by Gurtina Besla of the Steward Observatory in Arizona showed that the Magellanic Clouds are the first visitors to the galaxy’s gravitational trap in the past three billion years. milk fell Therefore, based on the trend observed by SAGA, the Milky Way was not expected to have bright satellite galaxies before the arrival of the Magellanic Clouds. It is assumed that other Magellanic-type galaxies have formed in other systems around their host galaxy.

Additionally, Magellanic galaxies themselves are extremely rare. A 2012 study led by University of Western Australia (UWA) researcher Aaron Robotham showed that only three percent of spiral galaxies similar to the Milky Way have examples of the Magellanic Cloud.

Astronomers have learned more about dwarf satellite galaxies in the latest data from SAGA. For example, they found that the closer a satellite galaxy is to its host galaxy, the more likely the satellite’s star formation rate is zero or close to it. The closer a satellite galaxy is to its host galaxy, the deeper it sinks into the host’s gravitational hole and dark matter halo, and the closer it is to all the radiation emitted by hot, young stars or supernova explosions that can eject star-forming gas from an orbiting satellite galaxy. is

Astronomers call the cessation of star formation in a galaxy a “quenching,” and the SAGA findings directly link the quenching to the environment around the host galaxy. Most of the Milky Way’s satellite galaxies are quenched, and at least in part the reason they are so dim is that they haven’t been able to form many stars. Also, the SAGA results suggest that quenched galaxies should be in more isolated environments, rather than in systems full of other satellite galaxies that could interact with them and stimulate further star formation.

Dwarf satellite galaxies exist in the large halo of dark matter that surrounds all large galaxies. This halo acts as a gravitational framework for the formation of galaxies. Dwarf galaxies are the building blocks of their host galaxies. The hierarchical model of galaxy formation described by the Standard Model of Cosmology, in which larger galaxies form from smaller galaxies, predicts that there should actually be more dwarf satellite galaxies around the Milky Way than are currently recognized. .

Where the missing galaxies are still a mystery, but by sampling and studying dwarf galaxies around other galaxies, scientists can learn about the dark matter halos around other galaxies, how they affect galaxy formation and evolution, and where small satellite galaxies are hiding.

This research was published in “The Astrophysical Journal”.

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