January 17, 2021

They discover the mechanism that removes dark matter in galaxies


They discover the mechanism that removes dark matter in galaxies

They discover the mechanism that removes dark matter in galaxies

An international team of astronomers, in which researchers from the Canary Islands and Andalusia participate, has discovered that the tides caused by the gravitational interaction of a nearby galaxy is the mechanism that causes the elimination of dark matter in the galaxy NGC1052-DF4. Astronomers could not explain this lack of dark matter without breaking with accepted cosmological models, explains the Instituto de Astrofísica de Canarias (IAC).

Now, a team of researchers from the Instituto de Astrofísica de Canarias (IAC), the University of La Laguna (ULL), the University of New South Wales (Australia), the Instituto de Astrofísica de Andalucía (IAA-CSIC) and NASA has detected the mechanism that explains it: tides caused by the gravitational interaction of a nearby galaxy.

The finding, which is published in the scientific journal The Astrophysical Journal, reconciles this phenomenon with accepted models of galaxy formation and evolution. Astronomers have detected in NGC1052-DF4 profound changes in the distribution of matter due to tides caused by the gravitational interaction of a neighboring massive galaxy: NGC1035. According to the study, massive galactic systems can exert gravitational interaction on their neighboring galaxies, profoundly altering their structure to the point of destroying them.

These forces affect, at first, dark matter “since the stars are more concentrated and begin to be affected later, when the dark matter has practically been eliminated”, explains Mireia Montes, astrophysicist with a doctorate at the IAC, who Leading the research from the University of New South Wales, in Australia, what is observed is similar to what happens on Earth due to the gravitational forces exerted by the Moon.

“The mechanism was already known, but it had not been possible to observe in this type of galaxies, where the stellar density is extremely low,” says Ignacio Trujillo, astrophysicist at the IAC and one of those responsible for the work. And this is precisely what the study achieves: “detect features that are 1,000 times fainter than the night sky visible from Earth, in galaxies that are 65 million light-years from us,” adds Trujillo.

This type of research is known as “Science of low surface brightness” and, to obtain the images, those responsible have carried out a meticulous observation with the Hubble Space Telescope, the Gran Telescopio Canarias (GTC), at the Roque de los Muchachos Observatory (La Palma), and the IAC-80, from the Teide Observatory (Tenerife). But not in the traditional way, says the IAC, because although astronomers usually work with exposure times of half an hour, this work has required images of 60 hours of exposure, which “is quite complicated,” says Raúl Infante- Sainz, specialist in the analysis of low-brightness regions and another of those responsible for the work from the IAC.

And it is that, in addition to the time it takes to reach these very low star densities, then “you have to reduce the data in an adequate way to be able to obtain the low surface brightness structures, which are hidden below the noise level that they originally have. the images”.

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