A group of astrophysicists led by Mireia Montes, a researcher at the Astronomical Institute of Canarias (IAC), has discovered the largest and most diffuse galaxy ever recorded.The study was published in the journal astronomy and astrophysicsusing data taken by the Gran Telescopio Canarias (GTC) and the Green Bank Radio Telescope (GBT).
Nube is a nearly invisible dwarf galaxy discovered by an international research team led by the Institute of Astronomy of Canarias (IAC) in collaboration with the University of La Laguna (ULL) and other institutions.
The name was suggested by the 5-year-old daughter of one of the group’s researchers and derives from the object’s diffused appearance. Its surface brightness is so faint that previous surveys of this part of the sky have passed it by unnoticed, as if it were some kind of ghost. This is because the star is so massively spread out that the “nube” (Spanish for “cloud”) is almost undetectable.
This newly discovered galaxy has a set of specific properties that distinguish it from previously known objects. The researchers estimate that Nube is a dwarf galaxy that is 10 times fainter than other galaxies of its type, but extends 10 times longer than other objects with similar star counts. To explain what this means to those who know a little astronomy, this galaxy is one-third the size of Earth’s. milky waybut its mass is similar to the Small Magellanic Cloud.
“With our current knowledge, we cannot understand how galaxies with such extreme features could exist,” said Mireia Montes, lead author of the paper and a researcher at IAC and ULL. explains.
Ignacio Trujillo, the second author of this article, has been conducting analyzes based on SDSS images for several years (Sloan Digital Sky Survey), a certain empty strip in the framework of the project Legado del IAC Stripe 82. During one of my data revisions, I noticed a faint speck that seemed interesting enough to launch a research project.
The next step was to use ultra-deep polychromatic images from the Great Canary Telescope (GTC) to confirm that this patch in the survey was not some kind of error, but rather a very diffuse object. Nube is so dark that it is difficult to gauge the exact distance. The authors estimated Nube’s distance to be 300 million light-years, using observations made with the Green Bank Telescope (GBT) in the United States, as well as observations with the Very Large Array (VLA) radio telescope and the optical William Herschel Telescope. (WHT) at the Roque de los Muchachos Observatory on La Palma should help show whether this distance is correct. “Even if the galaxy turns out to be much closer, it will still be a very strange object and pose a big challenge to astrophysics,” comments Ignacio Trujillo.
A new challenge to the current dark matter model?
The general law is that in the inner regions of galaxies the density of stars is much higher, and this density decreases rapidly as the distance from the center increases. However, Montes said that in Nube, “there is very little change in star density across the object, which is why it is so faint, and we could not see it well until we got ultra-deep images from the GTC.” Masu. ”
Nube is puzzling astronomers. Just in case, the research team explains that there are no interactions or other indications of its strange properties. Cosmological simulations cannot reproduce its “extreme” properties, even based on different scenarios. “Within the currently accepted cosmological model, namely cold dark matter, a viable explanation remains elusive,” Montes explains.
Although cold dark matter models can reproduce the large-scale structure of the universe, they may not provide adequate answers in small-scale scenarios, such as in the case of Nube. We show how different theoretical models fail to generate it, making this one of the most extreme cases known to date. “This galaxy, and any similar galaxies we may discover, may provide additional clues that open new windows into our understanding of the universe,” Montes said.
“One attractive possibility is that Nube’s unusual properties indicate that the particles that make up dark matter have extremely low masses,” says Ignacio Trujillo. If so, the galaxy’s unusual properties would demonstrate the properties of quantum physics on a galactic scale. “If this hypothesis is confirmed, it would be one of nature’s most beautiful demonstrations of the union of the smallest and largest worlds,” he concluded.
References: “A nearly dark galaxy with the mass of the Small Magellanic Cloud” Mireia Montes, Ignacio Trujillo, Ananthan Karunakaran, Raul Infante Sainz, Christine Speckens, Julia Golini, Michael Beasley, Maria Cebrian, By Nushkia Chamba, Mauro D’Onofrio, Lee Kelvin and Javier Roman, January 9, 2024. astronomy and astrophysics.
DOI: 10.1051/0004-6361/202347667