The position of the newly found dwarf galaxy (Virgo III) in the constellation Virgo (left) and its member stars (right; those circled in white). The star members are centered inside the dashed line in the right panel. Credit: NAOJ/Tohoku University
For years, astronomers have puzzled over how to explain why the Milky Way has fewer satellite galaxies than the standard dark matter model predicts. This is called the “missing satellites problem”.
To bring us closer to solving this problem, an international team of researchers used data from the Subaru Strategic Program (SSP) Hyper Suprime-Cam (HSC) to discover two entirely new satellite galaxies.
These results were published in Publications of the Astronomical Society of Japan on June 8, 2024 by a team of researchers from Japan, Taiwan and America.
We live in a galaxy called the Milky Way, which has other, smaller galaxies orbiting it, called satellite galaxies. Studying these satellite galaxies can help researchers unravel the mysteries surrounding dark matter and better understand how galaxies evolve over time.
The region observed by HSC-SSP (region bounded by red lines). Previously known satellite galaxies are marked with black squares, and newly discovered satellite galaxies are marked with white triangles and stars. Credit: NAOJ/Tohoku University
“How many satellite galaxies does the Milky Way have? This has been an important question for astronomers for decades,” notes Masahi Chiba, a professor at Tohoku University.
The research team recognized the possibility that there may be many undiscovered, small satellite galaxies (dwarf galaxies) that are far away and difficult to detect. The powerful capability of the Subaru Telescope, which sits atop an isolated mountain above the clouds in Hawaii, is well-suited to finding these galaxies. In fact, this research team previously found three new dwarf galaxies using the Subaru Telescope.
Now the team has discovered two more new dwarf galaxies (Virgo III and Sextans II). Thanks to this discovery, a total of nine satellite galaxies were found by different research teams. This is still far fewer than the 220 satellite galaxies predicted by standard dark matter theory.
Satellite galaxies around the Milky Way. The plane of the galactic disk is in the horizontal plane. The blue squares are the Large and Small Magellanic Clouds, and the red circles are other satellite galaxies. The fainter their absolute visual size, the smaller the point size. Credit: NAOJ/Tohoku University
However, the HSC-SSP footprint does not cover the entire Milky Way. If the distribution of these nine satellite galaxies throughout the Milky Way is similar to what was found in the track captured by HSC-SSP, the research team calculates that there may actually be closer to 500 satellite galaxies. We now face a “too many satellites problem” rather than a “missing satellites problem”.
More high-resolution imaging and analysis is needed to better characterize the true abundance of satellite galaxies. “The next step is to use a more powerful telescope to capture a wider view of the sky,” explains Chiba. “Next year, the Vera C. Rubin Observatory in Chile will be used to fulfill this purpose. I hope that many new satellite galaxies will be discovered.”
More information:
Daisuke Homma et al, Final results of the search for new Milky Way satellites in Subaru’s Hyper Suprime-Cam Strategic Program survey: Discovery of two more candidates, Publications of the Astronomical Society of Japan (2024). DOI: 10.1093/pasj/psae044
Provided by Tohoku University
Citation: Astronomers discover two new candidates for Milky Way satellite galaxy (2024, June 28) Retrieved June 29, 2024, from https://phys.org/news/2024-06-astronomers-milky-satellite-galaxy-candidates.html
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