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Simulations Suggest Milky Way Formed From Thousands of Galaxies
Confirmed
In Short: Researchers at the University of Washington have developed simulations suggesting the Milky Way could have formed from the merger of thousands of smaller galaxies, rather than just a few.
These simulations, which omitted small dark matter clumps called subhalos, showed that the structure of galaxies themselves could create many of the same stellar stream distortions previously attributed to dark matter.
The team modeled roughly 15,000 stellar streams across four Milky Way-sized galaxies, finding that the distortions arose from the galaxies' own structure.
The findings challenge previous assumptions about the role of dark matter in shaping the Milky Way.
By taking about 40 observations, they built a catalog of nearly 2.5 million detections, split roughly evenly between the two galaxies.
The James Webb Space Telescope (JWST) is also contributing to our understanding of galaxy formation, with one of its main objectives being to understand how galaxies came to host supermassive black holes.
What this adds
This research adds to the understanding of how the Milky Way and other galaxies may have formed, challenging previous theories about the role of dark matter.
The simulations suggest that the Milky Way's formation involved a complex interplay of galaxy mergers and internal structures, rather than just the influence of dark matter.
Background
Researchers at the University of Washington have developed simulations suggesting the Milky Way could have formed from the merger of thousands of smaller galaxies, rather than just a few.
What's confirmed
- These simulations, which omitted small dark matter clumps called subhalos, showed that the structure of galaxies themselves could create many of the same stellar stream distortions previously attributed to dark matter.
- The team modeled roughly 15,000 stellar streams across four Milky Way-sized galaxies, finding that the distortions arose from the galaxies' own structure.
- The findings challenge previous assumptions about the role of dark matter in shaping the Milky Way.
- By taking about 40 observations, they built a catalog of nearly 2.5 million detections, split roughly evenly between the two galaxies.
- The James Webb Space Telescope (JWST) is also contributing to our understanding of galaxy formation, with one of its main objectives being to understand how galaxies came to host supermassive black holes.
What's still developing
- That's unusual enough – but the researchers spotted the behavior twice, four days and some 225 kilometers (140 miles) apart, suggesting this wasn't simply a chance encounter, but that the amphipods may be deliberately seeking out the sea spiders.
- Thousands of meters below the Southeast Pacific Ocean, scientists have documented just such a partnership.
- There's widespread agreement that large galaxies in today's Universe host supermassive black holes (SMBH).
- A*, the Milky Way's SMBH, has more than four million solar masses.
- "The tight relation between black hole mass and galaxy properties, such as stellar velocity dispersion, bulge mass, and stellar mass observed in the local universe implies that SMBHs influence star formation in galaxies through feedback from active galactic nucleus (AGN) activity," they write.
- Astronomers using ESO’s Visible and Infrared Survey Telescope for Astronomy (VISTA) have observed the densest, most crowded regions at the centers of the Large and Small Magellanic Clouds, our Milky Way Galaxy’s closest dwarf companions, offering an unprecedented look at areas that have long resisted detailed study.
- “The central regions of galaxies are hard to study: dust partially blocks our view, and stars are so densely packed that it’s difficult to tell them apart,” said Professor Maria-Rosa Cioni from the Leibniz Institute for Astrophysics and her colleagues.
- “With these data, astronomers could then measure the subtle motion of stars in the cores, which is key to pinpoint the exact location of the centers of these galaxies,” the authors said.
- Roughly two-thirds of these sources are likely genuine stars, while the remainder may be blended stars or background galaxies.
- Unlike many other spiral galaxies, like this one recently photographed by Hubble, NGC 4698’s delicate spiral arms are only prominent in the outer reaches of the disk; spiral arms often wind down to the very center of a galaxy, but NGC 4698’s spiral arms appear to shy away from its glowing center.
- It’s one of over a thousand galaxies in the Virgo Cluster, the nearest large cluster of galaxies bound together by gravity.
- As a spiral galaxy similar to our own Milky Way galaxy, NGC 4698 has spiral arms that curl around within a thin disk of stars, gas, and dust.