The Evil Eye galaxy stands out with its ominous appearance and peculiar characteristics. However, its eerie nature goes beyond its visual aesthetics. M64's outer disk, rich in hydrogen, exhibits a unique feature-the opposite orbit compared to the inner disk of stars. This suggests that these two components originated from different sources, further adding to the galaxy's enigmatic nature.
In the research, titled "Origins of the Evil Eye: M64's Stellar Halo Reveals the Recent Accretion of an SMC-mass Satellite" available in arXiv and has been accepted into The Astrophysical Journal Letters, astronomers shed light on the origins of M64's outer disk. It has been discovered that the hydrogen gas in this region originated from a smaller dwarf galaxy, which was rich in gas.
Galaxy Mergers Important for Galaxy Growth
Galaxy mergers play a significant role in the growth and evolution of galaxies. According to Science Alert, these events not only increase a galaxy's mass but also introduce new material and gravitational interactions that promote star formation, ensuring the continuous formation of new generations of stars.
Throughout its 13.6 billion-year history, the Milky Way has undergone multiple mergers with other galaxies. Additionally, in the vast expanse of the universe, we can observe other galaxies in various stages of the merging process.
As the galactic cannibalism is a common phenomenon, it was reasonable to assume that the peculiar gas found on the outskirts of M64 was the result of such an event.
However, previous studies yielded few indications of a recent interaction between galaxies, leading to suggestions that the hydrogen disk might have originated from the surrounding space or from a brief encounter with another galaxy called Coma P. Nevertheless, there was limited evidence supporting either scenario.
To investigate further, astronomers, led by Smercina and his colleagues, utilized the Subaru telescope's Hyper Suprime-Cam to examine the region around M64, located approximately 1.4 million light-years away.
Their observations revealed clear signs of a galactic merger. They identified a galactic halo, a diffuse sphere composed of dark matter, gas, and stars, enveloping spiral galaxies. This halo is believed to form and grown through galaxy mergers, providing compelling evidence for the occurrence of such an event in M64's history.
New Evidence for the Origins of M64 Galaxy's Outer Disk
In their quest to unravel the mysteries of M64, Phys.org reported that the team employed data from the Subaru telescope's Hyper Suprime-Cam. They examined the surrounding areas and made an intriguing discovery-a galactic halo, a telltale sign of galaxy mergers. This finding indicated that M64 had undergone a merger event in the past.
Further investigation revealed the presence of a dense cluster of stars called a shell. These formations also arise during galaxy mergers, where gravitational interactions push stars together.
To validate their observations, the team turned to data from the Hubble Space Telescope. Analyzing this data allowed them to estimate the composition and mass of the absorbed galaxy they suspected was involved in the merger.
The results indicated striking similarities between the absorbed galaxy and the Small Magellanic Cloud, a nearby small galaxy that is gradually being cannibalized by the Milky Way. The density of the absorbed galaxy was approximately 500 million times the mass of our Sun, similar to the mass of the hydrogen disk forming the outer region of M64. The researchers concluded that their collective findings strongly support the hypothesis that M64's outer hydrogen disk originated from the cannibalization of a dwarf galaxy.
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