A galaxy formed by collapse typically exhibits several distinctive characteristics that reflect its formation process. One of the primary marks is a bulge or core structure at its center, which is often surrounded by a disk of stars, gas, and dust. This structure indicates that the galaxy has undergone significant gravitational collapse, leading to the concentration of mass in the core.
In addition to the bulge, other marks of a collapse-formed galaxy include:
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Elliptical Shape: Many galaxies formed by collapse have an elliptical or spheroidal appearance, characterized by a more uniform distribution of stars, without the well-defined spiral structure seen in spiral galaxies.
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Older Stellar Population: Collapse-formed galaxies often contain older stars, as the initial burst of star formation occurs early in the galaxy's life. They may have a lower rate of ongoing star formation compared to other types.
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Lack of Gas: These galaxies may have depleted gas supplies due to the intense star formation at their formation, leading to less ongoing star formation activity.
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Stellar Dynamics: The stars in a collapsing galaxy can show different kinematic properties, such as less ordered motion compared to more dynamically relaxed systems like spiral galaxies.
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Merger and Interaction Traces: Sometimes, a galaxy can be formed through the merger of smaller galaxies or gas clouds, resulting in features like tidal tails or other irregularities.
These characteristics help astronomers understand the formation and evolution of galaxies in the universe.