Galactic spins carry fingerprints of the primordial universe
The origin of spin in spiral and elliptical galaxies has posed a long-standing puzzle for astronomers. One idea, known as tidal torque theory, proposes that galaxies' spins are an imprinted record of the early universe, imparted by gravity long before galaxies first formed and still detectable in galaxies today.
A new study, published in Nature Astronomy, has put to the test the notion that the spins of spiral and elliptical galaxies carry the fingerprints of the primordial universe. This idea, known as tidal torque theory, posits that the spin of galaxies is an imprinted record of the early universe, shaped by gravity as galaxies formed. Led by Ming-Jie Sheng from Xiamen University, the research team has subjected this theory to its most rigorous examination yet, with promising results.
The angular momentum of a galaxy's spin is a crucial factor determining its size, shape, and internal dynamics. The theory suggests that this spin can be traced back to the most ancient structures in the cosmos, where gravitational forces from uneven clumps of gas and dark matter set the stage for the galaxy's rotation. However, confirming this idea has been a challenge due to the complexities involved.
To address this, the researchers utilized data from the ELUCID project, a tool that reconstructs the early universe's matter distribution based on today's galaxy positions. By tracing the galaxy spin patterns back to the primordial tidal forces responsible for their creation, they compared these predictions with actual spin measurements obtained through an instrument that measures the motion of gas and stars within individual galaxies from the nearby universe.
The strongest correlation between predicted and observed galaxy spins was observed in the gas within large, massive elliptical galaxies. This correlation was so strong that it ruled out the possibility of it being a coincidence, providing the clearest evidence yet that today's galaxies do indeed retain an imprint from the universe's infancy.
While the rotation of most galaxies is still disrupted by mergers and ongoing growth, the study confirms that the spin of galaxies is not entirely random but is indeed connected to the early universe's tidal forces.
Beyond confirming tidal torque theory, this research could also offer a novel way to measure certain aspects of the universe that are otherwise difficult to ascertain, including elusive components like neutrinos. The implications of this discovery are far-reaching, potentially providing insights into the subtle and fundamental elements that make up our universe.
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