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The Origin of Angular Momentum in Cosmological Structures

Ebrahimian, Ehsan | 2022

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 55467 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Abolhassani, Ali Akbar
  7. Abstract:
  8. Explaining the angular momentum of the cosmological structures is an essential part of the structure formation theory, and it is not fully understood yet. The Tidal Torque Theory (TTT) is the standard explanation of the initial angular momentum of the halos based on the gravitational instability picture. It predicts the angular momentum growth with linear approximation and has been confirmed for linear stages of proto-halos, but the final halo is a highly non-linear object. Nonlinear effects are hard to model, however, we propose a new mechanism for the nonlinear evolution of the halos. We suggest that when two halos pass by each other, their angular momentum changes with a similar mechanism to the tidal locking, so we dubbed it Tidal Locking Theory (TLT). We argue that the TTT is responsible for the initial angular momentum of the halos, and TLT is responsible for the spin evolution of the dark matter halos. We model this effect and examine our scenario with dark matter simulations. By using the TNG50-1-Dark simulation we show that the initial direction of the dark matter halos, follows the TTT prediction, but in lower redshifts, the spin aligns with the TLT prediction. By using the Illustris-1-Dark, we show that the evolution of the spin of dark matter halos agrees with the TLT prediction. We think that the Tidal locking Theory can give a viable explanation for the spin-LSS alignment of the dark matter halos.
  9. Keywords:
  10. Angular Momentum ; Large Scale Structure ; Dark Matter Halo ; Spin-Large Scale Structure (LSS)Alignment ; Cosmological Structure Formation

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