On the origin of the spin–orbit alignment in galaxy pairs

Abstract: 

Recent studies suggest a coherence between the spin vector of a galaxy and the orbital motion of its closest neighbor, yet its origin is still a matter of debate. We analyze the spin–orbit orientation in galaxy pairs using the IllustrisTNG cosmological simulation. We find that the spin–orbit orientations are preferentially prograde, and the alignment is much stronger for closer and more gas-rich pairs residing in lower-density environments. Traced back in time, pairs selected at z = 0 were initially random in terms of the orientation at the time of infall, and later on the alignment gets stronger over time. The strength of the alignment correlates with the integrated tidal force from the neighbor. Our results favor the scenario in which the spin–orbit alignment in galaxy pairs is originated from the perturbation of an interacting neighbor, rather than from the tidal torque by the primordial large‐scale structure.

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Presentation Type: 
Poster