Living with Neighbors. IV. Dissecting the Spin-Orbit Alignment of Dark Matter Halos: Interacting Neighbors and the Local Large-scale Structure

Sung Ho An, Juhan Kim, Jun Sung Moon, Suk Jin Yoon

Research output: Contribution to journalArticlepeer-review

Abstract

Spin-orbit alignment (SOA; i.e., the vector alignment between the halo spin and the orbital angular momentum of neighboring halos) provides an important clue to how galactic angular momenta develop. For this study, we extract virial-radius-wise contact halo pairs with mass ratios between 1/10 and 10 from a set of cosmological N-body simulations. In the spin-orbit angle distribution, we find a significant SOA in that 52.7% ± 0.2% of neighbors are on the prograde orbit. The SOA of our sample is mainly driven by low-mass target halos (<1011.5 h -1 M o˙) with close merging neighbors, corroborating the notion that tidal interaction is one of the physical origins of SOA. We also examine the correlation of SOA with the adjacent filament and find that halos closer to the filament show stronger SOA. Most interestingly, we discover for the first time that halos with the spin parallel to the filament experience most frequently prograde polar-interaction (i.e., fairly perpendicular but still prograde interaction; spin-orbit angle ∼70°). This instantly invokes the spin-flip event and the prograde-polar interaction will soon flip the spin of the halo to align it with the neighbor's orbital angular momentum. We propose that SOA originates from the local cosmic flow along the anisotropic large-scale structure, especially that along the filament, and grows further by interactions with neighbors.

Original languageEnglish
Article number86
JournalAstrophysical Journal
Volume914
Issue number2
DOIs
Publication statusPublished - 2021 Jun 20

Bibliographical note

Publisher Copyright:
© 2021. The American Astronomical Society. All rights reserved.

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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