Satellite Alignment: I. Distribution of Substructures and Their Dependence On Assembly History From N-Body Simulations

Abstract

Observations have shown that the spatial distribution of satellite galaxies is not random, but aligned with the major axes of central galaxies. This alignment is dependent on galaxy properties, such that red satellites are more strongly aligned than blue satellites. Theoretical work done to interpret this phenomena has found that it is due to the non-spherical nature of dark matter halos. However, most studies over-predict the alignment signal under the assumption that the central galaxy shape follows the shape of the host halo. It is also not clear whether the color dependence of alignment is due to an assembly bias or an evolution effect. In this paper we study these problems using a cosmological N-body simulation. Subhalos are used to trace the positions of satellite galaxies. It is found that the shape of dark matter halos are mis-aligned at different radii. If the central galaxy shares the same shape as the inner host halo, then the alignment effect is weaker and agrees with observational data. However, it predicts almost no dependence of alignment on the color of satellite galaxies, though the late accreted subhalos show stronger alignment with the outer layer of the host halo than their early accreted counterparts. We find that this is due to the limitation of pure N-body simulations that satellites galaxies without associated subhalos ('orphan galaxies') are not resolved. These orphan (mostly red) satellites often reside in the inner region of host halos and should follow the shape of the host halo in the inner region.

12 pages, 11 figures, Published on ApJ

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Cited by in corpus (12)

• The alignment of satellite galaxies and cosmic filaments: observations and simulations
• Intrinsic alignments of galaxies in the MassiveBlack-II simulation: analysis of two-point statistics
• The build up of the correlation between halo spin and the large scale structure
• Alignments between galaxies, satellite systems and haloes
• Evolution of galactic planes of satellites in the EAGLE simulation
• The Distribution of Satellites Around Central Galaxies in a Cosmological Hydrodynamical Simulation
• Alignments of the Galaxies in and around the Virgo Cluster with the Local Velocity Shear
• The tilting rate of the Milky Way's disc
• Detection of the velocity shear effect on the spatial distributions of the galactic satellites in isolated systems
• Galaxy clusters as intrinsic alignment tracers: present and future
• Living with Neighbors. IV. Dissecting the Spin$-$Orbit Alignment of Dark Matter Halos: Interacting Neighbors and the Local Large-scale Structure
• Halo cluster shapes: Insights from simulated galaxies and ICL with prospects for weak lensing applications