Locations of Satellite Galaxies in the Two-Degree Field Galaxy Redshift Survey

TL;DR

This study analyzes satellite galaxy positions in the 2dF Galaxy Redshift Survey, revealing anisotropic distributions aligned with host galaxy axes, with star formation activity influencing satellite location patterns.

Contribution

It provides the first detailed analysis of satellite galaxy anisotropy using the 2dF survey, highlighting the influence of star formation on satellite distribution.

Findings

Satellites are preferentially located near host major axes with high statistical significance.

High-velocity satellites show similar anisotropic distributions as low-velocity satellites.

Passive star-forming satellites exhibit anisotropic distributions, unlike star-forming satellites.

Abstract

We compute the locations of satellite galaxies in the Two-Degree Field Galaxy Redshift Survey using two sets of selection criteria and three sources of photometric data. Using the SuperCOSMOS r_F photometry, we find that the satellites are located preferentially near the major axes of their hosts, and the anisotropy is detected at a highly-significant level (confidence levels of 99.6% to 99.9%). The locations of satellites that have high velocities relative to their hosts are statistically indistinguishable from the locations of satellites that have low velocities relative to their hosts. Additionally, satellites with passive star formation are distributed anisotropically about their hosts (99% confidence level), while the locations of star-forming satellites are consistent with an isotropic distribution. These two distributions are, however, statistically indistinguishable. Therefore it is not correct to interpret this as evidence that the locations of the star-forming satellites are intrinsically different from those of the passive satellites.