Friends-of-friends galaxy group finder with membership refinement. Application to the local Universe
E. Tempel, R. Kipper, A. Tamm, M. Gramann, M. Einasto, T. Sepp, T., Tuvikene

TL;DR
This paper enhances the friends-of-friends galaxy group finding algorithm with membership refinement to better detect subgroups and suppress observational effects, resulting in a comprehensive catalog of galaxy groups in the local Universe.
Contribution
We developed a refined FoF algorithm with subgroup detection and applied it to local galaxy data, improving group identification accuracy and mass estimation.
Findings
Detected 6282 galaxy groups within 430 Mpc radius.
Refined group memberships by using virial radius and escape velocity.
Split large groups into smaller subgroups, revealing substructure.
Abstract
Context. Groups form the most abundant class of galaxy systems. They act as the principal drivers of galaxy evolution and can be used as tracers of the large-scale structure and the underlying cosmology. However, the detection of galaxy groups from galaxy redshift survey data is hampered by several observational limitations. Aims. We improve the widely used friends-of-friends (FoF) group finding algorithm with membership refinement procedures and apply the method to a combined dataset of galaxies in the local Universe. A major aim of the refinement is to detect subgroups within the FoF groups, enabling a more reliable suppression of the fingers-of-God effect. Methods. The FoF algorithm is often suspected of leaving subsystems of groups and clusters undetected. We used a galaxy sample built of the 2MRS, CF2, and 2M++ survey data comprising nearly 80000 galaxies within the local…
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