Galaxy Luminosity Function of Dynamically Young Abell 119 Cluster: Probing the Cluster Assembly

TL;DR

This study analyzes the galaxy luminosity function of Abell 119, revealing a bimodal shape influenced by cluster environment and substructure, supporting hierarchical cluster formation.

Contribution

First detailed LF measurement of Abell 119 down to faint magnitudes, linking LF features to cluster assembly and substructure.

Findings

LF shows a bimodal shape with a dip at M_r~ -17.8 mag.

LF varies with cluster-centric distance and local density.

Overdense regions retain a two-component LF with a dip, indicating galaxy group remnants.

Abstract

We present the galaxy luminosity function (LF) of the Abell 119 cluster down to $M_r\sim-14$ mag based on deep images in the $u$-, $g$-, and $r$-bands taken by using MOSAIC II CCD mounted on the Blanco 4m telescope at the CTIO. The cluster membership was accurately determined based on the radial velocity information as well as on the color-magnitude relation for bright galaxies and the scaling relation for faint galaxies. The overall LF exhibits a bimodal behavior with a distinct dip at $r\sim18.5$ mag ($M_r\sim-17.8$ mag), which is more appropriately described by a two-component function. The shape of the LF strongly depends on the cluster-centric distance and on the local galaxy density. The LF of galaxies in the outer, low-density region exhibits a steeper slope and more prominent dip compared with that of counterparts in the inner, high-density region. We found evidence for a substructure in the projected galaxy distribution in which several overdense regions in the Abell 119 cluster appear to be closely associated with the surrounding, possible filamentary structure. The combined LF of the overdense regions exhibits a two-component function with a distinct dip, while the LF of the central region is well described by a single Schechter function. We suggest that, in the context of the hierarchical cluster formation scenario, the observed overdense regions are the relics of galaxy groups, retaining their two-component LFs with a dip, which acquired their shapes through galaxy merging process in group environments, before they fall into a cluster.