Multicolor Photometry of the Nearby Galaxy Cluster A119

TL;DR

This study uses multicolor optical photometry to analyze the structure, composition, and star formation history of the nearby galaxy cluster Abell 119, revealing its complex substructure and environmental effects on galaxy evolution.

Contribution

It provides a detailed analysis of A119's substructures and star formation properties using multicolor photometry and photometric redshifts, which is a novel comprehensive approach for this cluster.

Findings

A119 has at least three substructures within 1 Mpc.

The central region shows signs of line-of-sight merging.

Faint galaxies in low-density areas have longer star formation timescales.

Abstract

This paper presents multicolor optical photometry of the nearby galaxy cluster Abell 119 (z = 0:0442) with the Beijing-Arizona-Taiwan-Connecticut (BATC) system of 15 intermediate bands. Within the BATC viewing field of 58'* 58', there are 368 galaxies with known spectroscopic redshifts, including 238 member galaxies (called sample I). Based on the spectral energy distributions (SEDs) of 1376 galaxies brighter than iBATC = 19:5, photometric redshift technique and the color-magnitude relation of earlytype galaxies are applied to select faint member galaxies. As a result, 117 faint galaxies were selected as new member galaxies. Combined with sample I, an enlarged sample (called sample II) of 355 member galaxies is obtained. Spatial distribution and localized velocity structure for two samples demonstrate that A119 is a dynamically complex cluster with at least three prominent substructures in the central region within 1 Mpc. A large velocity dispersion for the central clump indicates a merging along the line of sight. No significant evidences for morphology and luminosity segregations are found in both samples. With the evolutionary synthesis model PEGASE, environmental effect on the star formation properties is confirmed. Faint galaxies in low-density region tend to have longer time scales of star formation, smaller mean stellar ages, and lower metallicities of interstellar medium, which is in agreement with the context of hierarchical cosmological scenario.