Optical Structure and Evolution of the Arp 104 Interacting Galaxy System

TL;DR

This study investigates the optical structure and evolution of the interacting galaxy pair Arp 104, revealing complex stellar populations, gas distributions, and interaction features that suggest a hierarchical merging process leading to galaxy transformation.

Contribution

It provides detailed optical imaging and analysis of Arp 104, highlighting the role of multiple interactions in galaxy evolution and the formation of an early-type galaxy.

Findings

NGC 5216 is on the red sequence.

NGC 5218 shows intense central star formation and intermediate color.

The stellar bridge is gas-poor with uniform optical surface brightness.

Abstract

Arp 104 is a pair of luminous interacting galaxies consisting of NGC 5216, an elliptical, and NGC 5218, a disturbed disk galaxy and joined by a stellar bridge. We obtained optical imaging to support photometric and color studies of the system. NGC 5216 lies on the red sequence, while the unusual distribution of stellar population properties in combination with intense central star formation in a dusty region result in NGC 5218 being a nearby example of an intermediate color (green valley) system. The stellar bridge has remarkably uniform optical surface brightness, with colors consistent with its stars coming from the outskirts of NGC 5218, but is relatively gas-poor while the northern tidal tail is rich in HI. While both galaxies contain shells, the shell structures in NGC 5218 are pronounced, and some appear to be associated with counter-rotating gas. This combination of features suggests that Arp 104 could be the product of distinct multiple interactions in a small galaxy group, possibly resulting from a hierarchical merging process, and likely leading to the birth of a relatively massive and isolated early-type galaxy.