Testing the Bullet Dwarf Collision Scenario in the NGC 1052 Group Through Morphologies and Stellar Populations

TL;DR

This study investigates the bullet dwarf collision hypothesis for the formation of a dwarf galaxy trail in the NGC 1052 group by analyzing morphologies and stellar populations using Hubble data.

Contribution

It provides observational evidence supporting the bullet dwarf collision scenario through detailed morphological and stellar population analysis.

Findings

Trail dwarfs have older ages and higher metallicities.

No significant morphological differences between trail and other dwarfs.

Major axes align parallel with the trail.

Abstract

NGC 1052-DF2 and -DF4 are two ultra-diffuse galaxies that have been reported as deficient in dark matter and associated with the same galaxy group. Recent findings suggest that DF2 and DF4 are part of a large linear substructure of dwarf galaxies that could have been formed from a high-velocity head-on encounter of two gas-rich galaxies, known as a bullet dwarf collision. Based on new observations from the Hubble Space Telescope, combined with existing imaging from the u band to mid-infrared, we test the bullet dwarf scenario by studying the morphologies and stellar populations of the trail dwarfs. We find no significant morphological differences between the trail dwarfs and other dwarfs in the group, while for both populations, their photometric major axes unexpectedly align parallel with the trail. We find that the trail dwarfs have significantly older ages and higher metallicities than the comparison sample, supporting the distinctiveness of the trail. These observations provide key constraints for any formation model, and we argue that they are currently best explained by the bullet dwarf collision scenario, with additional strong tests anticipated with future observations.