AGC 226178 and NGVS 3543: Two deceptive dwarfs towards Virgo

TL;DR

This study clarifies the nature of two faint systems near Virgo, revealing one as a foreground object and the other as a young, gas-stripped dwarf galaxy likely formed from interactions, highlighting ongoing galaxy formation processes.

Contribution

The paper demonstrates that NGVS 3543 is a foreground object and confirms AGC 226178 as a young, gas-stripped dwarf galaxy formed from nearby gas, providing new insights into galaxy interactions in Virgo.

Findings

NGVS 3543 is a foreground object at ~10 Mpc.

AGC 226178 is a young (10-100 Myr) galaxy in Virgo.

AGC 226178 likely formed from gas stripped from VCC 2034.

Abstract

The two sources AGC 226178 and NGVS 3543, an extremely faint, clumpy, blue stellar system and a low surface brightness dwarf spheroidal, are adjacent systems in the direction of the Virgo cluster. Both have been studied in detail previously, with it being suggested that they are unrelated normal dwarf galaxies or that NGVS 3543 recently lost its gas through ram pressure stripping, and that AGC 226178 formed from this stripped gas. However, with HST ACS imaging we demonstrate that the stellar population of NGVS 3543 is inconsistent with being at the distance of the Virgo cluster, and that it is likely a foreground object at approximately 10 Mpc. Whereas the stellar population of AGC 226178 is consistent with it being a very young (10-100 Myr) object in the Virgo cluster. Through a re-analysis of the original ALFALFA HI detection we show that AGC 226178 likely formed from gas stripped from the nearby dwarf galaxy VCC 2034, a hypothesis strengthened by the high metallicity measured with MUSE VLT observations. However, it is unclear whether ram pressure or a tidal interaction is responsible for stripping the gas. AGC 226178 is one of at least five similar objects now known towards Virgo. These objects are all young and unlikely to remain visible for over ~500 Myr, suggesting that they are continually produced in the cluster.