A Tale of NGC 3785: The Formation of an Ultra-Diffuse Galaxy at the end of the Longest Tidal Tail

TL;DR

This paper reports the discovery of a faint, extended tidal tail associated with galaxy NGC 3785, providing observational evidence for ultra-diffuse galaxy formation at the tail's end through analysis of low surface brightness structures and star-forming regions.

Contribution

It presents the first observational evidence linking a long tidal tail to the formation of an ultra-diffuse galaxy at its end, using deep optical imaging and photometric analysis.

Findings

Detected a 390 kpc long faint tidal tail in NGC 3785

Identified 84 star-forming clumps along the tail

Proposed tail formation from galaxy interaction leading to ultra-diffuse galaxy

Abstract

We present the discovery of an extended and faint tail observed in the isolated environment associated with galaxy NGC 3785. This study additionally provides observational evidence supporting the formation of ultra-diffuse galaxies at the end of the tail. We utilized the Gnuastro software to detect and analyse the low surface brightness structures in the optical $g$, and $r$ bands using data from the Dark Energy Camera Legacy Survey. We created a detection map to identify the faint tail, and measured its length using cubic spline fitting. Additionally, we found 84 star-forming clumps along the tail and performed photometric analysis on the tail portion after applying a significance threshold on the signal-to-noise ratio. We have measured the projected length of the tail, which is $\sim$390 kpc. We propose that this tail arises from the interaction of the NGC 3785 with a gas-rich galaxy, which ends up as ultra-diffuse galaxy at the end of the tail.