The creation of a massive UCD by tidal threshing from NGC 936

TL;DR

This study investigates a compact nucleus within a dwarf galaxy undergoing tidal disruption by a nearby giant galaxy, revealing that such processes can produce bright UCDs with specific stellar properties.

Contribution

The paper presents evidence that tidal threshing of dwarf galaxies near massive galaxies can create bright UCDs with distinct characteristics.

Findings

NGC 936_UCD shares properties with typical UCDs but is larger and brighter.

The disrupted dwarf progenitor has a luminosity typical of bright dwarf ellipticals.

Tidal threshing is a plausible formation mechanism for bright UCDs near giant galaxies.

Abstract

We study a compact nucleus embedded in an early-type dwarf galaxy, MATLAS-167, which is in the process of disruption by the tidal force of the neighboring giant S0 galaxy, NGC 936, in a group environment. Using the imaging data of the MATLAS survey, we analyze the stellar tidal tail of MATLAS-167 and its central compact nucleus, designated as NGC 936_UCD. We find that NGC 936_UCD has a luminosity of M$_{g}$ = $-$11.43$\pm$0.01 mag and a size of 66.5$\pm$17 pc, sharing the global properties of Ultra Compact Dwarf galaxies (UCDs) but significantly larger and brighter compared to the typical UCD populations observed in the Virgo cluster. By integrating the total luminosity of both the tidal stream and MATLAS-167, we estimate that the disrupted dwarf progenitor possesses a luminosity of M$_{g}$ = $-$15.92$\pm$0.06 mag, a typical bright dE luminosity. With the help of the optical spectrum observed by the SDSS survey, we derive the simple stellar population properties of NGC 936_UCD: a light-weighted age of 5.6$\pm$0.7 Gyr and metallicity of [Z/H] = $-$0.83$\pm$0.3 dex. Our findings suggest that tidal threshing is a possible formation mechanism of bright UCD populations in close proximity to giant galaxies.