VEGAS: A VST Early-type GAlaxy Survey. IV. NGC 1533, IC 2038, and IC 2039: An Interacting Triplet in the Dorado Group

Abstract

This paper focuses on NGC 1533 and the pair IC 2038 and IC 2039 in Dorado a nearby, clumpy, still un-virialized group. We obtained their surface photometry from deep OmegaCAM@ESO-VST images in g and r bands. For NGC 1533, we map the surface brightness down to μ <SUB> g </SUB> ≃ 30.11 mag arcsec<SUP>-2</SUP> and μ <SUB> r </SUB> ≃ 28.87 mag arcsec<SUP>-2</SUP> and out to about 4 R <SUB> e </SUB>. At such faint levels, the structure of NGC 1533 appears amazingly disturbed with clear structural asymmetry between inner and outer isophotes in the northeast direction. We detect new spiral arm-like tails in the outskirts, which might likely be the signature of a past interaction/merging event. Similarly, IC 2038 and IC 2039 show tails and distortions indicative of their ongoing interaction. Taking advantage of deep images, we are able to detect the optical counterpart to the H I gas. The analysis of the new deep data suggests that NGC 1533 had a complex history made of several interactions with low-mass satellites that generated the star-forming spiral-like structure in the inner regions and are shaping the stellar envelope. In addition, the VST observations also show that the two less luminous galaxies, IC 2038 and IC 2039, are probably interacting each other and IC 2038 could have also interacted with NGC 1533 in the past, which stripped away gas and stars from its outskirts. The new picture emerging from this study is that of an interacting triplet, where the brightest galaxy, NGC 1533, has ongoing mass assembly in the outskirts.