A Disk and No Signatures of Tidal Distortion in the Galaxy “Lacking” Dark Matter NGC 1052-DF2

Abstract

Using ultra-deep imaging ( μ g = 30.4 mag arcsec −2 ; 3 σ , 10″ × 10″), we probed the surroundings of the first galaxy “lacking” dark matter (DM) KKS2000[04] (NGC 1052–DF2). Signs of tidal stripping in this galaxy would explain its claimed low content of DM. However, we find no evidence of tidal tails. In fact, the galaxy remains undisturbed down to a radial distance of 80″. This radial distance triples previous spatial explorations of the stellar distribution of this galaxy. In addition, the distribution of its globular clusters (GCs) is not extended in relation to the bulk of the galaxy (the radius containing half of the GCs is 21″). We also found that the surface brightness radial profiles of this galaxy in the g and r bands decline exponentially from 35″ to 80″. Together with a constant ellipticity and position angle in the outer parts of the galaxy, this strongly suggests the presence of a low-inclination disk. This is consistent with the evidence of rotation found for this object. This finding implies that the dynamical mass of this galaxy is a factor of 2 higher than previously reported, which brings the DM content of this galaxy in line with galaxies of similar stellar mass.