SDSS J124155.33+114003.7 – a missing link between compact elliptical and ultracompact dwarf galaxies

Abstract

Abstract We report the discovery of a compact object (Re= 32 pc, MB=−12.34 mag) at a projected distance of 9 kpc from Messier 59, a giant elliptical in the Virgo cluster. Using HST imaging and SDSS spectroscopy, both available in the Virtual Observatory, we find that this object has a blue core containing one-quarter of the light, and a redder n= 1 Sérsic envelope, as well as luminosity-weighted age of 9.3 ± 1.4 Gyr, a metallicity of −0.03 ± 0.04 dex and a velocity dispersion of 48 ± 5 km s−1. While ultracompact dwarf galaxies (UCDs) in the face-on view of the Fundamental Plane are found to form a sequence connecting the highest-luminosity globular clusters with the lowest-luminosity dwarf ellipticals, the compact object near M59 lies in between this UCD sequence and the positions of compact ellipticals. Its stellar age, metallicity, and effective surface brightness are similar to low-luminosity ellipticals and lenticulars, suggesting that SDSS J124155.33+114003.7 is a result of the tidal stripping of such an object.