A recent merger in the Fornax dwarf spheroidal galaxy

Abstract

This contribution describes a recent photometric survey of the Fornax dwarf spheroidal galaxy. CCD photometry in two colours (V and I) was obtained for a 10 degree2 region centred on Fornax. By selecting stars sharing the colour-magnitude space of this system's RGB, we were able to remove the majority of field stars, and thereby probe the structure of Fornax at a previously unattained level. The data indicate that this dwarf galaxy contains two shells, both aligned with the Fornax major axis. Also, two 'lobed' structures sharing the alignment of these shells were discovered beyond the nominal tidal radius. These structures appear to be the remnant of a companion dwarf galaxy which merged with Fornax approximately 2 Gyr ago.