Star Formation in the Elliptical (?) Galaxy NGC 5173

Using the MaNGaL tunable-filter photometer at the 2.5-m telescope of the Caucasian Mountain Observatory of the Sternberg Astronomical Institute of Lomonosov Moscow State University, we studied star formation in an early-type gas-rich galaxy, which was until now considered to be elliptical, NGC 5173. The gas has probably been accreted in the recent past by the galaxy from a direction inclined to its disk. Star formation that we observe now has led in the past 400 Myr to the formation of compact massive clusters with shock excitation of gas around them-a star formation behavior corresponding to what is usually observed in the interacting Antennae-like galaxies. In combination with the almost solar metallicity of the gas, this allows us to conclude that NGC 5173 has assimilate a very gas-rich companion with a mass of at least 10-20% of its own stellar mass.