The "normal" elliptical galaxy NGC 3640 : a merger in progress ?

A photometric analysis reveals that NGC 3640 is a normal elliptical r^1/4^ galaxy with boxy isophotes, a minor-axis dust lane and patchy shell-like features. Long-slit spectroscopy shows that it is a fast rotator along its major axis, with (V/σ)^*^ ~1.5. No rotation is found along the minor axis. We show that NGC 3640 is a triaxial galaxy for the same reasons as, e.g., NGC 5128. We discuss the meaning of these characteristics and argue that NGC 3640 is a merger in progress that does not involve the compact companion NGC 3641, and at a more advanced stage of relaxation toward an elliptical than prototypes of merger products such as NGC 1316, 5018, 5128 or 7252. The galaxy involved in the merging probably is a gas-poor disk system.