The peculiar galaxy Mkn 298 revisited with integral field spectroscopy

Spectroscopic and imaging data of the peculiar galaxy Mkn 298 are presented. Narrow-band Hα and broad-band R images are used to study the star formation rate in the galaxy and its morphology, which is typical of a merging system. Long-slit and integral field spectra are used to assess the kinematics of gas and stars, and the nature of the ionizing source at different distances from the nucleus. In particular, the nucleus of Mkn 298 is characterized by peculiar line ratios: [N II]λ6583/Hα is typical of H II-like regions, while [O I]λ6300/Hα could indicate the presence of an active galactic nucleus. We show that models where a shock component is added to photoionization from a starburst allow us to reproduce the observed line ratios. Mkn 298 is thus most likely a star-forming galaxy, rather than a galaxy hosting an active nucleus. Based on data obtained at the 2.2m and NTT telescopes of ESO-la Silla (Chile), at the 2.2m telescope of DSAZ-Calar Alto (Spain), and at the 6m telescope of SAO (Russia).