Clues on Arp 142: The Spiral-Elliptical merger
  Nearby merging pairs are unique laboratories in which one can study the
gravitational effects on the individual interacting components. In this
manuscript, we report the characterization of selected HII regions along the
peculiar galaxy NGC 2936, member of the galaxy pair Arp 142, an E+S
interaction, known as "The Penguin". Using Gemini South spectroscopy we have
derived a high enhancement of the global star formation rate SFR=35.9 Msun/yr
probably stimulated by the interaction. Star-forming regions on this galaxy
display oxygen abundances that are consistent with solar metallicities. The
current data set does not allow us to conclude any clear scenario for NGC 2936.
Diagnostic diagrams suggest that the central region of NGC 2936 is ionized by
AGN activity and the eastern tidal plume in NGC 2936 is experiencing a burst of
star formation, which may be triggered by the gas compression due to the
interaction event with its elliptical companion galaxy: NGC 2937. The
ionization mechanism of these sources is consistent with shock models of
low-velocities of 200-300 km/s The isophotal analysis shows tidal features on
NGC 2937: at inner radii non-concentric (or off-centering) isophotes, and at
large radii, a faint excess of the surface brightness profile with respect to
de Vaucouleurs law. By comparing the radial velocity profiles and morphological
characteristics of Arp 142 with a library of numerical simulations, we conclude
that the current stage of the system would be about 50 +-25 Myr after the first
pericenter passage.
