Tidal interaction, star formation and chemical evolution in blue compact
  dwarf galaxy Mrk 22
  The optical spectroscopic and radio interferometric HI 21 cm-line
observations of the blue compact dwarf galaxy Mrk 22 are presented. The
Wolf-Rayet (WR) emission line features corresponding to high ionization lines
of HeII $\lambda$4686 and CIV $\lambda$5808 from young massive stars are
detected. The ages of two prominent star forming regions in the galaxy are
estimated as $\sim$10 Myr and $\sim$ 4 Myr. The galaxy has non-thermal radio
deficiency, which also indicates a young star-burst and lack of supernovae
events from the current star formation activities, consistent with the
detection of WR emission lines features. A significant N/O enrichment is seen
in the fainter star forming region. The gas-phase metallicities [12 + log(O/H)]
for the bright and faint regions are estimated as 7.98$\pm$0.07 and
7.46$\pm$0.09 respectively. The galaxy has a large diffuse HI envelop. The HI
images reveal disturbed gas kinematics and HI clouds outside the optical extent
of the galaxy, indicating recent tidal interaction or merger in the system. The
results strongly indicate that Mrk 22 is undergoing a chemical and
morphological evolution due to ongoing star formation, most likely triggered by
a merger.
