The role of major mergers in galaxy evolution is investigated through a detailed characterization of the stellar populations , ionized gas properties , and star formation rates ( SFR ) in the early-stage merger LIRGs IC 1623 W and NGC 6090 , by analysing optical Integral Field Spectroscopy ( IFS ) and high resolution HST imaging .
The spectra were processed with the starlight full spectral fitting code , and the emission lines measured in the residual spectra .
The results are compared with control non-interacting spiral galaxies from the CALIFA survey .
Merger-induced star formation is extended and recent , as revealed by the young ages ( 50–80 Myr ) and high contributions to light of young stellar populations ( 50–90 \% ) , in agreement with merger simulations in the literature .
These early-stage mergers have positive central gradients of the stellar metallicity , with an average \sim 0.6 Z _ { \odot } .
Compared to non-interacting spirals , they have lower central nebular metallicity , and flatter profiles , in agreement with the gas inflow scenario .
We find that they are dominated by star formation , although shock excitation can not be discarded in some regions , where high velocity dispersion is found ( 170–200 km s ^ { -1 } ) .
The average SFR in these early-stage mergers ( \sim 23–32 M _ { \odot } yr ^ { -1 } ) is enhanced with respect to main-sequence Sbc galaxies by factors of 6–9 , slightly above the predictions from classical merger simulations , but still possible in about 15 \% of major galaxy mergers , where U/LIRGs belong .