The most rapidly evolving regions of galaxies often display complex optical spectra with emission lines excited by massive stars , shocks and accretion onto supermassive black holes .
Standard calibrations ( such as for the star formation rate ) can not be applied to such mixed spectra .
In this paper we isolate the contributions of star formation , shock excitation and active galactic nucleus ( AGN ) activity to the emission line luminosities of individual spatially resolved regions across the central 3 \times 3 kpc ^ { 2 } region of the active barred spiral galaxy NGC 613 .
The star formation rate and AGN luminosity calculated from the decomposed emission line maps are in close agreement with independent estimates from data at other wavelengths .
The star formation component traces the B-band stellar continuum emission , and the AGN component forms an ionization cone which is aligned with the nuclear radio jet .
The optical line emission associated with shock excitation is cospatial with strong H _ { 2 } and [ Fe II ] emission and with regions of high ionized gas velocity dispersion ( \sigma \ga 100 km s ^ { -1 } ) .
The shock component also traces the outer boundary of the AGN ionization cone and may therefore be produced by outflowing material interacting with the surrounding interstellar medium .
Our decomposition method makes it possible to determine the properties of star formation , shock excitation and AGN activity from optical spectra , without contamination from other ionization mechanisms .