Activity and quiescence in galaxies at redshifts 1.4 < z <3 .5. The role of the starburst temperature (Research Note)

We investigate “activity” and “quiescence” in galaxies at relatively high redshifts by modelling the line (and continuum) spectra of each object. The models account consistently for photoionization and shocks. We claim that the starburst effective temperature, the flux from an AGN, and the shock velocity are critical to activity. The results confirm that two sample galaxies show intense starburst activity with temperatures reaching T∗ = 2 × 10 5 K and shock velocities Vs > 250 km s −1 , while for the remaining galaxies in our sample, the models show quiescent star formation with T∗ ≤ 7 × 10 4 K. A Seyfert 2-like AGN is proposed in one galaxy. The O/H relative abundances derived by the detailed modelling of the spectra are nearly solar for all the sample galaxies, in contrast to those obtained by direct methods.