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Most of the chemical evolution models are not very reliable for the last5~Gyr of galactic evolution; this is mainly because abundance gradients foundin the literature show a big dispersion for young objects; a big culprit ofthis is the dispersion found in HII region gradients. Part of this dispersionarises from two different methods used to determine O/H in HII regions: thedirect method (DM), based on forbidden lines; and the temperature independentmethod (TIM), based on permitted lines; the differences between these twomethods are about 0.25~dex. We present two chemical evolution models of ourgalaxy to fit the O/H gradients of HII regions, one obtained from the DM andthe other obtained from the TIM. We find that the model based on the TIMproduces an excellent fit to the observational stellar constraints (B-stars,Cepheids, and the Sun), while the model based on the DM fails to reproducethem. Moreover the TIM model reproduces the flattening observed in the 3-6 kpcgalactocentric range; this flattening is attained with an inside-out starformation quenching in the inner disk starting ~ 9 Gyr ago.

The last 5 Gyr of Galactic chemical evolution based on H II region abundances derived from a temperature independent method