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NGC7793, NGC300, M33 and NGC2403 are four nearby undisturbed and bulgelesslow-mass spiral galaxies with similar morphology and stellar mass. They areideal laboratories to study disc formation scenarios and stellar mass growthhistories. We construct a simple chemical evolution model by assuming thatdiscs grow gradually with continuous metal-free gas infall and metal-enrichedgas outflow. By means of the classical $\chi^{2}$ methodology, applied to themodel predictions, the best combination of free parameters capable ofreproducing the corresponding present-day observations is determined, i.e. theradial dependence of the infall timescale $\tau=0.1r/{R_{\rm d}}+3.4\,{\rmGyr}$ ($R_{\rm d}$ is the disc scale-length) and the gas outflow efficiency$b_{\rm out}=0.2$. The model results are in excellent agreement with thegeneral predictions of the inside-out growth scenario for the evolution ofspiral galaxies. About 80\% of the stellar mass of NGC\,7793 is assembledwithin the last 8\,Gyr and 40\% within the last 4\,Gyr. By comparing thebest-fitting model results of the three other galaxies we obtain similarresults, 72\% (NGC300), 66\% (NGC2403) and 79\% (M33) stellar mass wereassembled within the past $\sim\rm 8\,Gyr$ (i.e. $z\,=\,1$). These four discgalaxies simultaneously increase their sizes and stellar masses as time goes byand they grow in size at $\sim\,0.30$ times the rate at which they grow inmass. The scale-lengths of these four discs are now 20\% -- 25\% larger than at$z\,=\,1$. Our best-fitting model predicted the stellar mass-metallicityrelation and the metallicity gradients, constrained by the observedmetallicities from HII-regions emission line analysis, agree well with theobservations measured from individual massive red and blue supergiant stars andpopulation synthesis of SDSS galaxies.

The growth history of local M33-mass bulgeless spiral galaxies