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The effects of rotation on stellar evolution are particularly important atlow metallicity, when mass loss by stellar winds diminishes and the surfaceenrichment due to rotational mixing becomes relatively more pronounced than athigh metallicities. Here we investigate the impact of rotation and metallicityon stellar evolution. Using a similar physics as in our previous large grids ofmodels at Z=0.002 and Z=0.014, we compute stellar evolution models with theGeneva code for rotating and nonrotating stars with initial masses (Mini)between 1.7 and 120 Msun and Z=0.0004 (1/35 solar). This is comparable to themetallicities of the most metal poor galaxies observed so far, such as I Zw 18.Concerning massive stars, both rotating and nonrotating models spend most oftheir core-helium burning phase with an effective temperature higher than 8000K. Stars become red supergiants only at the end of their lifetimes, and fewRSGs are expected. Our models predict very few to no classical Wolf-Rayet starsas a results of weak stellar winds at low metallicity. The most massive starsend their lifetimes as luminous blue supergiants or luminous blue variables, afeature that is not predicted by models with higher metallicities.Interestingly, due to the behavior of the intermediate convective zone, themass domain of stars producing pair-instability supernovae is smaller atZ=0.0004 than at Z=0.002. We find that during the main sequence phase, theratio between nitrogen and carbon abundances (N/C) remains unchanged fornonrotating models. However, N/C increases by factors of 10-20 in rotatingmodels at the end of the MS. Cepheids coming from stars with Mini > 4-6 Msunare beyond the core helium burning phase and spend little time in theinstability strip. Since they would evolve towards cooler effectivetemperatures, these Cepheids should show an increase of the pulsation period asa function of age.

Grids of stellar models with rotation IV. Models from 1.7 to 120 Msun at a metallicity Z = 0.0004