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We use the growing data sets of very-metal-poor stars to study the impact ofstellar winds of fast rotating massive stars on the chemical enrichment of theearly Galaxy. We use an inhomogeneous chemical evolution model for the Galactichalo to predict both the mean trend and scatter of C/O and N/O. In one set ofmodels, we assume that massive stars enrich the interstellar medium during boththe stellar wind and supernovae phases. In the second set, we consider that inthe earliest phases (Z <10^-8), stars with masses above 40 Msun only enrich theinterstellar medium via stellar winds, collapsing directly into black holes. Wepredict a larger scatter in the C/O and N/O ratios at low metallicities whenallowing the more massive fast-rotating stars to contribute to the chemicalenrichment only via stellar winds. The latter assumption, combined with thestochasticity in the star formation process in the primordial Galactic halo canexplain the wide spread observed in the N/O and C/O ratios in normalvery-metal-poor stars. For chemical elements with stellar yields that dependstrongly on initial mass (and rotation) such as C, N, and neutron captureelements, within the range of massive stars, a large scatter is expected oncethe stochastic enrichment of the early interstellar medium is taken intoaccount. We also find that stellar winds of fast rotators mixed withinterstellar medium gas are not enough to explain the large CNO enhancementsfound in most of the carbon-enhanced very-metal-poor stars. In particular, thisis the case of the most metal-poor star known to date, HE 1327-2326, for whichour models predict lower N enhancements than observed when assuming a mixtureof stellar winds and interstellar medium. We suggest that these carbon-enhancedvery metal-poor stars were formed from almost pure stellar wind material,without dilution with the pristine interstellar medium.

The effects of stellar winds of fast-rotating massive stars in the earliest phases of the chemical enrichment of the Galaxy