SIMBAD references

In general, Hii regions do not show clear signs of self-enrichment in products from massive stars (M ≥ 8M_☉). In order to explore why I modelled the contamination with Wolf-Rayet star ejecta of metal-poor (Z = 0.001) Hii regions, ionized either by a 10⁶M_☉cluster of coeval stars (cluster 1) or by a cluster resulting from continuous star formation at a rate of 1M_☉/yr (cluster 2). The clusters have Z = 0.001 and a Salpeter initial mass function from 0.1 to 120M_☉. Independent one-dimensional constant density simulations of the emission-line spectra of unenriched Hii regions were computed at the discrete ages 1, 2, 3, 4 and 5Myr, with the photoionization code cloudy, using as input, radiative and mechanical stellar feedbacks predicted by the evolutionary synthesis code starburst99. Each Hii region was placed at the outer radius of the adiabatically expanding superbubble of Mac Low & McCray. For models with thermal and ionization balance time-scales of less than 1Myr, and with oxygen emission-line ratios in agreement with observations, the volume of the superbubble and the Hii region was uniformly and instantaneously polluted with stellar ejecta predicted by starburst99. I obtained a maximum oxygen abundance enhancement of 0.025dex, with cluster 1, at 4Myr. It would be unobservable.