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In this work we investigate the stellar content of three circumnuclear giant H II regions in the starburst galaxy NGC 7714. We model the stellar population that best reproduces the observational constraints given by the Ha image and the optical spectroscopy from 3710 to 9700 Ó. In this paper we address a robust method for analyzing the stellar content of giant extragalactic H II regions (GEHRs) as a Ðrst step in a strategy that should allow us to understand better how star formation proceeds. To test the power of the method, we have chosen three very well-studied regions in which many observational constraints are known. The models reproduce simultaneously the observed sizes derived from the Ha image, the emission-line spectrum from the gaseous component, and the optical features from the massive stars such as Wolf-Rayet bumps in emission, and the near-infrared calcium triplet, CaT, in absorption when detected. We Ðt the stellar populations through evolutionary synthesis models plus the photoionization code CLOUDY, under the assumption of a shell geometry for the regions. This approach allows us to derive the physical properties of the star clusters, such as mass, age, and metallicity, inside these GEHRs. The method is based on previous work of a complete grid of photoionization models for giant H II regions ionized by evolving star clusters of di †erent metallicities (from 0.05 to 2.5 times solar) and ages between 1 and 5.4 Myr. For the present work, we have followed the cluster evolution further, even after the ionization phase has come to an end, in order to reproduce the observed values of the continuum luminosity at 9000 and the equivalent widths of Hb in emission and CaT in absorption. Ó From the results, we Ðnd in two of the three studied regions that a single ionizing stellar burst is sufficient to explain all the observational constraints if no reddening is a †ecting the cluster continuum. Otherwise, the observed values of the Hb equivalent widths imply the existence of an older component. In this latter case, we Ðnd that a model in which two bursts of star formation are considered, a young ionizing one, with ages 3È5 Myr and an older one of 7È9 Myr, that can reproduce the observations. In the third region, the presence of CaT in the near-IR indicates the presence of a non-ionizing population, whose origin is thoroughly discussed.

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We present long‐slit observations in the optical and near‐infrared of eight H ii regions in the spiral galaxy NGC 4258. Six of the observed regions are located in the south‐east inner spiral arms, and the other two are isolated in the northern outer arms. A detailed analysis of the physical conditions of the gas has been performed. For two of the regions, an electron temperature has been derived from the [S iii] λ6312 line. For the rest, an empirical calibration based on the red and near‐infrared sulphur lines has been used. The oxygen abundances derived by both methods are found to be significantly lower (by a factor of 2) than previously derived by using empirical calibrations based on the optical oxygen lines. In the brightest region, 74C, the observation of a prominent feature caused by Wolf–Rayet (WR) stars provides an excellent constraint over some properties of the ionizing clusters. In the light of the current evolutionary synthesis models, no consistent solution is found to explain at the same time both the WR feature characteristics and the emission‐line spectrum of this region. In principle, the presence of WR stars could lead to large temperature fluctuations and also to a hardening of the ionizing radiation. None of these effects is found in region 74C, for which the electron temperatures found from the [S iii] λ6312 line and the Paschen discontinuity at 8200 Å are equal within the errors, and the effective temperature of the ionizing radiation is estimated at around 35 300 K. Both more observations of confirmed high‐metallicity regions and a finer metallicity grid for the evolutionary synthesis models are needed in order to understand the ionizing populations of H ii regions.