Fe b 20 02 Optical spectroscopy of metal - rich H II regions and circumnuclear hot spots in M 83 and NGC 3351

We present optical spectroscopy of a sample of metal-rich extragalactic H II regions in the spiral galaxies M83 (NGC 5236), NGC 3351 and NGC 6384. The metal abundance, estimated from semi-empirical methods using strong emission lines, is found to be above solar for most of the objects. The sample includes a number of circumnuclear H II regions (hot spots), which are found in general to have spectral properties similar to the H II regions located in the disks. Different age estimators (equivalent width of the Hβ emission line W (Hβ), Balmer line absorption profiles, UV spectra) provide consistently young ages (4-6 Myr) for the hot spots. We have detected the W-R bump feature at 4650 Å in five of the objects, and in fewer cases possibly the WC features in the red at 5696 Å and 5808 Å. Six additional objects showing W-R features are drawn from our previous work on extragalactic H II regions. From the measured luminosity of the stellar He IIλ 4686 Å line we estimate a small number of WN stars (from 1-2 to about 30). We have compared the measured intensities and equivalent widths of the W-R bump to the predictions of recent evolutionary models for massive stellar populations. By assuming instantaneous bursts of star formation the ages derived from W (Hβ), between 3 and 6 Myr, are in agreement with the age span predicted by the models. The observed strength of the W-R bump is in agreement with the predictions for only half of the objects, the remainder showing lower I(4650)/I(Hβ)