The detailed radial velocity field of the H II region N105, in the LMC, has been obtained for the Hα and [O III] 5007 lines with a spatial sampling of 9″ and a spectral sampling of 16 and 7kms−1. The peculiar velocity field and morphology indicate that N105 contains four bubble shaped nebulae and two bright distinct quasi-spherical H II regions, more or less coeval, embedded inside another large shell nebula. They are essentially formed by the action of stellar winds of a few exciting stars, born deep inside their parental cloud. This result is deduced from the energy input inside the ionized gas by the stellar winds of early type stars and from dynamical simulations combining the effects of stellar winds with those of high density gradients inside the neutral gas. The size and morphology of the H II region are conditioned by the depth inside the natal cloud; the observed dynamical time-scale of the H II region starts at the moment of blow-out of the molecular cloud.

We have begun a search for emission-line stars toward the inner Galaxy using narrow-band photometry centered on the emission lines of He I 2.06μm, C IV 2.08μm, H I Brγ 2.166μm and He II 2.189μm. The census of Wolf-Rayet and other emission-line stars in the Galaxy is incomplete, owing to the large extinction at optical and shorter wavelengths toward the inner Galaxy. However, these massive, evolved stars are bright and can be detected at large distances in the near infrared.

In this work we report the search for nebulosities associated with the candidate Wolf-Rayet stars listed in Massey el al (1992) in the irregular galaxy IC 10, based upon Hα, [S II], and [O III] direct images and imaging Fabry-Pérot spectroscopy. Approximately 95% of the WR candidate stars we analyzed are found within nebulae. For most of these nebulae, we find broad wings on their Hα radial-velocity profiles. For some of the nebulae, the Hα velocity profiles are broadened with a typical velocity difference of 80–100 kms1.

The Galactic Centre (GC) region has in recent years attracted a lot of attention from the hot star community following the discovery of numerous He I emission line sources (Krabbe et al. 1991). Recent studies (e.g., Najarro et al. 1994) revealed stellar properties reminiscent of cool Wolf-Rayet stars, providing clues to the origin of the Lyman and He+ ionizing fluxes, and the luminosity in the central parsec of our galaxy. They allow the recent star formation history to be unveiled, and assess the effect of high metallicity on massive star evolution.

We present results of an HST archive study of the star cluster NGC 3603. The color-magnitude diagram (CMD) and the radial profiles have been derived using HST-nicmos F110W and F171M images. As expected, the CMD shows that the cluster is very young (< 3 Myr) and that a significant portion of the stellar population (M < 4M⊙) is on the pre-main sequence phase. From the radial profiles, we derive a similar half-light radius for both wavebands of 0.17 pc.

We present results from new HST imaging and spectroscopy of the peculiar Large Magellanic Cloud H II region N 44C and its ionizing star. While this nebula exhibits strong He II recombination emission, the source of the He+ ionizing photons has not been found. The UV spectrum of the ionizing star suggests an approximate spectral class of 07–08; the UV Si IV, He II, and N IV features do not show P-Cygni profiles, indicating that the ionizing star is not a supergiant. No companion star has yet been detected. Ground-based and HST optical spectroscopy of the ionized gas shows that the nebular abundances of C, N, O and He are not anomalous relative to other LMC H II regions, suggesting that no previous WR/SN companion has disappeared. Echelle spectroscopy has also ruled out the presence of high velocity shocked gas. Deep ROSAT imaging shows no X-ray point source in this location. The “fossil X-ray binary” hypothesis of Pakull & Motch (1989) remains the best explanation for the ionization of this nebula; however, convincing evidence for this hypothesis remains elusive.

The heavily-reddened Local Group galaxy IC 10 has been studied at narrow-band emission-line wavelengths and in U, B, V, and I with the APO 3.5m telescope. The four-color data are being used to measure and map the foreground and internal reddening. The color-magnitude diagram clearly isolates the main sequence from the red supergiants and from the abundant foreground stars. The absolute magnitudes of the main sequence stars, together with the anomalously-abundant WR stars reported by Massey & Armandroff, indicate that the galaxy is currently undergoing a fairly extensive burst of star-formation.

We present a preliminary analysis of HST images of the Local Group galaxy IC 10. IC 10 has an unusual Wolf-Rayet star population and is believed to be undergoing a starburst. Nevertheless, stars to at least 6.5 M⊙ are seen and the young star clusters are comparable in richness and spatial concentration to LMC populous clusters.

We present first results of fully synthetic UV spectra of young starbursts. With this we mean that the spectra used to model the OB and WN stars result from unified non-LTE model atmospheres, in which stellar winds are accounted for. An important aim of this project is to construct meaningful models for young starbursts at low metallicities. We discuss the presence of He II emission as a function of maximum initial mass and age of the burst.

We compute photo-ionization models for the giant extragalactic H II region NGC 2363, and compare them with optical observational data. We focus on the following observational constraints: F(Hβ), Ne, EW(Hβ), and the ratios of I(λ 5007), I(λ 4363), I(λ 3727), I(λ 6300), I(λ 6720) and I(λ 4686) relative to I(Hβ). We discuss the variations of the emission spectra obtained with different input parameters. We show that low metallicity models (Z = 0.10Z⊙) cannot reproduce the observed features of the spectrum, and that the disagreement can be satisfactorily overcome by allowing for spatial temperature fluctuations in the nebula. Accordingly, we show that the metallicity of NGC 2363 has most probably been underestimated, and that a value of Z ≃ 0.25 Z⊙ is in better agreement with the observational data than the usually adopted value Z≃0.10Z⊙. We also derive values for the slope and the high mass end of the IMF, as well as the age of the stellar cluster.

We study the properties of the young population of NGC 604 and find evidences for 1–2 Myr differences between different regions. Four of the eleven WR stars in NGC 604 are found to have wide Hα emission lines. None of the WR stars is located within knots of high density, high excitation gas, as opposed to some of the O-type stars.

Recent progress in model atmospheres for hot stars is presented. The impact of nlte wind-blanketed models is shown by comparison with the ‘old’ standard model. In order to confindently use the IR-spectra of objects at the Galactic Center (with high extinction) to derive their physical properties and trace the metal content, the consistency between results from optical and IR analysis is checked in a calibration study using the B1.5Ia+ star HDE 316285. With the above consistency proved, we started a detail investigation of the Pistol Star. Preliminary results are presented.

Studies of extragalactic (un-resolved) H II regions, usually rely on assumptions about the underlying stellar absorption to estimate the reddening corrections needed to derive physical conditions of the ionized gas and to infer parameters of the ionizing stars (Robledo-Rella & Firmani 1990). We have addressed the problem of estimating quantitatively the effects of the hot star spectra on derived physical (nebular and stellar) parameters of galactic H II regions.

A new method is used to determine masses, ages, and reddening for the stars of the starburst cluster NGC 2070 in 30 Doradus. The data are consistent with a star-formation rate which increases exponentially with a characteristic rise time of 1.7 Myr, independent of mass, starting 7 Myr ago. The IMF is consistent with a single power law IMF with Salpeter slope over the whole 3 M⊙ < M < 120 M⊙ range investigated, with evidence for flattening for the innermost radial bin.

Infrared observations of young massive stars yield crucial insights on the birth of high-mass stars and their interaction with the parent molecular cloud. Results for IRAS23140+6121, G254.681+0.219, and NGC6334F obtained by near- and mid-infrared imaging are presented for a brief illustration.

NGC 3603 is the most massive optically visible H II region in our Galaxy and is considered to be the Galactic analogue to 30 Doradus and, thus, a prototype of the starburst phenomenon. Its core, known as WR 43 (HD 97950), contains several dozens of O-B0 stars within 35″. These have been studied with very high resolution in the optical and near-IR. Melnick, Tapia & Terlevich (1989) concluded that the starburst cluster has an age spread of 1 to 2 Myr and that its boundaries extend to ∼60″, while Eisenhauer et al. (1998) determined that the lower mass stars in the core are younger than 1 Myr.

Aimed at identifying supersoft X-ray sources in ionization nebulae, we have searched for extended optical emission within the X-ray error boxes of the 15 supersoft sources in M31 (Greiner et al. 1996). One optical nebula was found, of which we obtained spectroscopy, narrow-band imaging and FP-interferometry, to determine its relation to the positionally correlated supersoft X-ray source RX J0045.5+4206. M31 has been surveyed several times with different goals. Baade & Arp (1964) compiled a list of 688 emission nebula in M 31. One of these nebulae, BA1-642 (PAV 78915 in the catalog of Pellet et al. 1978), was found by cross-correlation with supersoft X-ray sources. The central object MLA 1159 of this nebula has been classified WR (Meyssonier et al. 1993). Here we confirm this new WR star and discuss the star as well the ring-like nebula around it. We did direct imaging of RX J0045.4+4206 with narrow-band nebular filters, spectroscopy of the central star and surrounding nebulae, and we observed the nebula with the FP-interferometer PUMA. All observations were carried out at OAN SPM, México.

The extensive ‘second generation’ of star formation within the 30 Doradus Nebula, evidently triggered by the R136 central cluster around its periphery, has been imaged with HST-NICMOS. Many new infrared sources and structures are found in these images.

We have conducted a systematic search for nebulae surrounding Wolf-Rayet stars in M31, where 28 objects are found.

Wolf-Rayet galaxies are those starburst systems in which the presence of Wolf-Rayet stars is inferred from the appearance of broad emission lines, notably λ4686 HeII. The ages of the bursts are only a few Myr when WR stars are present. Many (all?) of these starburst galaxies are interacting or merging systems. This talk will review the methods used to estimate the hot star populations in these galaxies, with emphasis on optical spectrophotometry. It will be important to keep in mind that the discovery of WR stars in starburst galaxies is highly dependent on spectral resolution, signal to noise, and the local properties of the object since one is searching for broad but weak emission lines superimposed upon a galaxy continuum. A brief comparison of the inferred numbers of O-type and WR stars in a galaxy, compared to the predictions of the most recent burst models, reveals good agreement in most cases. The exceptions might be understood in terms of geometric dilution (i.e., the stars and the ionized nebular gas are not co-spatial).