We present preliminary results on multi-wavelength observations of the Wolf-Rayet Blue Compact Dwarf Galaxy He2–10. These observations include Hα and continuum imaging, high-resolution Hα spectroscopy, high-resolution radio-continuum mapping at 6.3 and 3.5 cm and X-ray mapping. The deep Hα image reveals that the galaxy consists of a complex system of different star-forming knots surrounded by kpc-scale bubble-like and filamentary structures. The most interesting structure is a bipolar superbubble centered on the most intense star-formation knot. High-resolution spectroscopy of this structure indicates that it is expanding with a velocity in the range 75–250 km s−1. This kind of outflows is likely to be produced by the mechanical action of stellar winds and supernovae explosions in the intense starbursts that the galaxy hosts. This scenario is consistent with the finding of a very steep radio spectral index in the extended radio continuum emission (α = −0.59) that confirms the presence of a large number of supernova remnants in the galaxy.

We optically find an unusual emission-line bubble near the tip of the southeastern arm of NGC 7318B. A large number (∼ 106) of supernova remnants would be the most plausible agents.

We present some results on the burst properties in star forming galaxies, using near infrared stellar features typical of red supergiants and Brackett nebular lines which trace the presence of luminous H II regions.

We performed a search of Wolf-Rayet stars features in optical spectra of two large samples of H II regions and H II galaxies. The main results are a list of galaxies/regions containing WR stars (of which seven are new WR galaxies) and a second list of possible WR galaxies/regions with WR stars.

Three new ultraviolet spectral libraries of massive, hot stars using high and medium resolution spectra of objects located in the solar neighbourhood and the Magellanic Clouds are presented. Massive stars display unique wind signatures which are relatively easy to study in the ultraviolet. These libraries are crucial tools when investigating the massive stellar population of distant star-forming galaxies.

We present preliminary results of the kinematics of the Wolf-Rayet galaxy pairs: NGC 1741 and NGC 7714/7715.

We report on an ongoing survey of the X-ray properties of Wolf-Rayet galaxies. The current sample now has 14 detections, as well as a number of upper-limits. WR galaxies have soft thermal X-ray spectra with properties consistent with an origin from superbubbles in a young starburst.

We present preliminary results of our near-infrared JHK images of a sample of H II galaxies observed at UKIRT. The presence of knots of enhanced emission in the near-IR may indicate the existence of luminous super star clusters which will serve to unveil the basic units which constitute the starburst phenomenon in galaxies. Based on near-IR colours we will further discuss the history of star formation in these bursting dwarf galaxies.

Using a population number synthesis code and detailed massive star evolutionary calculations, we investigate the effect of close binary evolution on Hα and Hβ emission-line strength variation in starburst regions. The Hβ line strength especially, is considered as a good age indicator. We demonstrate that the formation of rejuvenated accretion stars (Blue Stragglers) through RLOF lengthens the life-time of the Hβ flux and makes the age determination of a starburst regions ambiguous. We separately calculate the effect of Wolf-Rayet stars and of X-ray binaries on Hα and Hβ and conclude that both are of minor importance.

II Zw 33 is a gas-rich Wolf-Rayet galaxy with a low surface-brightness companion galaxy. Neither II Zw 33 nor its companion need any dark matter in order to explain the observed rotation curves. The available observations support a scenario in which the companion has triggered the current burst of star formation in II Zw 33.

On scales ranging from pcs to kpcs, the relationship between stellar and gaseous galactic components forms the basis for interpreting observations of galaxies and understanding galaxy formation and evolution. Feedback effects from massive stars dominate the structure, ionization, kinematics, and enrichment of the gaseous ISM in star-forming galaxies. On galactic scales, the ionizing radiation from these stars creates populations of H II regions and the diffuse, warm ionized medium. Likewise, superbubbles created by stellar winds and supernovae strongly influence the structure, kinematics, and balance of the multiphase ISM. This contribution reviews these feedback effects of massive stars on the global ISM.

Neutral hydrogen (H I) is a magnificent tool when studying the structure of the interstellar medium (ISM) as it is relatively easily observable and can be mapped at good spatial and velocity resolution with modern instruments. Moreover, it traces the cool (∼ 100 K) and warm (∼ 5000 K) neutral gas which together make up about 60%, or the bulk, of the ISM. The currently accepted picture is that stellar winds and subsequent supernovae are the origin for the clearly defined holes or bubbles within the more or less smooth neutral medium. The H I can therefore serve indirectly as a tracer of the hot interstellar medium (HIM) left behind after the most massive stars within an OB association have gone off as supernovae. A splendid example is the dwarf galaxy IC 2574 for which we discuss H I, optical and X-ray observations.

I discuss the observational evidence that starburst galaxies are able to drive galactic-scale outflows ('superwinds') and then argue generally that superwinds must have had an important role in galaxy evolution. To explore the role of feedback from massive stars, I review results suggesting that starbursts seem to obey a limiting IR surface brightness of about 1011 L⊙ kpc−2, corresponding to a maximum star-formation rate of about 45M⊙ yr−1kpc−2 for a ‘normal’ initial mass function. I conclude by discussing the role of winds in determining this upper-limit and discuss recent results implying that winds might actually escape the galactic potentials in which they reside.

We summarize the goals of photo-ionization modelling of nebulae ionized by Wolf-Rayet stars and discuss the methodology. We present some examples in different astrophysical contexts: ring nebulae around massive WR stars, planetary nebulae with [WR]-type central stars, and giant H II regions with WR stars. We discuss in more detail a work in progress (Stasińska & Schaerer 1999) on the galaxy I Zw 18.

We present some results of an observational programme devoted to obtain deep imagery and high-resolution spectroscopy for a sample of dwarf Wolf-Rayet galaxies. Our main result is that interaction with fainter optical companions could be the origin of the strong star formation episodes observed in, at least, an important fraction of the objects. In all the cases presented, the companions and the signatures of interaction or merging can only be detected when deep and detailed observations are taken. We predict that the fraction of dwarf WR galaxies (or even H II galaxies in general) with interacting signatures will increase when detailed observations for more objects are available.

The warm ionized gas in low-mass, metal-poor star forming galaxies is chemically homogeneous despite the prevalence of large H II regions which contain hundreds of evolved massive stars, supernovae, and Wolf-Rayet stars with chemically-enriched winds. Galaxies with large WR star content are chemically indistinguishable from other vigorously star-forming galaxies. Furthermore, no significant localized chemical fluctuations are present in the vicinity of young star clusters, despite large expected chemical yields of massive stars. An ad hoc fine-tuning of the release, dispersal and mixing of the massive star ejecta could give rise to the observed homogeneity, but a more probable explanation is that fresh ejecta from massive stars reside in a hard-to-observe hot or cold phase. In any case, the observed chemical homogeneity indicates that heavy elements which have already mixed with the warm interstellar medium (thus accessible to optical spectroscopy) are homogeneously dispersed over scales exceeding 1 kpc. Mixing of fresh ejecta with the surrounding warm ISM apparently requires longer than the lifetimes of typical H II regions (> 107 yr). The lack of observed localized chemical enrichments is consistent with a scenario whereby freshly-synthesized metals from massive stars are expelled into the halos of galaxies in a hot, 106 K phase by supernova-driven winds before they cool and ‘rain’ back down upon the galaxy, creating gradual enrichments on spatial scales >1 kpc.

We will review the most popular models for the chemical evolution of some starburst galaxies, in particular dwarf irregular galaxies. These galaxies are relatively simple and unevolved objects with low metallicities and large gas contents, suggesting that they are either young or have undergone discontinuous star formation activity. Some dwarf irregulars are starburst galaxies currently experiencing an intense star formation event and they are known as blue compact galaxies or extragalactic H II regions. We will discuss the effects of the presence of dark matter halos together with stellar energetics (stellar winds and supernovae) on the development of a galactic wind in these systems. Particular emphasis will be given to the role of massive stars in driving the thermal and chemical evolution of the gas, in particular to type II supernovae. A comparison between different model predictions for abundances and abundance ratios will be used to impose constraints on the star formation history and on the amount of dark matter, which we found to be extremely important in these systems.

Owing to their large luminosities per unit mass H II galaxies allow us to investigate in considerable detail the process of high mass star formation out to redshifts of cosmological importance. In this contribution we discuss the calibration of the correlation between the Hβ luminosity and the emission line width of H II galaxies as a distance indicator. We show that H II galaxies can be reliably used as distance indicators out to redshifts z > 3 provided that their line widths and fluxes can be determined with accuracies better than 10%.

I review the evidence for a possible connection between AGN and starbursts and assess the energetic role of massive stars in the AGN phenomenon. My particular focus is on UV spectroscopy, since this is the energetically dominant spectral regime for the hot high-mass stars that power starbursts, and contains a wealth of spectral features for diagnosing the presence of such stars. I also review the non-stellar sources of UV line and continuum emission in AGN, including scattered or reprocessed light from the ‘central engine’. Spectroscopy directly shows that hot stars provide most of the UV light in about half of the brightest type 2 Seyfert nuclei and UV-bright LINERS. The population of hot stars in these AGN is typically heavily extinct and reddened by dust with A(1600Å) ≃ 2–4 mag. The implied intrinsic UV luminosities of the starburst range from 108 to 109 L⊙ in the LINERS to 1010 to 1011 L⊙ in the type 2 Seyferts. Massive stars play an energetically significant role in many AGN, but the causal or evolution connection between starbursts and AGN is unclear. I also consider the energetics of massive stars and accreting supermassive black holes from a global, cosmic perspective. Recent inventories in the local universe of the cumulative effect of nuclear burning (metal production) and of AGN-fueling (compact dark objects in galactic nuclei) imply that accretion onto supermassive black holes may have produced as much radiant energy as massive stars over the history of the universe.

Among the Active Galactic Nuclei that have suffered type mutations, the classically classified Seyfert 2 NGC 7582 recently found at a Seyfert 1 stage, is perhaps one of the most puzzling cases, since it defies a well supported case for unification. We investigate the possibility that this type transition, common to another twelve AGN, is driven by supernovae exploding in a nuclear/circumnuclear starburst.