Abstract
Spectroscopic observations of a massive star formation in the ultraviolet and their interpretation are reviewed. After a brief historical retrospective, two well-studied resolved star clusters and the surrounding H II regions are introduced: NGC 2070 in the Large Magellanic Cloud and NGC 604 in M33. These regions serve as a training set for studies of more distant clusters, which can no longer be resolved into individual stars. Observations of recently formed star clusters and extended regions in star-forming galaxies in the nearby universe beyond the Local Group are presented. Their interpretation relies on spectral synthesis models. The successes and failures of such models are discussed, and future directions are highlighted. I present a case study of the extraordinary star cluster and giant H II region in the blue compact galaxy II Zw 40. The review concludes with a preview of two upcoming Hubble Space Telescope programs: ULLYSES, a survey of massive stars in nearby galaxies, and CLASSY, a study of massive star clusters in star-forming galaxies.
Highlights
A Brief Retrospective of the Pre-Hubble TimesThe space-ultraviolet (UV) wavelength region became accessible to spectroscopic observations in the 1960s
These observations were restricted to bright stars; UV spectra of extragalactic star clusters and star-forming galaxies could not be collected until the launch of the International Ultraviolet Explorer (IUE) satellite, which had the capability of obtaining multi-hour exposures necessary for extragalactic studies [2]
The strong P Cygni lines in stellar winds are mostly resonance transitions, which implies that they are strong in the interstellar medium (ISM) as well and can contribute to the features seen in Figure 2 [8]
Summary
The space-ultraviolet (UV) wavelength region became accessible to spectroscopic observations in the 1960s At this time, the introduction of the 3-axis star-pointing stabilization system on Aerobee sounding rockets enabled the acquisition of sufficiently deep spectrograms of astronomical objects outside the solar system [1]. The introduction of the 3-axis star-pointing stabilization system on Aerobee sounding rockets enabled the acquisition of sufficiently deep spectrograms of astronomical objects outside the solar system [1] These observations were restricted to bright stars; UV spectra of extragalactic star clusters and star-forming galaxies could not be collected until the launch of the International Ultraviolet Explorer (IUE) satellite, which had the capability of obtaining multi-hour exposures necessary for extragalactic studies [2]. At a distance of 5.1 Mpc, NGC 1705 is one International
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