starbursts begin with the formation of stars with a wide range of masses, but for the first 10 myr, the energetics are dominated by radiation and winds of the hottest o-type stars. the integrated galaxy spectra show strong nebular emission lines from the hot excited gas; from 3-6 myr, the most massive stars evolve to form highly evolved wolf-rayet stars, with strong stellar emission line spectra. this phase has been detected in that subset of emission line galaxies called wolf-rayet galaxies. in our previous optical and uv studies of such objects we have identified thousands of o-type stars, (and fewer wolf-rayet stars); these are clustered into smaller, more compact star forming regions. we are observing starburst galaxies at a propitious moment of time when the hottest and most massive stars still dominate the energetics. such relatively nearby systems may be prototypes for the enigmatic ''blue galaxies.. at cosmological distances and/or the even more energetic so-called ir galaxies. we already have good estimates of the hot star populations and the conditions of the ionized gas in a number of w-r galaxies from our previous optical and ultraviolet work. we propose to use the iso sws spectrograph to analyse near ir hii region lines to address the following issues:(1) do we infer similar conditions for the hii region gas from ir lines as from the optical lines? (if dust extinction plays an important role, we might not). (2) what do we infer of the hot star populations in these starbursts from the ir lines, compared to our inferences from shorter wavelengths? (some portions of the starbursts may have hidden from view at short wavelengths). (3) with the understanding of the strengths and pitfalls of near ir nebular emission line analysis we acquire here, we can go forward with confidence to study more heavily reddened starburst systems in which shorter wavelength data are difficult or even impossible to obtain.
Instrument
SWS06
Temporal Coverage
1996-04-24T08:22:58Z/1997-01-07T13:06:53Z
Version
1.0
Mission Description
The Infrared Space Observatory (ISO) was the world's first true orbiting infrared observatory. Equipped with four highly-sophisticated and versatile scientific instruments, it was launched by Ariane in November 1995 and provided astronomers world-wide with a facility of unprecedented sensitivity and capabilities for a detailed exploration of the Universe at infrared wavelengths.
