ISO Surveys of a Dusty Universe Proceedings of a Ringberg Workshop H
The unprecedented sensitivity of the Infrared Space Observatory and the far-infrared window provided by IRAS led to spectroscopic surveys throughout the entire infrared region. In particular, the high resolution allowed for pointed observations of individ
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Many of the ISO observers who assembled for this workshop at Ringberg castle met for the third time in the Bavarian Alps. At two previous meetings in 1989 and 1990 surveys were only a minor topic. At that time we were excited by the discoveries of the IRAS survey mission and wanted to follow it up with pointed observations using an observatory telescope equipped with versatile instruments. With the rapid development of detector arrays and stimulated by ISO’s Observing Time Allocation Committee, however, surveys eventually became an issue for the upcoming mission. In a review paper on “Infrared Surveys - the Golden Age of Exploration” given at an IAU meeting in 1996, Chas Beichman already mentioned that there are ISO surveys. They were at the bottom of his hit list, while the winners were future space missions (Planck, SIRTF, etc.) and ground-based surveys in preparation (Sloan, 2MASS, DENIS, etc.). He organized his table according to the relative explorable volume, calculated from the solid angle covered on the sky and the maximum distance derived from the detection sensitivity. Clearly, with this figure of merit, ISO, as a pointed observatory, is rated low. Applying the classical definition of a survey, i.e. to search in as large a volume as possible for new or rare objects and/or study large numbers of objects of various classes in order to obtain statistical properties, ISO was indeed limited. As is usual in an observatory mission, hundreds of observers competed with hundreds of proposals, therefore only limited samples of certain objects could be allocated to individuals. However, if we extend the definition of a survey to include the investigation of reasonable samples of similar objects, then ISO was indeed a great survey mission. For the first time on a cooled space mission, the observatory offered several unique capabilities: • Mid-infrared deep imaging with unprecedented sensitivity. • 200 μm mapping with a spatial resolution comparable to that of IRAS at 100 μm. • Similar sensitivity to COBE but much higher spatial resolution for exploration of the far-infrared extragalactic background. • High and low spectral resolution capabilities over the wide wavelength range of 2 – 200 μm. • Far-infrared polarization studies.
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Preface
• Complementary surveys performed with “no cost” of observing time in parallel to the main instrument or during slews or to fill small gaps in the scheduled observations. The ISOCAM surveys at 15 μm and the ISOPHOT surveys at 170 μm have revealed many new sources in the distant universe. This has impressively demonstrated that even with a 60-cm telescope, if cooled, important cosmological questions, such as star formation history in the young universe, can be addressed. The infrared is a key region for this research because many of these young galaxies are dust-enshrouded. In addition, ISO has delivered many template spectra for luminous galaxies such as ULIRGs, starbursters, and AGNs throughout the whole infrared wavelength region. ISO data already place serious constraints on the gal
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