The EUV background, the interstellar medium, and ROSAT

Abstract

This is a review of work done by several people in the UK Interstellar Medium/Diffuse Emission ROSAT Special Interest Group. ROSAT is a joint German/American/British project to survey the sky in the X-ray/EUV wavelength region, and to perform Guest Observer pointed observations. The ROSAT Wide Field Camera (WFC) is fully described in the article by Wells et al. (1990). The UK provided the WFC, and it is the preliminary results from this instrument on which the review focuses. In order to encompass the WFC results, the title of the meeting should not be taken too literally, since the WFC operates in the range around 60 to 200 J~. Figure 1 shows both the energy range and the wavelength range of the two WFC survey filters, S1 (0.10 keV 0.18 keV) and $2 (0.085 keV 0.111 keV). Also included in figure 1 are the ranges for the Wisconsin B, C, and Be filters (McCammon et al., 1983; Bloch et al., 1986), and the Einstein satellite low energy filter. The WFC S1 filter is similar to the Wisconsin B illter, but with a slightly lower mean passband energy, and the WFC $2 filter is similar to the Wisconsin Be filter. The main difference between the two systems is resolution: the WFC has a resolution of 3.5 aremln, which is much better than that of the Wisconsin data.