Table of Contents

Executive summary

Ultraviolet Astronomy: Imaging and Spectroscopy

Group Chair: Laurent Drissen, Université Laval

The objective of the DWG on ultraviolet (UV) astronomy is to promote the continued development of UV space astronomy in Canada, and in particular UV spectroscopy. The UV region (110 - 320 nm), which is only accessible from space, is extraordinarily rich in spectroscopic diagnostics of the plasmas found in a wide variety of astronomical objects and environments. The ultraviolet spectral domain remains one of the most important Windows to the Universe, in which Canadian scientific expertise is widely recognized.

However, it is profoundly disturbing that there are no credible plans to maintain access to this astrophysically crucial window to the Universe beyond the May 2009 Servicing mission to the Hubble Space Telescope. Since no other national space agency is currently building a UV telescope with spectroscopic capabilities, the DWG explored ways of using Canadian expertise, both in academia and the industry, to maintain access to this crucial waveband. While the closing of the UV window to high-resolution spectroscopy represents a looming disaster for quantitative astrophysical analysis by astronomers world-wide, it also becomes a tremendous opportunity for the Canadian astronomical community and the CSA to become true leaders in space astronomy.

The DWG has identified five key science areas that define the design of a future spectroscopic UV observatory, namely : (1) Wind and mass-loss properties of hot, massive stars; (2) Chromospheric activity and mass loss in cool stars; (3) Precise determination of stellar masses in binaries; (4) The evolution of starburst galaxies; (5) The variability of active galactic nuclei. Because of substantial improvements in detector technology over the past years, significant breakthroughs in these topics can be reached with a well-designed, modest-size, dedicated space telescope.

The DWG has explored two paths to reach the above-mentioned objectives, namely the development of a Canadian UV spectroscopic satellite and the participation in a large, multi-purpose, international telescope.

In order to fully benefit from the academic and industrial expertise now available in Canada, the DWG recommends that conceptual studies of a modest-size (0.5 - 1.0-m primary mirror) telescope equipped with a dual resolution spectrograph be undertaken. Leadership through the UV " Dark Age " will take the Canadian space astronomy community to new heights of credibility.