RUI: Completion of the Wide-Angle H-alpha Survey of the Southern Sky

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This award is for the support of a wide-angle imaging survey of the Southern sky at 656.3 nm wavelength, the wavelength of the H-Alpha emission line of hydrogen. This project was begun in 1997 and this award provides support to complete the project. Each image of the survey covers an area of the sky 12.6 minutes of angle in diameter at an angular resolution of about one arcminute, and reaches a sensitivity level of one Rayleigh (6 x 10- 18 erg CM-2 s- I arcsec-2). This corresponds to an emission measure of 2 cm-6 pc, and to a brightness temperature for microwave free-free emission of 6 microKelvin at 30 GHz. The survey uses a CCD detector, a commercial camera lens, and narrow-band interference filters. This instrumentation is mounted on a robotic telescope platform located at Cerro Tololo Inter-American Observatory in Chile. As of October 1998, the survey was about 60% complete, and it is expected to finish the survey in 1999. The survey will provide accurate measurement of anisotropies in the Galactic free-free emission at microwave wavelengths (or proof that these are negligible). This observed emission must be subtracted from satellite or ground-based measurements to obtain the true cosmic microwave background fluctuations. The analysis of the data from the survey will produce detailed information on the structure of the diffuse, warm, ionized component of the interstellar medium. This information is necessary for understanding the dynamics of the interstellar gas. The images will be made available to the astronomical community as an H-Alpha Atlas of the Southern Sky, which will be distributed on CD-ROM disks and made available on the World Wide Web. Participation by several undergraduate students in the project will enhance their understanding of the nature of scientific research.