Results from the Ultraviolet Imaging Telescope on the Astro-2 Mission

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Session 16 -- Astro 2
Oral presentation, Monday, June 12, 1995, 2:00pm - 3:30pm

[16.02] Results from the Ultraviolet Imaging Telescope on the Astro-2 Mission

T.P. Stecher (GSFC/LASP), R.C. Bohlin (STScI), S.G. Neff (GSFC/LASP), R.W. O'Connell (UVa), M.R. Roberts (NRAO), A.M. Smith (GSFC/LASP)

The solar-blind UIT camera with a CsI cathode obtained 722 frames with a cumulative exposure time of 260705 seconds during the March 1995 Astro-2 mission of Space Shuttle Endeavour. Filters were used to isolate selected bandpasses in the range 1200-1800\AA, over the 40 arcmin field of view. Spatial resolution on most of the images is about 3 arcsec. Calibrated data, converted to machine-readable form, are under analysis and several posters on these investigations are presented in the Astro-2 poster session at this meeting (a first look at the UIT observations of Omega Cen, M31, and the Cygnus Loop is further elaborated here). UIT imagery of 20 spiral galaxies was obtained as part of a Guest Investigator program (Wendy Freedman \ea). UV imaging suppresses the red stellar population as expected and enhances the appearance of tracers of recent star formation. Known \hii~ regions in these galaxies are made apparent through the scattering of stellar ultraviolet light by interstellar dust; typically their shapes differ from those seen in \ha. A radial color gradient investigation will be delayed until ground observations can be made as the long-wavelength camera failed on launch and only the 1520 \AA~ and 1620 \AA~ images were made. The far-UV (1520\AA) features are detected well beyond the Holmberg radius. UV/visible color-magnitude diagrams will be made as they were for the data from Astro-1. Our deepest images of the Magellanic Clouds reveal a rich field of luminous clusters and stars that are being searched for UV counterparts of the known x-ray sources in the photographed areas. The observed stars in the Clouds will be used to determine the current mass function. The respective contributions of nebular and stellar UV light in reflection nebulae are will be studied as several nebulae were observed with differing geometries and will provide interesting results on the far-UV albedo and phase function of nebular dust. A dozen globular and open clusters were imaged.

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