Ultraviolet Background Radiation

Previous abstract Next abstract

Session 14 -- Interstellar Dust and Extinction
Display presentation, Wednesday, January 12, 9:30-6:45, Salons I/II Room (Crystal Gateway)

[14.09] Ultraviolet Background Radiation

R.C.Henry, J.Murthy (JHU)

The UVX experiment was carried on the Space Shuttle Columbia between 1986 January 12 and 19 (STS-61C). Several ultraviolet spectrometers were used to obtain measurements of the diffuse ultraviolet background at 8 locations in the sky. We have reanalysed the UVX measurements of the surface brightness of the diffuse ultraviolet background above b = 40 using the dust-scattering model of Onaka \& Kodaira (1991), which explicitly takes into account the variation of the source function with galactic longitude. The range of allowed values of interstellar grain albedoJa, and scattering asymmetry parameter g, is considerably expanded over those of a previous analysis. The new chi square probability contours come close to, but do not include, the values of a and g found for the interstellar grains by Witt et al. (1992) using the Ultraviolet Imaging Telescope (UIT) on the Astro mission. If we hypothesize in additon to the dust-scattered light an extragalactic component, of 300 1 100 photons cm-2 s-1 sr-1 A-1, attenuated by a cosecant b law, the new reduction of the UVX data gives complete consistency with the Witt et al. determination of the optical parameters of the grains in the ultraviolet.

This work was supported by United States Air Force Contract F19628-93-K-0004, and by National Aeronautics and Space Administration grant NASA NAG5-619. We are grateful for the encouragement of Dr. Stephan Price, and we thank Dr. L. Danly for information.

Onaka, T., \& Kodaira, K. 1991, ApJ, 379, 532

Witt, A. N., Petersohn, J. K., Bohlin, R. C., O'Connell, R. W., Roberts, M. S., Smith, A. M., \& Stecher, T. P. 1992, ApJ, 395, L5

Wednesday program listing