The width of echelle orders in IUE images as derived with the astronomical image display and analysis /AIDA/ system in Tuebingen

Abstract

This paper describes the image display and analysis facilities developed at the Astronomical Institute in Tübingen. The software governing the system is highly modular and allows easy addition of further routines. With this system we have determined the width of the echelle orders in International Ultraviolet Explorer geometrically and photometrically corrected images. This information is essential for a proper treatment of the background in spectra derived from such images.

In the AIDA system high dispersion images are reduced using a gauss-fit to three adjacent orders for determination of the local background in the echelle image, followed by spectral extraction using a slit-height of only 2 times the Gauss width. This limited extraction slit excludes the unwanted order overlap as well as most of the disturbing reseaux and hot pixels of IUE images.