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Inverse Relations between 0.25 keV counts and local interstellar dust

Published online by Cambridge University Press:  12 April 2016

J. Knude
Affiliation:
Copenhagen University Observatory
P. Jakobsen
Affiliation:
Copenhagen University Observatory
S. Labov
Affiliation:
Copenhagen University Observatory
S. Bowyer
Affiliation:
Copenhagen University Observatory

Extract

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A preliminary comparison of color excesses and HEA0-1, A2 0.25 keV counts have been performed on two angular levels in order to search for indications of local photoelectric absorption.

a. Color excesses and background counts are smoothed to a common 1.5 1.5 sq.deg. beam. Although distance information on the color excesses are available it is not used in this first attempt. The lines of sight to which the excesses pertain have however a length comparable to the expected viewing distance at these energies in the local medium. Figure 1 displays the resulting average counts/pixel versus average excess/pixel for the five areas investigated. A general decrease of the counts with excess is apparent. The wide scatter in the individual regions is probably due to excess variations on scales smaller than the collimated beam. The minimum counts on the diagram come from a region where an almost coherent sheet of dust is present within a distance ~200 pc. The constancy of the minimum counts in this particular direction indicates that the soft X-ray emission probably originate exclusively in front of the matter observed to be present. Note that the SGP counts show a shallow inverse dependence on excess. The latitude distribution of the five areas assures that the general inverse relation of the 0.25 keV counts on color excesses is not a latitude effect.

Type
Hot Gas in the LISM: Soft X-Ray Observations
Copyright
Copyright © NASA 1984