An observational model of the zodiacal light brightness distribution

초록

The zodiacal light (ZL) has been newly derived from photo-polarimetric nightsky observations at Mt. Haleakala, Hawaii on the night of 21/22 August, 1968. The resulting ZL brightness map has spatial resolution 2degrees x 2degrees and covers most of the sky that can be reached from the ground, extending ecliptic longitude over 30degrees less than or equal to Lambda - Lambda(circle dot) less than or equal to 330degrees and latitude -90degrees less than or equal to beta less than or equal to 90degrees. By utilizing a semi-empirical method for correcting the atmospheric diffuse light and an improved technique for making individual star subtraction, we have reduced the relative uncertainty in the ZL brightness from the previous level of similar to20% down to similar to10%, which helps to reveal small scale structures in the observed brightness distribution. Since the primary data base employed in our reduction was restricted to the observations over a single night, the resulting map demonstrates asymmetries in the ZL brightness distribution over the morning and evening sides and also over the northern and southern ecliptic hemispheres. From these asymmetries we were able to locate the plane of maximum density of interplanetary dust particles at inclination i similar or equal to 2degrees and longitude of ascending node Omega similar or equal to 80degrees. To improve and homogenize the sky coverage the primary data base was then supplemented with observations on six additional nights, four in August and two in February of the same year. By folding the ZL brightness in the northern and southern hemispheres and also in the morning and evening sides upon each other, we have constructed an observational model of the ZL brightness in 2degrees intervals of ecliptic coordinates. (C) 2004 Elsevier B.V. All rights reserved.

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