A TEST FOR HIGH LATITUDE ABSORPTION AS A FACTOR IN THE DISTRIBUTION OF GALAXIES

Abstract

In our investigations of the distribution of galaxies we find, as is well known, a conspicuous unevenness in latitudes below ±30°, which is largely attributable to dust clouds in our own galaxy. In these low latitudes the presence of effective absorption is generally shown also in the distribution of stars. For example, the absorption is faintly shown in the distribution of the stars as well as of the galaxies around the north celestial pole,1 but more emphatically in the rift of the Milky Way where both galaxies and distant stars are completely blotted out. The question arises whether or not the unevenness in the distribution of high latitude galaxies is also due to clouds of absorbing material, either near the galactic plane or farther out, possibly in the intergalactic regions. And if it is caused by uneven intervening light absorption, will the high latitude galactic stars also show an analogous uneven distribution ? They should if the absorption is near the galactic plane ; and sufficiently dense intergalactic absorption seems very unlikely. A test for the possible correlation of nebular with stellar distribution is provided in Table I and in Figures 1 and 2 for eight fields m the North Galactic Cap. For each long exposure plate made with the Bruce (A) or the Metcalf (MC) doublet we have established stellar magnitude sequences based on the Seares and van Rhijn tables. Residual errors in these magnitude standards are irrelevant in the comparison of neighboring fields. On each plate the numbers of stars and galaxies were counted in two contrasting square degrees, one very rich and one relatively poor in number of galaxies. The square degrees chosen on each plate are adjacent; on one A plate two pairs were counted. Only areas close enough to the plate centers to be free of appreciable distance correction were used. The star counts by Mr. Forbes (F) include for each pair all stars brighter than a selected faint magnitude that was alike for rich and poor fields but usually different from the