Abstract
The surface distribution of dark clouds along the major and minor axes were compiled to give a general formula expressing the surface distribution along both axes simultaneously. Absorption values were determined, assuming the parameters of the standard cloud model as a function of the distance from the two-dimensional distribution of dark clouds. Iso-cloud line numbers were drawn as a function of bothX andY. Two knots appeared in the new distribution function. This may announce the beign of the spiral arms. The knots may indicate the least possible number of the dark clouds per kiloparsec beyond which spiral structure may be possible. The projected distance of the two knots on the X-axis may correspond to some spiral features found by other investigators.
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Issa, I.A. Archimedes spiral and the surface distribution of dark clouds in M31, III. Astrophys Space Sci 184, 227–234 (1991). https://doi.org/10.1007/BF00642971
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DOI: https://doi.org/10.1007/BF00642971