Image Details
Caption: Fig. 4.
Area used to measure the mean surface brightness ﹩\overline{\Sigma }﹩ (dark regions) compared to the total disk area for M51 and M101. The area and ﹩\overline{\Sigma }﹩ are used to scale the distribution function in Fig. 3. Left: M51. The fraction of total disk area used is ~35%. Right: M101. The fraction of total disk area used is ~10%.
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