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The origin and maintenance of spiral structure in galaxies, the correlationbetween different types of spiral structure and several proposed mechanisms fortheir generation, and the evolution of spiral arms of galaxies with time arequestions that are still controversial. In this note we study the spiralstructure in a sample of distant galaxies in order to infer the evolution ofspiral arm characteristics with redshift. We considered a sample of 171 face-onspiral galaxies in the Hubble Space Telescope COSMOS (The Cosmic EvolutionSurvey) field. The galaxies are distributed up to $z \approx 1$ with a meanvalue of 0.44. For all galaxies, we determined the pitch angles of the spiralarms and analysed their dependence on redshift; a total of 359 arms weremeasured. Analyses of our measurements combined with the literature datasuggest a possible evolution of the pitch angles of spiral galaxies: by themodern epoch the spiral pattern, on average, becomes more tightly wound. Thismay be a consequence of the general evolution of the structure of galaxies asgalaxies become more massive over time and their bulges grow. In addition, thedistribution of the cotangent of pitch angle of galaxies indicates thepossibility that the dominant mechanism of spiral pattern generation changesover time.

The possible evolution of pitch angles of spiral galaxies