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Paper: Amplitudes of Spiral Perturbations
Volume: 480, Structure and Dynamics of Disk Galaxies
Page: 117
Authors: Grosbol, P.; Patsis, P. A.
Abstract: It has proven very difficult to estimate the amplitudes of spiral perturbations in disk galaxies from observations due to the variation of mass-to-light ratio and extinction across spiral arms. Deep, near-infrared images of grand-design spiral galaxies obtained with HAWK-I/VLT were used to analyze the azimuthal amplitude and shape of arms, which, even in the K-band may, be significantly biased by the presence of young stellar populations. Several techniques were applied to evaluate the relative importance of young stars across the arms, such as surface brightness of the disk with light from clusters subtracted, number density of clusters detected, and texture of the disk. The modulation of the texture measurement, which correlates with the number density of faint clusters, yields amplitudes of the spiral perturbation in the range 0.1–0.2. This estimate gives a better estimate of the mass perturbation in the spiral arms, since it is dominated by old clusters.
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