Significant new method developed for characterizing density wave features

Processed near-infrared images of NGC 4321 generated by Dr. Xiaolei Zhang of the Naval Research Laboratory and Dr. Ronald J. Buta of the University of Alabama. The original image of this galaxy, from which the processed images were derived, came from the SINGS survey of nearby galaxies, obtained using the Infrared Array Camera on board the Spitzer Space Telescope. The acronym NGC refers to the New General Catalogue of Nebulae and Clusters of Stars, compiled at the end of the nineteenth century by Danish astronomer Johan L. E. Dreyer. Top Left: Bar-separated image of the bright inner region of NGC 4321, superimposed with the four corotation circles determined using the phase shift method. Top Right: Spiral-separated image of NGC 4321 of the same region, pictured left, superimposed with the same four corotation circles. Bottom Left: Image (without bar-spiral separation) of NGC 4321 with a factor of two linear zoom, compared to the top panels. Superimposed with the central three corotation circles determined using the phase shift method. Bottom Right: Image (without bar-spiral separation) of NGC 4321 with a factor of four linear zoom, compared to the top panels. Superimposed with the central two corotation circles determined using the phase shift method. Credit: Dr. Xiaolei Zhang, Naval Research Laboratory Dr. Ronald J. Buta, University of Alabama