Department of Physics and Astronomy
Potential-Density Phase-Shift Page of
Dr. Ronald J. Buta, Professor of Astronomy
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The potential-density phase-shift is a useful tool for probing the structure and evolution of galaxies. The idea was developed by Dr. Xiaolei Zhang, currently affiliated with George Mason University, in a series of Astrophysical Journal papers published in the 1990s. Since 2005, Dr. Zhang and I have collaborated on applying her ideas to real galaxies. The papers at right are our most detailed applications so far. Click here to see a figure that summarizes some of our main findings from the two studies.

This schematic (courtesy Dr. X. Zhang) shows the basic idea of the Zhang theory as applied to a spiral galaxy. The density spiral leads the potential spiral inside the corotation resonance radius, rCo, and trails the potential spiral outside rCo. These phase differences cause a galaxywide torquing action that changes sign at corotation and can influence the evolution of the basic state of the galactic disk.

"The Potential-Density Phase-Shift Method for Determining the Corotation Radii in Spiral and Barred Galaxies", by X. Zhang and R. Buta, Astronomical Journal, 133, 2584, 2007

"Corotation Radii from Potential-Density Phase-Shifts for 153 OSUBGS Sample Galaxies," by R. Buta and X. Zhang, Astrophysical Journal Supplement Series, 182, 559, 2009
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