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