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P2DFFT is a new parallelized version of 2DFFT, a code that allows the user to isolate and measure the spiral arm pitch angle of galaxies. The user input has been simplified and depending on the number of cores available, P2DFFT runs significantly faster than the older serial version, 2DFFT. Further enhancements include:

  • Allowing direct input of FITS images

  • Optionally outputting inverse Fourier transform FITS images

  • Ability to generate idealized logarithmic spiral test images of a specified size that have 1 to 6 arms with pitch angles of -75 degrees to 75 degrees​​

  • Ability to output Fourier amplitude versus inner radius and pitch angle versus inner radius for each Fourier component (m = 0 to m = 6)

  • Ability to calculate the Fourier amplitude weighted mean pitch angle across m = 1 to m = 6 versus inner radius


If you publish results using P2DFFT, please cite the following papers:

  • Hewitt & Treuthardt 2020,"Comparison of Galaxy Spiral Arm Pitch Angle Measurements Using Manual and Automated Techniques", MNRAS 493: 3854-3865 (2020, MNRAS)

  • Mutlu-Pakdil et al. 2018, "The Illustris Simulation: The Supermassive Black Hole - Galaxy Connection Beyond the Bulge", MNRAS 474: 2594-2606 (2018, MNRAS)

  • Davis et al. 2012, "Measurement of Galactic Logarithmic Spiral Arm Pitch Angle Using Two-Dimensional Fast Fourier Transform Decomposition", ApJS 199: 33 (2012, ApJS)

2DFFT can be found here. It is strongly recommended that you use the P2DFFT version because it runs faster and allows for direct input of FITS images.  However, if you decide to publish results using the old 2DFFT code, please you only need cite the Davis et al. (2012) paper.​


Available Versions

Current and previous versions of P2DFFT can be found at

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