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Python routines for computing Navarro-Frenk-White halo properties

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This class implements the NFW (Navarro, Julio F. Frenk, Carlos S. White, Simon D. M., “A Universal Density Profile from Hierarchical Clustering”, The Astrophysical Journal vol. 490, pp. 493-508, 1997) halo profile. It allows easy computation of halo quantities such as mass at and radius of specified overdensities. Overdensities can be specified either with respect to the critical or mean density of the Universe.

Class instances can be created at different overdensities. As such the class allows for easy conversion between masses and concentration parameters between different mass definitions.

Surface mass density and differential surface mass density methods are available for weak lensing applications.


The easiest way to install the NFW module is to use pip:

$ pip install NFW


This implementation of the NFW halo properties depends on

  • numpy >= 1.9

  • scipy >= 0.16

  • astropy >= 2.0

Older versions may work but are untested. In particular astropy > 1.0 is known to work but the unit tests will fail because astropy-2.0 updated physical constants from CODATA 2010 to CODATA 2014.


Jörg Dietrich


Development takes place on GitHub. Please report any bugs as an issue in the GitHub issue tracker.


NFW is released under an MIT license. See LICENCE.txt

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