What is nfw?

NFW typically refers to the Navarro-Frenk-White profile, which is a mathematical model that describes the distribution of dark matter in the halos surrounding galaxies. This model was proposed by Julio Navarro, Carlos Frenk, and Simon White in the mid-1990s. The NFW profile is widely used in astrophysics and cosmology to understand the structure and behavior of dark matter halos.

The profile is characterized by a specific density function that decreases with distance from the center of the halo. It has the formula:

[ \rho(r) = \frac{\rho_0}{(r/r_s)(1 + r/r_s)^2} ]

where:

• (\rho(r)) is the density of dark matter at a distance (r) from the center of the halo,
• (\rho_0) is a characteristic density,
• (r_s) is a scale radius at which the profile transitions from a steep slope close to the center to a shallower slope further out.

One of the key features of the NFW profile is that it predicts a "cusp" or an increase in density toward the center of the halo, a point of debate and research since observations sometimes favor a "core" of constant density in the central region. This discrepancy between the theoretical NFW profile and observed dark matter distributions, known as the "core-cusp problem," remains an active area of research in cosmology.

The NFW profile has been instrumental in improving our theoretical understanding of halo formation and the role of dark matter in the universe. It has been supported by numerous N-body simulations of structure formation in a universe dominated by cold dark matter.