Hubble–Reynolds law

The Hubble–Reynolds law models the surface brightness of elliptical galaxies as

I(R)={\frac {I_{0}}{(1+R/R_{H})^{2}}}

Where $I(R)$ is the surface brightness at radius $R$ , $I_{0}$ is the central brightness, and $R_{H}$ is the radius at which the surface brightness is diminished by a factor of 1/4. It is asymptotically similar to the De Vaucouleurs' law which is a special case of the Sersic profile for elliptical galaxies.[1]

The law is named for the astronomers Edwin Hubble and John Henry Reynolds. It was first formulated by Reynolds in 1913[2] from his observations of galaxies (then still known as nebulae). It was later re-derived by Hubble in 1930[3] specifically in observations of elliptical galaxies.

References

Binney & Tremaine. Galactic Dynamics 2008.
Reynolds, J. H. (12 December 1913). "The Light Curve of the Andromeda Nebula (N.G.C. 224)". Monthly Notices of the Royal Astronomical Society. 74 (2): 132–136. Bibcode:1913MNRAS..74..132R. doi:10.1093/mnras/74.2.132.
Hubble, E. P. (May 1930). "Distribution of luminosity in elliptical nebulae". The Astrophysical Journal. 71: 231. Bibcode:1930ApJ....71..231H. doi:10.1086/143250.

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[1] Binney & Tremaine. Galactic Dynamics 2008.

[2] Reynolds, J. H. (12 December 1913). "The Light Curve of the Andromeda Nebula (N.G.C. 224)". Monthly Notices of the Royal Astronomical Society. 74 (2): 132–136. Bibcode:1913MNRAS..74..132R. doi:10.1093/mnras/74.2.132.

[3] Hubble, E. P. (May 1930). "Distribution of luminosity in elliptical nebulae". The Astrophysical Journal. 71: 231. Bibcode:1930ApJ....71..231H. doi:10.1086/143250.