effective radius
(Re, half-light radius, galaxy effective radius)
(radius of a galaxy within which 1/2 the light is emitted)
Effective radius (aka half-light radius)
is a measure of the size of a galaxy
that accommodates the fact that while galaxies
grow thinner (fewer stars, less gas) with distance
from the center, they don't have well-defined edges.
The effective radius is defined to be the radius within
which 1/2 the galaxy's light is emitted.
An alternative galaxy size measure is the Holmberg radius.
(galaxies,measure)
Further reading:
https://en.wikipedia.org/wiki/Galaxy_effective_radius
https://astronomy.swin.edu.au/cosmos/e/Effective+Radius
http://spiff.rit.edu/classes/phys443/lectures/gal_1/petro/petro.html
https://www.tng-project.org/data/forum/topic/699/half-light-radii/
Referenced by pages:
fundamental plane
Holmberg radius (RH)
Kormendy relation (KR)
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