kron: Kron Function

In astro: Astronomy Functions, Tools and Routines

Description

Calculates Kron parameters based on input Sersic parameters.

Usage

kron(mag, n, e = 0, rk = 2.5, r=1e10, re = 1)

Arguments

mag	total magnitude
n	Sersic index
e	ellipticity (1 - b/a)
rk	integrate out to this many multiples of the Kron radius
r	radius at which to evaluate the Kron radius
re	half-light radius

Details

The Kron radius is defined as the first moment of the surface brightness light profile. Kron (1980) argued that apertures of multiple values of the Kron radius, Rk (typically, Rk = 2 or Rk = 2.5) would contain a sufficient amount of the total flux of the galaxy to be a useful measure of total flux. This is only true if one is able to evaluate the Kron radius at very large radii away from the galaxy centre (using very deep imaging data). If this is not possible (which typically it is not) the Kron radius will be an underestimate, and consequently, so will the Kron magnitude. This problem becomes most acute for those galaxies with high Sersic indices found within shallow imaging data.

Value

mag	magnitude within r
magdiff	difference between total magnitude and magnitude within r
mu	surface brightness at r
muavg	average surface brightness within r
inten	intensity at r
lum	luminosity within r
lumtot	total luminosity
lumfrac	fraction of total luminosity contained within r

Author(s)

Lee Kelvin, <[e-mail]>

References

Graham A. W., Driver S. P., 2005, PASA, 22, 118

See Also

The astronomy package: astro.

astro documentation built on May 2, 2019, 2:14 a.m.