petro: Petrosian Function

In astro: Astronomy Functions, Tools and Routines

Description

Calculates Petrosian parameters based on input Sersic parameters.

Usage

petro(mag, n, e = 0, rp = 3, i = 0.5)

Arguments

mag	total magnitude
n	Sersic index
e	ellipticity (1 - b/a)
rp	integrate out to this many multiples of the Petrosian radius
i	use this value of 1/petrosian index

Details

The Petrosian function describes the ratio between the average intensity within some projected radius and the intensity at that radius. The value of this ratio is known as the Petrosian index. Typically, a fixed value of 1/Petrosian index, i (usually i = 0.2 or i = 0.5) is chosen in order to define the Petrosian radius. The Petrosian magnitude is then defined as the magnitude lying within a given multiple of the Petrosian radius, Rp (typically, Rp = 2 or Rp = 3 for i = 0.2 and i = 0.5, respectively).

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.