Sersic2D

class sherpa.astro.models.Sersic2D(name='sersic2d')

Bases: sherpa.models.model.ArithmeticModel

Two-dimensional Sersic model.

This is a generalization of the DeVaucouleurs2D model, in which the exponent n can vary ([1], [2], and [3]).

r0

The core radius.

xpos

The center of the model on the x0 axis.

ypos

The center of the model on the x1 axis.

ellip

The ellipticity of the model.

theta

The angle of the major axis. It is in radians, measured counter-clockwise from the X0 axis (i.e. the line X1=0).

ampl

The amplitude refers to the maximum peak of the model.

n

The Sersic index (n=4 replicates the DeVaucouleurs2D model).

See also

Beta2D, DeVaucouleurs2D, HubbleReynolds, Lorentz2D

Notes

The functional form of the model for points is can be expressed as the following:

f(x0,x1) = ampl * exp(-b(n) * (r(x0,x1)^(1/n) - 1))

    b(n) = 2 * n - 1 / 3 + 4 / (405 * n) + 46 / (25515 * n^2)

r(x0,x1)^2 = xoff(x0,x1)^2 * (1-ellip)^2 + yoff(x0,x1)^2
             -------------------------------------------
                          r0^2 * (1-ellip)^2

xoff(x0,x1) = (x0 - xpos) * cos(theta) + (x1 - ypos) * sin(theta)

yoff(x0,x1) = (x1 - ypos) * cos(theta) - (x0 - xpos) * sin(theta)

The grid version is evaluated by adaptive multidimensional integration scheme on hypercubes using cubature rules, based on code from HIntLib ([4]) and GSL ([5]).

References

[1]	http://ned.ipac.caltech.edu/level5/March05/Graham/Graham2.html

[2]	Graham, A. & Driver, S., 2005, PASA, 22, 118 http://adsabs.harvard.edu/abs/2005PASA...22..118G

[3]	Ciotti, L. & Bertin, G., A&A, 1999, 352, 447-451 http://adsabs.harvard.edu/abs/1999A%26A...352..447C

[4]	HIntLib - High-dimensional Integration Library http://mint.sbg.ac.at/HIntLib/

[5]	GSL - GNU Scientific Library http://www.gnu.org/software/gsl/

Attributes Summary

thawedparhardmaxes
thawedparhardmins
thawedparmaxes
thawedparmins
thawedpars

Methods Summary

apply(outer, \*otherargs, \*\*otherkwargs)
calc(\*args, \*\*kwargs)
get_center()
guess(dep, \*args, \*\*kwargs)
reset()
set_center(xpos, ypos, \*args, \*\*kwargs)
startup()
teardown()

Attributes Documentation

thawedparhardmaxes

thawedparhardmins

thawedparmaxes

thawedparmins

thawedpars

Methods Documentation

apply(outer, *otherargs, **otherkwargs)

calc(*args, **kwargs)

get_center()

guess(dep, *args, **kwargs)

reset()

set_center(xpos, ypos, *args, **kwargs)

startup()

teardown()