__author__ = 'sibirrer'
#this file contains a class to make a gaussian
import numpy as np
import lenstronomy.Util.util as util
from lenstronomy.LensModel.Profiles.sersic_utils import SersicUtil
from lenstronomy.LensModel.Profiles.base_profile import LensProfileBase
__all__ = ['Sersic']
[docs]class Sersic(SersicUtil, LensProfileBase):
"""
this class contains functions to evaluate a Sersic mass profile: https://arxiv.org/pdf/astro-ph/0311559.pdf
"""
param_names = ['k_eff', 'R_sersic', 'n_sersic', 'center_x', 'center_y']
lower_limit_default = {'k_eff': 0, 'R_sersic': 0, 'n_sersic': 0.5, 'center_x': -100, 'center_y': -100}
upper_limit_default = {'k_eff': 10, 'R_sersic': 100, 'n_sersic': 8, 'center_x': 100, 'center_y': 100}
[docs] def function(self, x, y, n_sersic, R_sersic, k_eff, center_x=0, center_y=0):
"""
:param x: x-coordinate
:param y: y-coordinate
:param n_sersic: Sersic index
:param R_sersic: half light radius
:param k_eff: convergence at half light radius
:param center_x: x-center
:param center_y: y-center
:return:
"""
n = n_sersic
x_red = self._x_reduced(x, y, n, R_sersic, center_x, center_y)
b = self.b_n(n)
#hyper2f2_b = util.hyper2F2_array(2*n, 2*n, 1+2*n, 1+2*n, -b)
hyper2f2_bx = util.hyper2F2_array(2*n, 2*n, 1+2*n, 1+2*n, -b*x_red)
f_eff = np.exp(b) * R_sersic ** 2 / 2. * k_eff# * hyper2f2_b
f_ = f_eff * x_red**(2*n) * hyper2f2_bx# / hyper2f2_b
return f_
[docs] def derivatives(self, x, y, n_sersic, R_sersic, k_eff, center_x=0, center_y=0):
"""
returns df/dx and df/dy of the function
"""
x_ = x - center_x
y_ = y - center_y
r = np.sqrt(x_**2 + y_**2)
if isinstance(r, int) or isinstance(r, float):
r = max(self._s, r)
else:
r[r < self._s] = self._s
alpha = -self.alpha_abs(x, y, n_sersic, R_sersic, k_eff, center_x, center_y)
f_x = alpha * x_ / r
f_y = alpha * y_ / r
return f_x, f_y
[docs] def hessian(self, x, y, n_sersic, R_sersic, k_eff, center_x=0, center_y=0):
"""
returns Hessian matrix of function d^2f/dx^2, d^2/dxdy, d^2/dydx, d^f/dy^2
"""
x_ = x - center_x
y_ = y - center_y
r = np.sqrt(x_**2 + y_**2)
if isinstance(r, int) or isinstance(r, float):
r = max(self._s, r)
else:
r[r < self._s] = self._s
d_alpha_dr = self.d_alpha_dr(x, y, n_sersic, R_sersic, k_eff, center_x, center_y)
alpha = -self.alpha_abs(x, y, n_sersic, R_sersic, k_eff, center_x, center_y)
#f_xx_ = d_alpha_dr * calc_util.d_r_dx(x_, y_) * x_/r + alpha * calc_util.d_x_diffr_dx(x_, y_)
#f_yy_ = d_alpha_dr * calc_util.d_r_dy(x_, y_) * y_/r + alpha * calc_util.d_y_diffr_dy(x_, y_)
#f_xy_ = d_alpha_dr * calc_util.d_r_dy(x_, y_) * x_/r + alpha * calc_util.d_x_diffr_dy(x_, y_)
f_xx = -(d_alpha_dr/r + alpha/r**2) * x_**2/r + alpha/r
f_yy = -(d_alpha_dr/r + alpha/r**2) * y_**2/r + alpha/r
f_xy = -(d_alpha_dr/r + alpha/r**2) * x_*y_/r
return f_xx, f_xy, f_xy, f_yy