Source code for lenstronomy.LightModel.Profiles.moffat

__author__ = "sibirrer"

# this file contains a class to make a Moffat profile

__all__ = ["Moffat"]


class Moffat(object):
    """This class contains functions to evaluate a Moffat surface brightness profile.

    .. math::

        I(r) = I_0 * (1 + (r/\\alpha)^2)^{-\\beta}

    with :math:`I_0 = amp`.
    """

    def __init__(self):
        self.param_names = ["amp", "alpha", "beta", "center_x", "center_y"]
        self.lower_limit_default = {
            "amp": 0,
            "alpha": 0,
            "beta": 0,
            "center_x": -100,
            "center_y": -100,
        }
        self.upper_limit_default = {
            "amp": 100,
            "alpha": 10,
            "beta": 10,
            "center_x": 100,
            "center_y": 100,
        }

    def function(self, x, y, amp, alpha, beta, center_x=0, center_y=0):
        """2D Moffat profile.

        :param x: x-position (angle)
        :param y: y-position (angle)
        :param amp: normalization
        :param alpha: scale
        :param beta: exponent
        :param center_x: x-center
        :param center_y: y-center
        :return: surface brightness
        """

        x_shift = x - center_x
        y_shift = y - center_y
        return amp * (1.0 + (x_shift**2 + y_shift**2) / alpha**2) ** (-beta)