FM90

class dust_extinction.shapes.FM90(C1=0.1, C2=0.7, C3=3.23, C4=0.41, xo=4.6, gamma=0.99, **kwargs)

Bases: astropy.modeling.Fittable1DModel

Fitzpatrick & Massa (1990) 6 parameter ultraviolet shape model

Parameters

C1: float

y-intercept of linear term

C2: float

slope of liner term

C3: float

amplitude of “2175 A” bump

C4: float

amplitude of FUV rise

xo: float

centroid of “2175 A” bump

gamma: float

width of “2175 A” bump

Notes

From Fitzpatrick & Massa (1990, ApJS, 72, 163)

Only applicable at UV wavelengths

Example showing a FM90 curve with components identified.

import numpy as np
import matplotlib.pyplot as plt
import astropy.units as u

from dust_extinction.shapes import FM90

fig, ax = plt.subplots()

# generate the curves and plot them
x = np.arange(3.8,8.6,0.1)/u.micron

ext_model = FM90()
ax.plot(x,ext_model(x),label='total')

ext_model = FM90(C3=0.0, C4=0.0)
ax.plot(x,ext_model(x),label='linear term')

ext_model = FM90(C1=0.0, C2=0.0, C4=0.0)
ax.plot(x,ext_model(x),label='bump term')

ext_model = FM90(C1=0.0, C2=0.0, C3=0.0)
ax.plot(x,ext_model(x),label='FUV rise term')

ax.set_xlabel(r'$x$ [$\mu m^{-1}$]')
ax.set_ylabel(r'$E(\lambda - V)/E(B - V)$')

ax.legend(loc='best')
plt.show()

(Source code, png, hires.png, pdf)

Attributes Summary

C1
C2
C3
C4
gamma
n_inputs
n_outputs
param_names
x_range
xo

Methods Summary

__call__(self, *inputs[, model_set_axis, …])	Evaluate this model using the given input(s) and the parameter values that were specified when the model was instantiated.
evaluate(in_x, C1, C2, C3, C4, xo, gamma)	FM90 function
fit_deriv(in_x, C1, C2, C3, C4, xo, gamma)	Derivatives of the FM90 function with respect to the parameters

Attributes Documentation

C1 = Parameter('C1', value=0.1)

C2 = Parameter('C2', value=0.7)

C3 = Parameter('C3', value=3.23)

C4 = Parameter('C4', value=0.41)

gamma = Parameter('gamma', value=0.99, bounds=(0.0, None))

n_inputs = 1

n_outputs = 1

param_names = ('C1', 'C2', 'C3', 'C4', 'xo', 'gamma')

x_range = [3.125, 10.964912280701753]

xo = Parameter('xo', value=4.6, bounds=(0.0, None))

Methods Documentation

__call__(self, *inputs, model_set_axis=None, with_bounding_box=False, fill_value=nan, equivalencies=None, inputs_map=None, **new_inputs)

Evaluate this model using the given input(s) and the parameter values that were specified when the model was instantiated.

static evaluate(in_x, C1, C2, C3, C4, xo, gamma)

FM90 function

Parameters

in_x: float

expects either x in units of wavelengths or frequency or assumes wavelengths in wavenumbers [1/micron]

internally wavenumbers are used

Returns

exvebv: np array (float)

E(x-V)/E(B-V) extinction curve [mag]

Raises

ValueError

Input x values outside of defined range

static fit_deriv(in_x, C1, C2, C3, C4, xo, gamma)

Derivatives of the FM90 function with respect to the parameters