Extinction Law Object¶
The extinction law can be defined using the classes in spisea/reddening.py. These can be called by:
from spisea import reddening
red_law = reddening.<redlaw_name>()
SPISEA uses the pysynphot framework to define the extinction law. The output is a pysynphot.reddening.CustomRedLaw oject. The reddening law is reported in terms of A_lambda / A_Ks, and thus is normalized to A_Ks = 1.
The red_law object is passed into the Isochrone Object in order to define the extinction for the stars. See the Quick Start for an example.
Available extinction laws:
RedLawPowerLaw
RedLawBrokenPowerLaw
RedLawRiekeLebofsky
RedLawCardelli
RedLawIndebetouw05
RedLawRomanZuniga07
RedLawFitzpatrick09
RedLawNishiyama09 (default)
RedLawSchoedel10
RedLawFritz11
RedLawDamineli16
RedLawDeMarchi16
RedLawSchlafly16
RedLawHosek18b
RedLawNoguerasLara18
RedLawNoguerasLara20
Extinction Law Classes¶
- class reddening.RedLawPowerLaw(alpha, K_wave, wave_min=0.5, wave_max=5.0)¶
Extinction object that is a power-law extinction law: \(A_{\lambda} \propto \lambda^{lpha}\).
For example, to create an extinction law between 0.8 and 3 microns where \(lpha = 2.21\), where \(A_{\lambda} / A_{Ks} = 1\) at 2.12 microns:
>>> from spisea import reddening >>> red_law = reddening.RedLawPowerLaw(2.21, 2.12, wave_min=0.8, wave_max=3.0)
- Parameters
- alphafloat
Exponent of the extinction power-law.
- K_wavefloat
Extinction law is normalized such that AKs = 1 at K_wave.
- wave_minfloat; optional
Minimum wavelength of the extinction law, in microns. Default is 0.5 microns.
- wave_maxfloat; optional
Maximum wavelength of the extinction law, in microns. Default is 5.0 microns
Methods
powerlaw(wavelength, AKs)Return the extinction at a given wavelength assuming the extinction law and an overall AKs value.
- powerlaw(wavelength, AKs)¶
Return the extinction at a given wavelength assuming the extinction law and an overall AKs value.
- Parameters
- wavelengthfloat or array
Wavelength to return extinction for, in microns
- AKsfloat
Total extinction in AKs, in mags
- class reddening.RedLawBrokenPowerLaw(lambda_limits, alpha_vals, K_wave)¶
Extinction object that is a broken power-law extinction law: \(A_{\lambda} \propto \lambda^{lpha[n]}\)
for: :math: lambda_{limits}[n] < lambda <= lambda_{limits}[n+1]
Note: lambda_limits must be continuous in wavelength and K_wave must be within one of the section defined by the lambda_limits array. Extinction law is only defined over lambda_limits
Units of lambda_limits array is microns.
- Parameters
- lambda_limitsnumpy array
Array of length (N + 1) with lower and upper wavelength limits of the power-law segments. Units are microns.
- alpha_valsnumpy array
Array of length N that contains the powers for each power-law segment.
- K_wavefloat
Extinction law is normalized such that AKs = 1 at K_wave.
Methods
broken_powerlaw(wavelength, AKs)Return the extinction at a given wavelength assuming the extinction law and an overall AKs value.
- broken_powerlaw(wavelength, AKs)¶
Return the extinction at a given wavelength assuming the extinction law and an overall AKs value.
- Parameters
- wavelengthfloat or array
Wavelength to return extinction for, in microns
- AKsfloat
Total extinction in AKs, in mags
- class reddening.RedLawRiekeLebofsky¶
Defines the extinction law from Rieke & Lebofsky 1985 for the Galactic Center. The law is defined between 1.0 - 5.0 microns.
A_lambda / A_Ks = 1 when lambda = 2.2 microns
Methods
RiekeLebofsky85(wavelength, AKs)Return the extinction at a given wavelength assuming the extinction law and an overall AKs value.
- RiekeLebofsky85(wavelength, AKs)¶
Return the extinction at a given wavelength assuming the extinction law and an overall AKs value.
- Parameters
- wavelengthfloat or array
Wavelength to return extinction for, in microns
- AKsfloat
Total extinction in AKs, in mags
- class reddening.RedLawCardelli(Rv)¶
Defines the extinction law from Cardelli et al. 1989. The law is defined from 0.3 - 3 microns, and in terms of \(A_{\lambda} / A_{Ks}\), where Ks is 2.174 microns.
- Parameters
- Rvfloat
Ratio of absolute to selective extinction, \(A(V) / E(B-V)\). The standard value for the diffuse ISM is 3.1.
Methods
Cardelli89(wavelength, AKs)Return the extinction at a given wavelength assuming the extinction law and an overall AKs value.
- Cardelli89(wavelength, AKs)¶
Return the extinction at a given wavelength assuming the extinction law and an overall AKs value.
- Parameters
- wavelengthfloat or array
Wavelength to return extinction for, in microns
- AKsfloat
Total extinction in AKs, in mags
- class reddening.RedLawIndebetouw05¶
Defines the extinction law from Indebetouw et al. 2005. The law is defined between 1.25 - 8 microns using Equation 4 in their paper.
Note that A_lambda / A_K = 1 when lambda = 2.164 microns.
Methods
Indebetouw05(wavelength, AK)Return the extinction at a given wavelength assuming the extinction law and an overall extinction at AK (2.164 microns)
- Indebetouw05(wavelength, AK)¶
Return the extinction at a given wavelength assuming the extinction law and an overall extinction at AK (2.164 microns)
- Parameters
- wavelengthfloat or array
Wavelength to return extinction for, in microns
- AKsfloat
Total extinction in AKs, in mags
- class reddening.RedLawRomanZuniga07¶
Defines extinction law from Roman-Zuniga et al. 2007 for the dense cloud core Barnard 59. The law is a cubic spline fit to the values of A_lambda / A_Ks derived using the color-color diagrams slopes in their Table 1. It is defined between 1.0 - 8.0 microns.
A_lambda / A_Ks = 1 when lambda = 2.164 microns
Methods
RomanZuniga07(wavelength, AKs)Return the extinction at a given wavelength assuming the extinction law and an overall AKs value.
- RomanZuniga07(wavelength, AKs)¶
Return the extinction at a given wavelength assuming the extinction law and an overall AKs value.
- Parameters
- wavelengthfloat or array
Wavelength to return extinction for, in microns
- AKsfloat
Total extinction in AKs, in mags
- class reddening.RedLawFitzpatrick09(alpha, RV)¶
Defines the extinction law from Fitzpatrick et al. 2009. The law is defined between 0.5 – 3 microns.
The extinction law is as defined in their equation 5, and has two free parameters: \(lpha\) and R(V). Averaged over 14 sight-lines, the authors generally find either \(alpha\) ~ 2.5, R(V) ~ 3, or \(alpha\) ~ 1.8, R(V) ~ 5 (their Figure 6).
A_lambda / A_K = 1 at lambda = 2.18
- Parameters
- alphafloat
alpha parameter for extinction law.
- RVfloat
R(V) parameter for extinction law.
Methods
Fitzpatrick09(wavelength, AKs)Return the extinction at a given wavelength assuming the extinction law and an overall AKs value.
- Fitzpatrick09(wavelength, AKs)¶
Return the extinction at a given wavelength assuming the extinction law and an overall AKs value.
- Parameters
- wavelengthfloat or array
Wavelength to return extinction for, in microns
- AKsfloat
Total extinction in AKs, in mags
- class reddening.RedLawNishiyama09¶
The extinction law towards the Galactic Center from Nishiyama et al. 2009, combined with the Av / AKs value from Nishiyama et al. 2008. This law is defined between 0.5 - 8.0 microns.
This law is constructed in 3 segments:
0.5 – 1.24 microns: a linear interpolation in log(1/lambda) vs log(A/AKs) space between the Av/AKs and AJ/AKs values
1.25 – 2.14 microns: a power law with index of 2.0
2.14 – 8.0 microns: a spline interpolation between the observed extinction values
A_lambda / A_Ks = 1 when lambda = 2.14 microns
This is the default extinction law.
Methods
Nishiyama09(wavelength, AKs)Return the extinction at a given wavelength assuming the extinction law and an overall AKs value.
- Nishiyama09(wavelength, AKs)¶
Return the extinction at a given wavelength assuming the extinction law and an overall AKs value.
- Parameters
- wavelengthfloat or array
Wavelength to return extinction for, in microns
- AKsfloat
Total extinction in AKs, in mags
- class reddening.RedLawSchoedel10¶
Defines extinction law from Schoedel et al. 2010 for the Galactic Center. It is defined between 1.5 - 3.8 microns.
Power law indices:
1.677 - 2.168 microns —> alpha = 2.21 +/- 0.24
2.168 - 3.636 microns —> alpha = 1.34 +/- 0.29
Wavelengths come from effective wavelengths of observations (some buffer is added to either side of these values).
Reddening law is scaled such that A_lambda / A_Ks = 1 at lambda = 2.168 microns.
Methods
Schoedel10(wavelength, AKs)Return the extinction at a given wavelength assuming the extinction law and a total extinction at scale_lambda (the wavelength where the extinction law = 1)
- Schoedel10(wavelength, AKs)¶
Return the extinction at a given wavelength assuming the extinction law and a total extinction at scale_lambda (the wavelength where the extinction law = 1)
- Parameters
- wavelengthfloat or array
Wavelength to return extinction for, in microns
- AKsfloat
Total extinction at scale_lambda, in mags
- class reddening.RedLawFritz11(scale_lambda=2.166)¶
Defines extinction law from Fritz et al. 2011 for the Galactic Center. The law is defined from 1.0 – 26 microns.
By default, law is scaled such that A_lambda / A_2.166 microns = 1. According to Fritz+11, A_2.166 microns = 2.62 +/- 0.11 mag is the total extinction towards the inner 14”x20” of the MW.
Methods
Fritz11(wavelength, A_scale_lambda)Return the extinction at a given wavelength assuming the extinction law and a total extinction at the scale_lambda (the wavelength where the extinction law = 1)
- Fritz11(wavelength, A_scale_lambda)¶
Return the extinction at a given wavelength assuming the extinction law and a total extinction at the scale_lambda (the wavelength where the extinction law = 1)
- Parameters
- wavelengthfloat or array
Wavelength to return extinction for, in microns
- A_scale_lambdafloat
Total extinction at scale_lambda, in mags
- class reddening.RedLawDamineli16¶
Defines the extinction law of Damineli et al. 2016, derived for the Wd1 cluster. The law is derived between 0.4 - 4.8 microns.
Law is scaled such that A_lambda / A_Ks = 1 at 2.156 microns
Methods
Damineli16(wavelength, AKs)Return the extinction at a given wavelength assuming the extinction law and an overall AKs value.
- Damineli16(wavelength, AKs)¶
Return the extinction at a given wavelength assuming the extinction law and an overall AKs value.
- Parameters
- wavelengthfloat or array
Wavelength to return extinction for, in microns
- AKsfloat
Total extinction in AKs, in mags
- class reddening.RedLawDeMarchi16¶
Defines extinction law from De Marchi et al. 2016 derived for 30 Dorodus. The law is defined between 0.3 - 8.0 microns.
Methods
DeMarchi16(wavelength, AK)Return the extinction at a given wavelength assuming the extinction law and an overall AKs value.
- DeMarchi16(wavelength, AK)¶
Return the extinction at a given wavelength assuming the extinction law and an overall AKs value.
- Parameters
- wavelengthfloat or array
Wavelength to return extinction for, in microns
- AKsfloat
Total extinction in AKs, in mags
- class reddening.RedLawSchlafly16(AH_AKs, x)¶
Defines the extinction law from Schlafly et al. 2016. The law is defined between 0.5 - 4.8 microns.
The law is scaled such that A_lambda / A_Ks = 1 when lambda = 2.151
- Parameters
- AH_AKsfloat
Ratio of A_H / A_Ks, which sets the normalization of the law (see Schlafly+16)
- xfloat
Free parameter in extinction law (see Schlafly+16, Eqn 6)
Methods
Schlafly16(wavelength, AKs)Return the extinction at a given wavelength assuming the extinction law and an overall AKs value.
- Schlafly16(wavelength, AKs)¶
Return the extinction at a given wavelength assuming the extinction law and an overall AKs value.
- Parameters
- wavelengthfloat or array
Wavelength to return extinction for, in microns
- AKsfloat
Total extinction in AKs, in mags
- class reddening.RedLawHosek18b¶
Defines extinction law from Hosek et al. 2019 for the Arches cluster and Wd1. The law is derived between 0.7 - 3.54 microns
Methods
Hosek18b(wavelength, AKs)Return the extinction at a given wavelength assuming the extinction law and an overall AKs value.
- Hosek18b(wavelength, AKs)¶
Return the extinction at a given wavelength assuming the extinction law and an overall AKs value.
- Parameters
- wavelengthfloat or array
Wavelength to return extinction for, in microns
- AKsfloat
Total extinction in AKs, in mags
- class reddening.RedLawNoguerasLara18¶
Defines extinction law from Nogueras-Lara et al. 2018 for the Galactic Center. It is defined between 1.0 - 3.0 microns. Measurements were made in JHK, with effective wavelengths of 1.2685, 1.6506, and 2.1629 microns, respectively.
This extinction law is a single power law with exponent of alpha = 2.3 +/- 0.08.
Reddening law is scaled such that A_lambda / A_Ks = 1 at lambda = 2.163 microns (the observed K-band)
Methods
NoguerasLara18(wavelength, AKs)Return the extinction at a given wavelength assuming the extinction law and an overall AKs value.
- NoguerasLara18(wavelength, AKs)¶
Return the extinction at a given wavelength assuming the extinction law and an overall AKs value.
- Parameters
- wavelengthfloat or array
Wavelength to return extinction for, in microns
- AKsfloat
Total extinction in AKs, in mags
- class reddening.RedLawNoguerasLara20¶
Defines extinction law from Nogueras-Lara et al. 2020 for the Galactic Center. It is defined between 1.0 – 3 microns. Measurements were made in JHK, with effective wavelengths of 1.2685, 1.6506, and 2.1629 microns, respectively
Measured power law indices:
1.2685 - 1.6505 microns —> alpha = 2.44 +/- 0.05
1.6505 - 2.1629 microns —> alpha = 2.23 +/- 0.05
Wavelengths come from effective wavelengths of observations (some buffer is added to either side of these values).
Reddening law is scaled such that A_lambda / A_Ks = 1 at lambda = 2.163 microns (the observed K-band)
Methods
NoguerasLara20(wavelength, AKs)Return the extinction at a given wavelength assuming the extinction law and a total extinction at scale_lambda (the wavelength where the extinction law = 1)
- NoguerasLara20(wavelength, AKs)¶
Return the extinction at a given wavelength assuming the extinction law and a total extinction at scale_lambda (the wavelength where the extinction law = 1)
- Parameters
- wavelengthfloat or array
Wavelength to return extinction for, in microns
- AKsfloat
Total extinction at scale_lambda, in mags