Dered¶
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class
sherpa.astro.models.
Dered
(name='dered')[source] [edit on github]¶ Bases:
sherpa.models.model.RegriddableModel1D
A de-reddening model.
De-reddening model applied multiplicatively to a spectrum. The integrate flag of this model should be set to False when used with an integrated grid.
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rv
¶ The ratio of total to selective extinction.
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nhgal
¶ The absorbing column density of H_gal in units of 10^20 cm^-2.
Notes
This dereddening model uses the analytic formula for the mean extension law described in [1]:
A(lambda) = E(B-V) * (a * rv + b) = 1.086 tau(lambda)
where tau(lambda) is the wavelength-dependent optical depth:
I(lambda) = I(0) * exp(-tau(lambda))
and a and b are computed using wavelength-dependent formulae, which are not reproduced here, for the wavelength range 1000 Angstroms to 3.3 microns. The relationship between the color excess and the column density (nhgal) is [2]:
E(B-V) = nhgal / 58.0
where the units of nhgal is 10^20 cm^-2. The value of the ratio of total to selective extinction, rv, is initially set to 3.1, the standard value for the diffuse ISM. The final model form is:
I(lambda) = I(0) exp(-nhgal * (a * ev + b) / (58.0 * 1.086)
This model provided courtesy of Karl Forster.
References
[1] Cardelli, Clayton, & Mathis 1989, ApJ 345, 245 http://adsabs.harvard.edu/abs/1989ApJ…345..245C [2] Bohlin, Savage, & Drake 1978, ApJ 224, 132 http://adsabs.harvard.edu/abs/1978ApJ…224..132B Attributes Summary
thawedparhardmaxes
thawedparhardmins
thawedparmaxes
thawedparmins
thawedpars
Methods Summary
apply
(outer, *otherargs, **otherkwargs)calc
(pars, xlo, *args, **kwargs)get_center
()guess
(dep, *args, **kwargs)Set an initial guess for the parameter values. regrid
(*arrays, **kwargs)The class RegriddableModel1D allows the user to evaluate in the requested space then interpolate onto the data space. reset
()set_center
(*args, **kwargs)startup
(cache)Called before a model may be evaluated multiple times. teardown
()Called after a model may be evaluated multiple times. Attributes Documentation
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thawedparhardmaxes
¶
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thawedparhardmins
¶
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thawedparmaxes
¶
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thawedparmins
¶
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thawedpars
¶
Methods Documentation
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apply
(outer, *otherargs, **otherkwargs) [edit on github]¶
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calc
(pars, xlo, *args, **kwargs) [edit on github]¶
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get_center
() [edit on github]¶
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guess
(dep, *args, **kwargs) [edit on github]¶ Set an initial guess for the parameter values.
Attempt to set the parameter values, and ranges, for the model to match the data values. This is intended as a rough guess, so it is expected that the model is only evaluated a small number of times, if at all.
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regrid
(*arrays, **kwargs) [edit on github]¶ The class RegriddableModel1D allows the user to evaluate in the requested space then interpolate onto the data space. An optional argument ‘interp’ enables the user to change the interpolation method.
Examples
>>> import numpy as np >>> from sherpa.models.basic import Box1D >>> mybox = Box1D() >>> request_space = np.arange(1, 10, 0.1) >>> regrid_model = mybox.regrid(request_space, interp=linear_interp)
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reset
() [edit on github]¶
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set_center
(*args, **kwargs) [edit on github]¶
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startup
(cache) [edit on github]¶ Called before a model may be evaluated multiple times.
See also
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teardown
() [edit on github]¶ Called after a model may be evaluated multiple times.
See also
setup()
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