Package astLib :: Module astSED :: Class SED

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Class SED

This class describes a Spectral Energy Distribution (SED).

To create a SED object, lists (or numpy arrays) of wavelength and relative flux must be provided. The SED can optionally be redshifted. The wavelength units of SEDs are assumed to be Angstroms - flux calculations using Passband and SED objects specified with different wavelength units will be incorrect.

The StellarPopulation class (and derivatives) can be used to extract SEDs for specified ages from e.g. the Bruzual & Charlot 2003 or Maraston 2005 models.

Instance Methods

__init__(self, wavelength=[], flux=[], z=0.0, ageGyr=None, normalise=False, label=None)

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SED object

copy(self)
Copies the SED, returning a new SED object

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loadFromFile(self, fileName)
Loads SED from a white space delimited file in the format wavelength, flux.

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writeToFile(self, fileName)
Writes SED to a white space delimited file in the format wavelength, flux.

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list

asList(self)
Returns a two dimensional list of [wavelength, flux], suitable for plotting by gnuplot.

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plot(self, xmin='min', xmax='max')
Produces a simple (wavelength, flux) plot of the SED.

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float

integrate(self, wavelengthMin='min', wavelengthMax='max')
Calculates flux in SED within given wavelength range.

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smooth(self, smoothPix)
Smooths SED.flux with a uniform (boxcar) filter of width smoothPix.

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redshift(self, z)
Redshifts the SED to redshift z.

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normalise(self, minWavelength='min', maxWavelength='max')
Normalises the SED such that the area under the specified wavelength range is equal to 1.

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normaliseToMag(self, ABMag, passband)
Normalises the SED to match the flux equivalent to the given AB magnitude in the given passband.

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matchFlux(self, matchSED, minWavelength, maxWavelength)
Matches the flux in the wavelength range given by minWavelength, maxWavelength to the flux in the same region in matchSED.

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float

calcFlux(self, passband)
Calculates flux in the given passband.

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float

calcMag(self, passband, addDistanceModulus=True, magType="Vega")
Calculates magnitude in the given passband.

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float

calcColour(self, passband1, passband2, magType="Vega")
Calculates the colour passband1-passband2.

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getSEDDict(self, passbands)
This is a convenience function for pulling out fluxes from a SED for a given set of passbands in the same format as made by mags2SEDDict - designed to make fitting code simpler.

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extinctionCalzetti(self, EBMinusV)
Applies the Calzetti et al.

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Method Details

copy(self)

Copies the SED, returning a new SED object

Returns: SED object: SED

loadFromFile(self, fileName)

Loads SED from a white space delimited file in the format wavelength, flux. Lines beginning with # are ignored.

Parameters:

fileName (string) - path to file containing wavelength, flux data

writeToFile(self, fileName)

Writes SED to a white space delimited file in the format wavelength, flux.

Parameters:

fileName (string) - path to file

asList(self)

Returns a two dimensional list of [wavelength, flux], suitable for plotting by gnuplot.

Returns: list: list in format [wavelength, flux]

plot(self, xmin='min', xmax='max')

Produces a simple (wavelength, flux) plot of the SED.

Parameters:

xmin (float or 'min') - minimum of the wavelength range of the plot
xmax (float or 'max') - maximum of the wavelength range of the plot

integrate(self, wavelengthMin='min', wavelengthMax='max')

Calculates flux in SED within given wavelength range.

Parameters:

wavelengthMin (float or 'min') - minimum of the wavelength range
wavelengthMax (float or 'max') - maximum of the wavelength range

Returns: float

relative flux

smooth(self, smoothPix)

Smooths SED.flux with a uniform (boxcar) filter of width smoothPix. Cannot be undone.

Parameters:

smoothPix (int) - size of uniform filter applied to SED, in pixels

redshift(self, z)

Redshifts the SED to redshift z.

Parameters:

z (float) - redshift

normalise(self, minWavelength='min', maxWavelength='max')

Normalises the SED such that the area under the specified wavelength range is equal to 1.

Parameters:

minWavelength (float or 'min') - minimum wavelength of range over which to normalise SED
maxWavelength (float or 'max') - maximum wavelength of range over which to normalise SED

normaliseToMag(self, ABMag, passband)

Normalises the SED to match the flux equivalent to the given AB magnitude in the given passband.

Parameters:

ABMag (float) - AB magnitude to which the SED is to be normalised at the given passband
passband (an Passband object) - passband at which normalisation to AB magnitude is calculated

matchFlux(self, matchSED, minWavelength, maxWavelength)

Matches the flux in the wavelength range given by minWavelength, maxWavelength to the flux in the same region in matchSED. Useful for plotting purposes.

Parameters:

matchSED (SED object) - SED to match flux to
minWavelength (float) - minimum of range in which to match flux of current SED to matchSED
maxWavelength (float) - maximum of range in which to match flux of current SED to matchSED

calcFlux(self, passband)

Calculates flux in the given passband.

Parameters:

passband (Passband object) - filter passband through which to calculate the flux from the SED

Returns: float

flux

calcMag(self, passband, addDistanceModulus=True, magType="Vega")

Calculates magnitude in the given passband. If addDistanceModulus == True, then the distance modulus (5.0*log10*(dl*1e5), where dl is the luminosity distance in Mpc at the redshift of the SED) is added.

Parameters:

passband (Passband object) - filter passband through which to calculate the magnitude from the SED
addDistanceModulus (bool) - if True, adds 5.0*log10*(dl*1e5) to the mag returned, where dl is the luminosity distance (Mpc) corresponding to the SED z
magType (string) - either "Vega" or "AB"

Returns: float

magnitude through the given passband on the specified magnitude system

calcColour(self, passband1, passband2, magType="Vega")

Calculates the colour passband1-passband2.

Parameters:

passband1 (Passband object) - filter passband through which to calculate the first magnitude
passband1 (Passband object) - filter passband through which to calculate the second magnitude
magType (string) - either "Vega" or "AB"
passband2 (Passband object)

Returns: float

colour defined by passband1 - passband2 on the specified magnitude system

getSEDDict(self, passbands)

This is a convenience function for pulling out fluxes from a SED for a given set of passbands in the same format as made by mags2SEDDict - designed to make fitting code simpler.

Parameters:

passbands (list of Passband objects) - list of passbands through which fluxes will be calculated

extinctionCalzetti(self, EBMinusV)

Applies the Calzetti et al. 2000 (ApJ, 533, 682) extinction law to the SED with the given E(B-V) amount of extinction. R_v' = 4.05 is assumed (see equation (5) of Calzetti et al.).

Parameters:

EBMinusV (float) - extinction E(B-V), in magnitudes