1.2.1.0 componentlist.setspectrum

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componentlist.setspectrum - Function

1.2.1 Change the spectrum of the component

Description

The setspectrum function changes the spectrum of the specified components to the user specified spectrum.

The type argument defines what the sort of new spectrum to use. This can be either ’constant’or ’spectral index’. The parsing of this string is case insensitive.

If the spectrum type is ’constant’ then the remaining arguments in this function are ignored. There are no other parameters needed to specify a constant spectrum.

But if the spectrum is ’spectral index’, the ’index’ argument is needed to fully specify the spectrum by using the index argument.

If the spectrum is ’tabular’, then ’index’ is ignored but the three parameters ’tabularfreqs’, ’tabularflux’ and ’tabularframe’ are considered. ’tabularfreqs’ and ’tabularflux’ have to be list of same lengths and larger than 2. You need at least 2 samples to interpolate the spectral value in between. The flux of the source is interpolated from these values. Extrapolation outside the range given in ’tabularfreqs’ is not done.

’tabularfreqs’ should be float values in ’Hz’ ’tabularflux’ should be float values in ’Jy’

You should ensure that the reference frequency is set to the value you desire, using the setfreq function if you change to the spectral index shape.

Arguments


Inputs
which	The index specifying the component to modify. A value between 0 and one less than the list length, inclusively
	allowed:	int
	Default:
type	The new spectrum type. A string that is either ’constant or ’spectral index’ or ’tabular’
	allowed:	string
	Default:	spectral index
index	The spectral index.
	allowed:	double
	Default:	0.0
tabularfreqs	The frequencies of for the tabular values, in Hz
	allowed:	doubleArray
	Default:	1.0e11
tabularflux	tabular flux density values, in Jy (same length as tabularfreqs)
	allowed:	doubleArray
	Default:	1.0
tabularframe	The frame for which the frequencies given are in
	allowed:	string
	Default:	LSRK

Returns
bool

Example

      cl.open(’centarusA.cl’)
      cl.setspectrum(2, ’spectral index’, -0.5)
      print cl.getcomponent(2)[’spectrum’][’index’]
      cl.done()

      This example revises the model for Centaurus-A changing the
      spectral index of all the components in the left lobe. The
      output from the print statement is "[-0.5 0 0 0]"

      cl.addcomponent(shape=’point’, flux=[1.0, 0.0, 0.0, 0.0], dir=’J2000 19h00m00 -20d00m00’)
      cl.setspectrum(which=0, type=’tabular’, tabularfreqs=[1.0e9, 1.1e9, 1.4e9], tabularflux=[1.0, 0.9, 0.75])
      cl.rename(’my19hcomp.cl’)
      cl.done()

      In this example a component is created from scratch as a point
      source The spectrum is set to, say, measured values at 3
      frequencies (1GHz, 1.1GHz and 1.4GHz) to 1.0Jy, 0.9Jy, 0.75Jy
      respectively.  Any frequency in between the range 1 to 1.4 GHz
      the flux will be estimated by interpolation.

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