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This function computes the ratio of the current CASA primary beam correction scheme (10.7m Airy disk) to the current best ALMA Gaussian primary beam model. See also primaryBeamArcsec and gaussianBeamOffset.


au.almaPrimaryBeamCorrection(frequency, radius, diameter=12.0, taper=10.0,
                              obscuration=0.75, verbose=False, showEquation=False,
                              use2007formula=True, fwhmfactor=None)
Inputs: * frequency: in Hz or GHz (GHz assumed for values < 1000), float or string with untis * radius: in arcseconds from the phase center Parameters passed to au.primaryBeamArcsec: * diameter: meters * taper: dB * obscuration: meters * fwhmfactor: alternative to taper: fwhmfactor*lambda/D * use2007formula: Boolean * showEquation: Boolean * verbose: Boolean Returns:
  • The value by which to scale a flux density measured at this radius in a CASA primary-beam corrected image.


An extreme case: ALMA 100 GHz image from the 12m antennas, with a source located 45 arcsec from the phase center.
ASA <2>: au.almaPrimaryBeamCorrection(100,radius=45)
CASA Airy gain = 0.165, true gain = 0.192, ratio = 0.864
After CASA primary beam correction, scale the flux of the source by the ratio.
  Out[2]: 0.86366997716369387

-- ToddHunter - 2015-01-31
Topic revision: r2 - 2016-01-07, ToddHunter
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