Return to directory of Todd's tools

Convert flux density, beamsize, and frequency to brightness temperature (both the Rayleigh-Jean and Planck values). If a distance is specified, it also computes the blackbody luminosity for this brightness temperature. If tdust is also specified, it also computes dust opacity, gas mass, and column density of particles.


tt.brightness(fluxDensity=None, frequency=None, beamsize=None, beamsize2=None, 
                distance=None, tdust=None, R=100, fluxDensityUncertainty=0,
                beamsizeUncertainty=0, beamsize2Uncertainty=0, trials=2000, 
                kappa=None, tdustUncertainty=0, calibrationUncertainty=0,
                columnDensity=None, img=None, pixel=None, bunit=None, pixels=False)
Required parameters:
  • None, but a combination of (fluxDensity, frequency, beamsize) or (img) is required
Optional parameters:
  • fluxDensity: Jy
  • frequency: string with units, or floating point GHz
  • beamsize: arcsec
  • beamsize2: second dimension of beamsize
  • distance: in kpc
  • tdust: dust temperature (K)
  • R: gas to dust mass ratio (default=100) . The Hydrogen molecule mass used is 2.33*mass_proton.
  • fluxDensityUncertainty: in Jy
  • beamsizeUncertainty: in arcsec
  • beamsize2Uncertainty: in arcsec
  • trials: the number of Monte Carlo simulations to run to determine Tb uncertainty
  • kappa: the dust mass opacity coefficient to use (None: automatic: 1.84 cm2/g at 342GHz extrapolated with beta=2)
  • tdustUncertainty: in K
  • calibrationUncertainty: to be used for the mass calculation only, add in quadrature to the fluxDensityUncertainty
  • columnDensity: if provided, compute the abundance relative to H2 (based on R)
  • img: the image to use to grab the fluxDensity (and frequency,beamsize,bunit if not given)
  • pixel: the pixel to grab from img
  • bunit: the bunit of img, in case it is not present in the header
  • pixels: if True, then treat the beamsizes as pixel sizes and compute their solid angle

  • dictionary containing keys: 'temperature', 'temperaturePlanck'
  • If distance is given, it also returns 'stefanBoltzmannLuminosity', 'stefanBoltzmannLuminosityUncertainty', and 'dustLuminosity' (in units of Lsun, using the Planck temperature)
  • If tdust is also given, it also returns 'tau', 'mass', 'massUncertainty', and 'columnDensity'.
  • The columnDensity is that of particles. If you want N(H2), then divide the result by 1.2


CASA <2>: au.brightness(1,300,1)
  Out[2]: [13.6, 19.946560339492333]
-- ToddHunter - 2014-01-06
Topic revision: r11 - 2015-03-12, ToddHunter
This site is powered by FoswikiCopyright © by the contributing authors. All material on this collaboration platform is the property of the contributing authors.
Ideas, requests, problems regarding NRAO Public Wiki? Send feedback