Sunday, November 2, 2014

Computing Emission Line Properties

The latest update to Galacticus v0.9.3 allows calculation of emission line luminosities for galaxies. Much of the work to make this happen was carried out by Pomona College student Gabe Currier over the summer of 2013. The calculation is based on the methodology of Panuzzo et al. (2003). Briefly, HII region models are constructed using Cloudy for a variety of gas densities and metallicities, and HI, HeI, and OII ionizing luminosities. Emission line luminosities are then computed by interpolating in these tables based on the instantaneous properties of model galaxies.

To compute emission line luminosities it is therefore necessary to run Galacticus including the following rest-frame luminosity filters at each redshift of interest: Lyc, HeliumContinuum, OxygenContinuum. This causes the ionizing luminosity for each three species to be computed and output.

Emission line luminosities can then be found using Galacticus's data extraction modules, by simply importing the Galacticus::EmissionLines module. Emission line luminosites (in units of Solar luminosities) can then be accessed as named properties using names such as  

   totalLineLuminosity:balmerAlpha6563:rest:z0.0000

which will return the Hα luminosity at z=0. Equivalent properties for disk and spheroid are provided (simply replace "total" with "disk" or "spheroid").

Currently available lines are:
 
  • balmerAlpha6563
  • balmerBeta4861
  • oxygenII3726
  • oxygenII3729
  • oxygenIII4959
  • oxygenIII5007
  • nitrogenII6584
  • sulfurII6731
  • sulfurII6716

Additionally, if a line is requested as

   totalLineLuminosity:balmerAlpha6563:<filterName>:rest:z0.0000

then the line luminosity is computed under the provided filter, and the luminosity is returned in units of maggies for easy conversion to AB magnitudes.