This documentation manual covers the basic usage of the Weeds extension. More detailed information on each command is available using the Gildas online help, e.g.:
[fontsize=\scriptsize] LAS90> help modsource WEEDS\MODSOURCE = "python weeds/modsource.py" [WEEDS\]MODSOURCE MODFILE ANTSIZE [/TCONT TCONT] [/OPACITY I] [/KEEPCONT] [/VERBOSE] Model the emission of a source assuming local thermodynamic equilibrium (LTE). The model paramaters (column density, kinetic temperature, source size, line width and velocity offset for each species) are read from MODFILE. The modeled brightness temperature is stored in the TB_MODEL memory. For convenience the current spectrum is also stored in a memory, OBS, so one can easily overplot the result of the model on the observed spectrum. See the documentation manual for more details on the computa- tion. Arguments: MODFILE the name of the file containing the parameters. The file must have one line per species with at least six columns containing respectively: 1) The species name 2) The column density for this species in cm-2 3) The excitation temperature in K 4) The source size in arcsec 5) The offset velocity from the source VLSR, in km/s 6) The line FWHM in km/s One additional column may be used to select a different origin for each species: 7) The origin of this species (e.g. JPL or CDMS). If emp- ty, species with any origin are selected. The following options may be used at the end of the line: /ABSORPTION If this option is set, the component is as- sumed to be a foreground layer. /PARTFUNC Q Set the log10 of the partition function at the excitation temperature to Q. If not set, the partition function values (log-log interpolated/extrapolated at the excitation temperature) from the selected database are used. Lines that start with a "!" are treated as comments. ANTSIZE the antenna size in meters Options: /TCONT set the continuum level to TCONT, in K. Default is 0. /OPACITY I store the opacity of the Ith component in the TAU_MODEL memory. Components are numbered in the same order as in MODFILE, starting from 1. /KEEPCONT do not remove the continuum from the final spectra. /VERBOSE print partition function, line frequencies, upper level energies and degeneracies, Einstein coefficients and opac- ities at the line centers.
For a more detailed description of the Weeds extension, we refer the interested reader to Maret, Hily-Blant, Pety et al., Astronomy & Astrophysics 526, A47 (2011). This paper describes the implementation of the extension, and gives more details about the spectroscopic databases that it uses, and explains how spectra are modeled.
Weeds developers can be contacted by email at gildas@iram.fr. Bug reports should also be sent to this address.