Rest Frequency

ASAP reads the line rest frequency from the RPFITS file when reading the data. The values stored in the RPFITS file are not always correct and so there is a function set_restfreq to set the rest frequencies.

For each integration, there is a rest-frequency per IF (the rest frequencies are just stored as a list with an index into them). There are a few ways to set the rest frequencies with this function.

If you specify just one rest frequency, then it is selected for the specified source and IF and added to the list of rest frequencies.

  # Select for specified source/IF
  ASAP> scans.set_restfreqs(freqs=1.667359e9, source='NGC253', theif=0)

  # Select for all sources and IFs
  ASAP> scans.set_restfreqs(freqs=1.667359e9)

If you specify a list of frequencies, then it must be of length the number of IFs. Regardless of the source, the rest frequency will be set for each IF to the corresponding value in the provided list. The internally stored list of rest frequencies will be replaced by this list.

  # Set rest frequency for all IFs
  ASAP> scans.set_restfreqs(freqs=[1.6654018e9,1.667359e9,])

In both of the above modes, you can also specify the rest frequencies via names in a known list rather than by their values.

Examples:

  ASAP> scans.lines()                 # Print list of known lines
  ASAP> scans.set_restfreqs(lines=['OH1665','OH1667'])