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Continuum observations (Single Continuum)

Select the Single continuum option in the Spectral Type section of the Spectral Setup editor pane. You will then be asked to specify a single frequency to be used in the spectral setup either in the rest or the sky frame. If you specify a rest frequency, the frequency on sky will be automatically computed for each of your sources based on their velocity, however if you specify a sky frequency this will remain the same for all sources regardless of their velocity. The details of the spectral windows computed by the OT based on your input continuum frequency for each baseband can be found in the spectral window tables. The representative frequency (used for the time estimate calculations as well as the antenna beamsize) defaults to the centre of the first spectral window. You should verify that this is an appropriate choice and if not (e.g. if it falls in an area of low atmospheric transmission) modify it. You can change the spectral window of the representative frequency using the radio buttons in the spectral window table and change the value of the representative frequency within that spectral window by editing the Representative Frequency box below the tables.

In the Spectral tab you can graphically visualise the spectral configuration (see Fig. 3.3). The proposed sidebands are shaded in yellow, while the frequency ranges and the central frequencies of the spectral windows are respectively indicated by the horizontal and the vertical blue lines labelled Continuum. Since the continuum setting is designed to maximise the spectral bandwidth covered, the spectral windows completely cover the width of the sidebands. Note that the continuum frequency specified actually corresponds to the LO frequency and is not itself observed in bands 3,6 and 7. In Band 9, the continuum frequency specified corresponds to the frequency at the centre of an 8 GHz wide sideband.

Figure 3.3: Visualisation of continuum observations in the spectral editor pane.
Image Img04


next up previous contents
Next: Observing line transitions (Spectral Up: Configure the spectral setup Previous: Configure the spectral setup   Contents
The ALMA OT Team, 2013 Feb 27