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Single Continuum

The Single Continuum interface automatically creates four spectral windows located such that they cover the maximum possible bandwidth. The default centre frequencies are also placed such that the atmospheric transmission is maximised and thus the single-continuum interface is ideally suited to providing the highest-sensistivity continuum maps of a source. For 2SB receivers (bands 3-8) two spectral windows are placed in each sideband. For bands 9 and 10 (DSB) all four are placed in the same sideband. If necessary, the frequencies of the spectral windows can be changed by setting a different average frequency i.e. the relative positions of the spectral windows is fixed.

The Representative Frequency (Section 5.3.3.7) will default to being the central (sky) frequency of the last spectral window. As with the spectral line interface, this can be changed, both by selecting a different spectral window and by moving the frequency within this. However, it is not possible to change the other parameters of the individual spectral windows.

As the same suggests, Single Continuum setups are intended for continuum observations and thus were previously only allowed using low spectral-resolution spws i.e. the TDM correlator mode. It is now possible to instead select FDM mode - this covers the same bandwidth but has significantly higher spectral resolution. This can be useful when observing a continuum that is contaminated with spectral lines which must be removed during data processing. This significantly increases the size of a dataset and so should only be selected if absolutely necessary. If the FDM mode has been selected, spectral averaging of the spws is possible.

For solar and VLBI observations, the use of Single Continuum is currently enforced and the frequencies of the spectral windows are fixed i.e. it is only possible to select which band one wants to observe in, not what the spw frequencies within the band are.


next up previous contents
Next: Spectral Scan Up: Spectral Setup Previous: Representative Frequency   Contents
The ALMA OT Team, 2021 Feb 03