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Single Continuum

The Single Continuum interface essentially provides a shortcut to producing a spectral setup that covers the maximum possible bandwidth with the lowest possible spectral resolution. It is not expected that this interface will be used to observe spectral lines. For the expected source properties, only a continuum flux must be entered.

After selection of a receiver band each baseband receives a 2 GHz-wide TDM spectral window, each of which has an effective bandwidth of 1875 MHz. For bands that have 2SB receivers e.g. bands 3, 4, 6, 7 and 8, two will be placed in each sideband. For band 9, which is a DSB receiver, all four are placed in the same sideband and the same discussion about avoiding the image-sideband equivalents mentioned in Section 5.3.3.1 applies.

The default spectral window frequencies have been chosen such that the continuum sensitivity is maximised and prominent atmospheric absorption features avoided. For most projects these defaults should be chosen. It is possible to choose a different set of spectral windows by entering a central (average) frequency (in the observed/sky frame) although this cannot be done if full polarization has been selected.


Table 5.1: Default single continuum frequencies for the available receiver bands.
Band Spectral window frequencies (GHz) Central frequency (GHz)
3 90.5, 92.5, 102.5, 104.5 97.5
4 138, 140, 150, 152 145
6 224, 226, 240, 242 233
7 336.5, 338.5, 348.5, 350.5 343.5
8 398, 400, 410, 412 405
9 676, 678, 680, 682 679

The Representative Frequency will default to being the central (sky) frequency of the first spectral window. As with the spectral line interface, this can be changed, both by changing the spectral window and the frequency within this window. However, it is not possible to change the other parameters of the individual spectral windows. These can only be changed by editing the single value of the sky frequency.

Spectral averaging is not available for Single Continuum as the spectral resolution is already relatively low.


next up previous contents
Next: Spectral Scan Up: Spectral Setup Previous: Spectral Line   Contents
The ALMA OT Team, 2014 May 21