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Calibrator Selection Tool

Calibrators can be added to both Phase-1 proposals and Phase-2 programs using a standard calibrator search tool, although the details of how this works differs slightly in the two cases. Two catalogues can be searched: the full ALMA calibrator database that is searched online, or a much more limited version (smaller and not so up-to-date) that is contained within the OT and thus can be searched even in the absence of a network connection. The former is of course recommended and is the default. The internal catalogue is basically a snapshot of the SMA catalogue taken a few years ago and contains measurements at 3, 1 and 0.87 mm. The ALMA catalogue also contains these SMA data, but also VLA measurements at lower frequencies. Most importantly, new measurements taken with ALMA are now constantly being added.

Figure 7.5: The Calibrator Selection Tool as used in the Calibration Setup of Science Goal. A search has been made for all calibrators within a 10-degree radius of a source position, that have a flux greater than 500 mJy in ALMA Band 3.
Image CalibratorTool

The search interface is shown in Figure 7.5. Calibrators are found by matching a set of search criteria, consisting of the centre position and radius of a cone search and a set of minimum and maximum values for the flux as well as the frequency over which this is valid. Criteria are enabled by the presence of non-zero values and a symbol next to the field will give a visual sign of whether a particular feature is enabled or not. Searching with all filters disabled will return the entire catalogue! A final field sets how many matches will be returned. From the total number of sources that match the search criteria, these will always be those with the lowest values of Right Ascension.

Once the search constraints have been entered, either the ALMA online catalogue or the internal OT catalogue can be searched by clicking the ``Submit Query'' button. As with many other tables in the OT, the results can be sorted by clicking on a column header; the direction of the arrow indicates the sort order which can be reversed with subsequent clicks. Secondary sorts are not possible. Alternatively, the OT's list of non-sidereal calibrators can be displayed.

The calibrator tool can be accessed in a number of ways. At Phase 1, it is only available when defining a user-defined calibration in a Science Goal. However, at Phase 2, it is also available from the Tool menu and from within a Field Source definition. In all cases, the search interface itself works identically, although the details of how a chosen source is used vary. Please consult the relevant sections of this manual for more information.


next up previous contents
Next: LO Configuration Tool Up: Tools Previous: Archive Search Tool   Contents
The ALMA OT Team, 2016 Aug 23