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Resolving source information

The querying (or ``resolving'' in OT parlance) will work once a source name has been entered. The OT will first try SIMBAD and then, if no result is forthcoming, NED. It is not possible to select which server is queried although the OT will state which one gave the displayed result. In the case of SIMBAD, the OT performs a so-called ``basic query''. The safest method is to enter a non-ambiguous catalogue/survey name such as Cen A, NGC 5128, Arp 153, etc. Catalogue/survey names that include coordinates are okay as well e.g. PKS J1325-4303. Note that searches based on coordinates alone e.g. 1325-4303 are totally disallowed as they hardly ever return the right source.

It is possible to search for a source using the so-called IAU format i.e. a source name based on the source coordinates and an equinox indicator e.g. J1325-430. This type of search is entered as ``iau J1325-430'', but should usually be avoided as it will usually return the wrong source (SIMBAD returns several sources around the implied position and the OT simply takes the first one). Inserting an ``object type'' can though make this a fairly useful search option e.g. ``iau J1325-430=QSO''. The name should though be changed to something more sensible once the correct source has been found.

Be careful with the proper motions of bright quasars. The Hipparcos mission measured non-zero values for many of these although, reassuringly, the associated uncertainties mean that the results are consistent with zero. Nonetheless, it is the measured, non-zero, values that will be entered into the OT. Parallax can also sometimes be negative, but again this is due to the measurement uncertainties.

Although an extremely useful tool resolving source information should be used with care and all details should be checked very carefully. The OT will present a table containing the source information that has been resolved, before this is entered into the Field Setup form. This will warn the user if proper motions or a velocity have not been found and will also give the actual name of the source contained within the database (as opposed to the one that was used for the search). If the OT is unable to resolve a source and the details of a source had previously been entered, it will bring up a dialogue asking whether the name should be reset to the previous source or whether the failed search term should be left for editing.

Please note that the user has ultimate responsibility to ensure that the source details are correct!


next up previous contents
Next: Field definitions Up: Field Setup Previous: Source properties   Contents
The ALMA OT Team, 2014 May 21