Introduction
The access to LEDA from Aladin allows to display the galaxies in a field centered on coordinates or on an object specified by its designation. This chart may be overlayed to an image from the DSS, Vizier database or any FITS image.
Access by designation
When a name is provided to Aladin, its position is searched in Simbad and LEDA
is searched around this position. Therefore, note that (i) the target may not
be correctly centered (or even not found) because the position assigned in
LEDA may differ from the Simbad position and (ii) if the object's name is not
recognized by Simbad the position can not be determined, even if this name is
indexed in LEDA. In case of problem, give the coordinates of the target.
Additional constraints
It is optionally possible to specify additional constraints to filter the list of
galaxies returned by LEDA.
LEDA allows SQL selection on about 100 parameters. SQL is the
query language used by database systems, you may easily find good manuals on
the WEB. In practice the constraint passed from Aladin is attached with the
where clause of the request.
Examples of possible additional constraints are:
- v<5000
Select only the objects with velocity lower than 5000 km/s
- v<5000 and t<0
Select early-type galaxies nearer than v=5000 km/s
Consult the list of parameters to prepare your request.
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