4.2. Pseudo-Databases: Searchable Collections of Catalogues
It should be kept in mind that object databases like SIMBAD, NED and LEDA, generally do not include the full information contained in the CDS/ADC collections of catalogues and tables. This is especially true for older tables which may have become available in electronic form only recently. The catalogues and tables frequently contain data columns not (yet) included in the object databases. Thus the table collections should be considered as a valuable complement to the databases. Different sites support different levels of search of those collections.
Probably the largest number of individual catalogues (~ 1560) that can be browsed from one site is that offered by VizieR at CDS (vizier.u-strasbg.fr). You may select the catalogues by type of object, wavelength range, name of space mission, etc. An advantage of VizieR is that the result comes with hyperlinks (if available) to SIMBAD or other relevant databases, allowing more detailed inquiries on the retrieved objects. A drawback is that a search on many of them at the same time requires selecting them individually by clicking on a button. An interface allowing searches through many or all of them is under construction.
The DIRA2 service (``Distributed Information Retrieval from Astronomical files'') at www.ira.bo.cnr.it/dira/gb is maintained by the ASTRONET Database Working Group in Bologna, Italy. It provides access to data from astronomical catalogues (see the manual at www.pd.astro.it/prova/prova.html). The DIRA2 database contains about 270 original catalogues of Galactic and extragalactic data written in a DIRA-specific ASCII format. The output of the searches are ASCII or FITS files that can be used in other application programs. DIRA2 allows one to plot objects in an area of sky taken from various catalogues onto the screen with various symbols of the user's choice. Sorting as well as selecting and cross-identification of objects from different catalogues is possible, but there is no easy way to search through many catalogues at a time. The software is publicly available for various platforms.
The ``CATalogs supporting System'' (CATS; cats.sao.ru) has been developed at the Special Astrophysical Observatory (SAO) in Russia. Apart from dozens of the larger general astronomical catalogues it offers the largest collection of radio source catalogues searchable with a single command (see chapter on Radio Astronomy by H. Andernach in these proceedings). A search through the entire catalogue collection ``in one shot'' is straightforward.
A set of about 100 catalogues, dominated by X-ray source catalogues and mission logs, can be browsed at the ``High Energy Astrophysics Science Archive Research Center'' (HEASARC) at heasarc.gsfc.nasa.gov/W3Browse. The same collection is available at the ``Leicester Database and Archive Service'' (LEDAS; ledas-www.star.le.ac.uk).
A similar service, offered via telnet and without a web interface, is the ``Einstein On-line Service'' (EOLS, or EINLINE) at the Harvard-Smithsonian Center for Astrophysics (CfA). It was designed to manage X-ray data from the EINSTEIN satellite, but it also served in 1993/94 as a testbed for the integration of radio source catalogues. Although EOLS is still operational with altogether 157 searchable catalogues and observing logs, lack of funding since 1995 has prevented any improvement of the software and interface or the integration of new catalogues.
NASA's ``Astrophysics Data System'' (ADS) offers a ``Catalog Service'' at adscat.harvard.edu/catalog_service.html. With the exception of the Minnesota Plate Scanning project (APS, cf. Section 5.1), all available 130 catalogues are stored at the Smithsonian Astrophysical Observatory (SAO). For a complete list, request ``catalogues by name'' from the catalogue service. Not all available catalogues can be searched simultaneously. The service has not been updated for several years and will eventually be merged with VizieR at CDS.
A growing number of catalogues is available in datOZ (see 146.83.9.18/datoz_t.html) at the University of Chile as described in [Ortiz (1998)]. It offers visualization and cross-correlation tools. The STARCAT interface at ESO (arch-http.hq.eso.org/starcat.html) with only 65 astronomical catalogues is still available, but has become obsolete. ASTROCAT at CADC (cadcwww.dao.nrc.ca/astrocat) offers about 14 catalogues.