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THE NASA/IPAC EXTRAGALACTIC DATABASE

(Version Date: January 12, 1997)

I. INTRODUCTION TO NED

The NASA/IPAC Extragalactic Database (NED) has been providing computer-network access to a broad range of published extragalactic data since June 1990. NED offers (1) an X-Windows Graphical User Interface (GUI) with point-and-click, mouse-driven menus, as well as graphics and image-display capabilities, (2) a VT100 ASCII-character menu, (3) a server mode, and (4) as of January 1997, a WWW-based version. The GUI interface provides greater functionality and display capabilities, but its speed is critically dependent upon the network bandwidth; the VT100 mode and the WWW-based versions are generally faster. NED is currently supporting about 4-5,000 interactive sessions per month, in addition to some 20,000 server-mode sessions per month.
NED is continuously being augmented and updated. NED represents the systematic merger of both major catalogs of extragalactic objects covering all wavelengths and also scores of shorter lists, culled from published journal articles. New catalogs and lists are continually being folded into NED, with each undergoing a detailed process of cross-identification for individual objects. Important recent additions include extragalactic supernovae, the FIRST, 7C, MRC, B3, Texas, PMN and PMNM radio source surveys, the APM Bright Galaxy Catalog, the Catalog of Faint Galaxies at the North Galactic Pole, Southern Ringed Galaxies, and the Las Campanas Redshift Survey.

II. THE NED DATABASE

The most recently updated version of the NED database contains POSITIONS, BASIC DATA, and over 1,224,800 NAMES for 746,000 EXTRAGALACTIC OBJECTS, as well as some 813,000 BIBLIOGRAPHIC REFERENCES to 30,000 PUBLISHED PAPERS, and 37,000 NOTES FROM CATALOGS and other publications. NED supports searches for objects and references, and offers browsing capabilities for more than 14,500 ABSTRACTS of articles of extragalactic interest that have appeared in A&A, AJ, ApJ, MNRAS, and PASP since 1988, and in Publications of the Astronomical Society of Japan, Astronomy Reports and Astronomy Letters (formerly Soviet Astronomy and Soviet Astronomy Letters), Nature, and IAU Circulars since 1992.
Over 1,000,000 detailed PHOTOMETRIC MEASUREMENTS taken from catalog and the published literature are currently available in NED both as lists and plotted spectral energy distributions (SEDs). Also on-line are THESIS ABSTRACTS of DOCTORAL DISSERTATIONS on extragalactic topics. Title and abstract searches of the NED literature database can now be made by specifying author names. It is also possible to search the main NED database for objects selected by REDSHIFT (NED currently has over 93,300 velocities, with detailed reference frames being added continuously), as well as the selection by CATALOG PREFIX, by POSITION or by TYPE (e.g., QSO or infrared source). Once found, SKYPLOTS can be produced for the objects and saved as POSTSCRIPT files, or displayed directly within the GUI.

III. ACCESSING NED VIA TELNET

telnet ned.ipac.caltech.edu
NED can be accessed over the INTERNET provided users have at least a VT100 terminal, or VT100 emulation software, (e.g., an `X-term' window on a workstation) for the character-based interface; or X-Windows running on workstations for the GUI. A connection can be obtained with the command: telnet ned.ipac.caltech.edu . Once connected to the NED platform and prompted for a "login:", please respond with NED (no password is required) and follow the interface options and instructions provided. The NED user interface is designed to be self- documenting, especially through the HELP utilities. First-time users may want to read the TUTORIAL in the News and Information section of the interface.
At any time during a session NED will forward to the user, upon request, files containing data retrieved during that session. Alternatively, NED also provides batch processing capabilities on input files submitted through electronic mail (see the BATCH JOB option and associated HELP in the Main Menu).
This work is being carried out by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration, Office of Space Science.

ANNOUNCING THE WORLD-WIDE-WEB INTERFACE TO NED

http://nedwww.ipac.caltech.edu
NED is now available over the World-Wide Web. To use this version of NED, simply point your WEB browser at http://nedwww.ipac.caltech.edu. Because of the form-based nature of this WEB interface, certain interactive plotting features of the X interface are not yet supported; however, new functionality is provided and the response of the interface as seen by the user is much increased. The first new feature to be introduced with the Web version of NED is the ability to search for, preview, and retrieve multi-wavelength images.

IV. RECENT FEATURES IN NED

In addition to adding new data and staying current with the literature, the NED Team is committed to providing new functionality so as to make the data holdings of NED more useful and accessible as a research tool for astronomers. We outline below some of those more recent tools, but also highlight other features which may have escaped the casual user's attention.
(i) SPECTRAL ENERGY DISTRIBUTION PLOTS
Within the PHOTOMETRIC DATA frame it is both possible to obtain detailed listings of photometric data associated with the objects in NED, and to interactively view these data plotted as spectral energy distributions (SEDs). After requesting the data, SEDs can be made with a variety of plotting options (F_{nu} or {nu}F_{nu} versus {lambda} or {nu}) user-defined scales and magnifications. Individual points (or groups of points) can be interrogated, identified and replotted with or without error bars, etc. POSTSCRIPT versions of selected plots can also be saved, and then retrieved from an anonymous ftp account by the user. [Note: Interrogation of the SED plots is not available in this first release of the Web interface.]
(ii) REDSHIFT and POSITION FRAMES
Analogous to the "Photometric Data Frame", NED now provides a "Redshift Frame" and a "Position Frame" which detail individually published radial velocity or position, respectively, for objects in NED.
(iii) PARAMETER-CONSTRAINED SEARCHES
The `By Parameter Search' capability allows users to filter the entire NED database by parameters such as redshift, object type, and/or name prefix, with or without constraints on where in the sky these objects are found.
(iv) AUTHOR NAME SEARCH
In the Main Menu (entry level) under the Literature Column, there is a button labeled `Authr Name'. Choosing this option presents the user with a new screen which searches the NED literature database (either papers or theses) for an author's surname. Abstracts may then be e-mailed to X-Window users; while from the Web interface users can capture the abstracts directly.
(v) OBJECTS IN REFERENCE SEARCH
Within the Reference Data Screen a new feature centrally located at the top of the screen now allows NED users to retrieve a listing of all extragalactic objects within NED that are referenced in a particular paper. Alternatively, when an Abstract is displayed the objects in that paper may be retrieved.
(vi) COORDINATE CALCULATOR
Under the Miscellaneous Column in the Main Menu the Coord Calc button activates a flexible interactive coordinate conversion calculator which includes full position-angle transformations when working between any of four coordinate systems (Equatorial, Ecliptic, Galactic and SuperGalactic) and any applicable equinox.
(vii) SEARCH BY IAU FORMAT
Many extragalactic (especially radio) sources are designated according to a positional naming scheme devised by the IAU. However, strict enforcement of this convention is not always possible, and numerous variations have been published. In order to recover these objects, the IAU FORMAT button allows NED users to spawn a positional search by IAU `name' with the appropriate search radius being calculated by the software.
(viii) ENVIRONMENT
Within the Environment screen NED users can tailor various aspects of their interactive session. By activating the Environment button on the Main Menu users can specify any combination of astronomical input/output coordinate systems and equinox. And, in that same frame, sorting options can be chosen, the extended name search can be toggled, and recession-velocity display units can be set to km/sec or redshift.
(ix) SKY PLOT
Once identified by NED, an object or list of objects can be plotted (at a variety of scales) on the screen (in X-windows mode) or saved for the user as a Postscript file for plotting on a local laser printer. Sky Survey scale is the default and SAO stars are optionally plotted for registration. Other scaling options are available.
(x) MEETINGS
A current listing of all astronomical meetings can be found in the NEWS AND INFORMATION window accessible from the Miscellaneous Column in the Main Menu. These listings are prepared by Liz Bryson (CFHT Librarian) and made available through NED on a monthly update basis. NED Users are encouraged to use the COMMENTS option in the interface to leave messages or suggestions. In case of problems that require special attention, you should contact any of the following: George Helou, Barry F. Madore, or Marion Schmitz at (818) 397-9594.