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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.